Mitotane treatment for adrenocortical carcinoma: an overview

S. DE FRANCIA 1, A. ARDITO 2, F. DAFFARA 2, B. ZAGGIA 2 A. GERMANO 2, A. BERRUTI 3, F. DI CARLO 1

Adrenocortical carcinoma (ACC) is a rare ag- gressive endocrine neoplasm characterized by a 5-year survival of less than 50%. Due to the widespread use of imaging techniques in clinics, ACC is increasingly recognized as an incidentally discovered tumor. Mostly charac- terized by poor prognosis, ACC is often diag- nosed at an advanced stage of disease. Early diagnosis is uncommon; when diagnosed, ACCs are usually large and have invaded ad- jacent organs, even if metastatic spread to distant sites can be absent. Complete surgi- cal resection is the only potentially curative treatment for patients with localized disease; however, due to a recurrence rate of 50-70% after apparent radical surgery, there is a strong rationale for a concomitant systemic treatment. Adrenolytic therapy with mitotane (o,p>-DDD), administered alone or in combi- nation with others antineoplastic agents, is the primary treatment for patients with ad- vanced ACC and is increasingly used also in an adjuvant setting, even if controversy ex- ists on this issue due to the limitations of the available literature. Despite being in use for many years, the rarity of ACC precluded the organization of randomized trials; thus, many areas of uncertainty and controversy remain regarding the role of this old drug in the clinical management of patients with ACC. The purpose of this paper is to review the current evidence on mitotane treatment in patients with advanced disease and in ACC

1Unit of Clinical Pharmacology Department of Clinical and Biological Sciences S. Luigi Hospital, University of Turin, Italy 2Internal Medicine, Department of Clinical and Biological Sciences S. Luigi Hospital, University of Turin, Italy 3Medical Oncology, Department of Clinical and Biological Sciences S. Luigi Hospital, University of Turin, Italy

patients after complete surgical resection as adjuvant treatment.

Key words: Endocrine gland neoplasms - Adrenocortical carcinoma - Mitotane, toxicity.

A drenocortical carcinoma (ACC) is a rare disease. Adrenal masses are among the most frequent tumors in humans, the major- ity of them found incidentally. However it is well established that about 80% of these incidentally detected adrenal masses rep- resent hormonally inactive adrenal adeno- mas, while only a small minority are ACCs.1- 3 Data obtained from the National Cancer Institute Survey from the early 1970s esti- mated an incidence of 1-2 per million pop- ulation per year, leading to 0.2% of cancer deaths in the United States.4 However, data from European ACC Registry, as the Ger- man one, suggest that the incidence is >1 per million 5 and may be even higher. An

Corresponding author: S. De Francia, Unit of Clinical Pharmacology, Clinical and Biological Sciences Depart- ment, S. Luigi Hospital, University of Turin, Regione Gon- zole 10, 10043 Orbassano, Turin, Italy.

E-mail: silvia.defrancia@unito.it

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exceptionally high annual incidence of ACC has been reported for children in southern Brazil, with 3.4-4.2 affected patients per 1 million children versus an estimated world- wide incidence of 0.3 per million children younger than 15 years.6-8 Some reports in- dicate a bimodal age distribution with a first peak in childhood and a second higher peak in the fourth and fifth decade.9 Euro- pean data, based on the low incidence of malignancies in children, report a relative peak of ACC incidence in the childhood be- low the age of ten, while for the second peak median age is 46 years (range 0.3-86). Women are more often affected than men (ratio 1:5),10-16 leading to the hypothesis that sex hormones may have an influence on ACC tumorigenesis. Interestingly, this fe- male predominance seems to be true only for functional tumors.16, 17 Data on the as- sociation of risk factors and the develop- ment of ACC are rather scarce. The best data were derived from a case-control study based on the National Mortality Followback Survey, which included a questionnaire sent to the next of kin of almost 20,000 deceased adults in the United States. In these study, 176 patients who died of adrenal cancer (the majority of them suffered most likely from ACC) were compared with 352 con- trols. Among women, an increased risk for developing ACC was found for ever users of oral contraceptives, especially for those who used them before the age of 25.

In addition, the above mentioned survey suggested an increased risk for developing ACC in male heavy smokers, but not in fe- male smokers. 17

No clear association was found for alco- hol use, height and weight, or food con- sumption patterns in either sex.17

In early series, the majority of patients were diagnosed with advanced disease. In a meta-analysis by Wooten and King 18 in- cluding more than 600 patients, published between 1952 and 1992, less than one third of the patients had localized disease (stage I or II) and 49% of patients were described as stage IV. In contrast, in more recent studies the percentage of patients in stage I or II is much higher, reflecting earlier diagnosis due

to widely available advanced imaging tech- nology.10, 13, 19, 20 Patients with stage I that were virtually nonexistent in older studies, now account for more than 5% of patients in ACC cohorts, most often presenting with an incidentaloma.20 Nevertheless, median tumor size is still >11 cm (range 3-40).11 Al- though one would expect an equal distribu- tion between right and left adrenal, some series report a slightly higher frequency of left-sided tumors.10, 16, 21 Bilateral tumors are extremely rare, and it is often not clear whether these tumors are independent of each other or if one represents a metasta- sis to the contralateral ACC. Several studies have confirmed that liver and lung are the two most frequent sites for metastases.9, 11, 16, 19 However, bone metastases leading to fractures and pain have been reported as presenting clinical feature in some patients with advanced ACC.22, 23

Related to prognosis, ACC-related deaths are rare, when calculated on a population basis. However, in affected patients mortal- ity from ACC is substantial. In different se- ries, 5-year overall survival ranged between 16% and 44%.13, 15, 19, 21, 24-28 Prognosis of ACC, poor on average, is still mainly de- pending on tumor stage, and 5-year survival rates were 79% for stage I, 62% for stage II, 50% for stage III, and 17% for stage IV.

Mitotane characteristics and pharmacokinetics

Mitotane (o,p’-DDD) is a chemical con- gener of the insecticide DDT (Figure 1). It is the only antineoplastic agent specifi- cally indicated for treatment of advanced ACC and specifically approved for this use by the Food and Drug Agency and by the European Medicine Executive Agency.29, 30 Mitotane, commercially available as Lyso- dren , 500 mg tablets (Bristol Myers Squibb and HRA Pharma), acts as an adrenocor- tical suppressant and as a steroid synthe- sis inhibitor. Mitotane is a white crystalline powder with a slight aromatic odor, practi- cally insoluble in water, soluble in alcohol and in ether, 10% soluble in oil or fat. Mito-

Molecular Weight: 320.0 g/mol

Bioavailability after oral intake: about 40%

Distribution Sites: fatty tissues

Metabolism Sites: liver

Excretion: biliary and urinary

Half-life: 18-159 days

Steady state: one month

to the Cytochrome P450 family enzymes involvement, essentially an hydroxylation process, may happen at the a or at the ß-carbon molecule site, leading to the for- mation of o,p-‘DDE and p,p’-DDA, respec- tively. Prevalent line is the ß hydroxylation, with the formation of an acyl-chloride, that, reacting with water, leads to DDA, main mi- totane metabolite, highly urinary excreted because water-soluble. Hydroxylation on Ca site, less frequent because obstructed by the ortho Cl on drug benzenic ring, leads to the formation DDE, mitotane metabolite with stored lipophilicity.

It has been reported that these active metabolites can cause toxicity by oxygen activation with superoxide formation or by covalent binding to specific proteins.33 Mitotane affects steroidogenesis by in- hibiting the cytochrome cholesterol side chain cleaveage enzyme (P450scc) which converts cholesterol to pregnenolone.33 Mitotane also inhibits other cyt P450 de- pendent enzymes, such as 11-hydroxylase and 18-ß-hydroxylase, as well as P450 in- dependent enzymes, e.g. 3-ß hydroxyster- oid-dehydrogenase.34 However, the exact mechanism of action of mitotane is still not fully understood.

Mitotane historical background

Most of the early pharmacology studies of mitotane 35-37 were done in dogs, where degeneration of mitochondria was detect- ed as early as 12 hours after drug admin- istration. The atrophic changes were most prominent in the zona fasciculata and zona reticularis, and were associated with un- responsiveness to ACTH administration, whereas changes in the zona glomerulosa were relatively modest.38, 30 With prolonged drug treatment, most of the cells of the zona fasciculata and zona reticularis were destroyed. Dogs treated with mitotane for 2 days showed a diminished cortisol secre- tion.39 Following the demonstration of the adrenotoxic effect in dogs, mitotane was used in humans in the late 1950s. In 1960, Bergenstal et al.40 reported significant tu-

Figure 1 .- Mitotane structure (o,p'-DDD).

tane pure powder must be stored in airtight containers, protected from light.31 Related to the pharmacokinetics of the compound, up to 40% of a mitotane dose is absorbed from the gastrointestinal tract; absorption increases with food and there is a signifi- cant distribution of mitotane and its me- tabolites in fatty tissue (Table I). After daily doses of 5 to 15 g, concentrations in the blood of 7 to 90 mg/L of unchanged drug and 29 to 54 mg/L of metabolites have been reported. Mitotane has been detected in the blood up to 6-9 weeks after stopping treat- ment; it is mainly metabolized in the liver and its metabolites are excreted in urine and bile. The elimination half-life of the parent compounds ranges between 18 and 159 days.31 Patients treated for several years may take many months to clear mitotane from the circulation.32 Therapeutic activity of mitotane depends on the transformation of the drug in its two active metabolites, o,p-‘DDE and p,p’-DDA; this process, due

TABLE I .- Mitotane: summary of characteristics.

Mitotane (o,p’-DDD)

Chemical Name: (1,1-dichloro-2-(2-chlorophenyl)-2-(4- chlorophenyl)ethane)

Molecular Formula: C14H10Cl4

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mor regression and reduced corticosteroid secretion in 7 of 18 ACC patients treated with o,p’-DDD. In 1966, Hutter and Kayhoe 41 observed reduced steroid levels and im- provement of symptoms (pain, weakness, anorexia) in about half of the patients con- sidered. Of 59 patients with measurable disease, in fact, 20 (34%) showed objective tumor regression of a median duration of 7 months at a daily mitotane dose of 8-10 g. During the early 1970s, Lubitz et al.42 in 1973 investigated 115 patients with inoper- able ACC using increasing doses of mito- tane until side effects occurred. Most pa- tients were treated with 5 to 10 g daily but the maintenance dose varied greatly (0.5- 20 g daily). Of 75 patients with measurable disease, 46 (61%) showed tumor regression and the survival in this series of mitotane treated patients was twice as high as report- ed in historical controls. In the same period, Hoffman et al.43 in 1972 reported a series of 19 patients who were given mitotane at variable doses (1-10 g daily) for a period ranging from 15 weeks to 19 months, but observed a much less convincing antiprolif- erative effects accompanied by substantial toxicity. These reports concluded that treat- ment with mitotane is absolutely justified in unoperable patients and in the event of severe steroid hypersecretion. The enthusi- asm for mitotane peaked during the mid- 1980s, when Boven et al.44 reported a pa- tient with a histologically proven complete response and identified 7 similar cases in the literature. Subsequent experience was less encouraging. Most reports described a partial and transient response only in a small proportion of the patients. In 1993, in an extensive review of the previous Eng- lish literature, Wooten and King 18 analyzed more than 500 patients who received o,p’- DDD and found that 35% of them showed a response, which was most often partial and transient.

In summary, mitotane has been widely employed for medical treatment of ad- vanced ACC for more than 40 years, but it is difficult to critically appraise the evidence of its efficacy, due to several limits of the published reports, particularly early studies,

performed before the era of modern imag- ing techniques. In such studies, assessment of tumor response was not done using standard criteria,45 and in some reports the only marker of response was the decrease of steroid levels.

Mitotane in advanced ACC

Mitotane was used in advanced ACC as a monotherapy and also in combination with other cytotoxic agents. A meaningful com- parison of the results of these studies is not readily feasible because of the variability in the criteria used to assess response.18, 46 Since in some studies hormonal ameliora- tion was used as a surrogate for response, it has been difficult to document a survival advantage in some series reporting a high percentage of remission.9, 46 Another con- founding factor is the fact that most studies were retrospective and employed variable dosages of mitotane, ranging from 3 to 20 grams daily using two different formula- tions: Lysodren (o,p’-DDD alone) and the so called “French mitotane” (o,p’-DDD mixed with enteric gastroresistant coated granules of cellulose acetylpthalate), respectively.

Studies published before the 1980s showed a considerable efficacy of mito- tane in controlling hormone hypersecre- tion (response rate, 73-85% of treated pa- tients), while the effect on tumor mass was less evident (34-61% of complete or partial remissions)42,28,48,49,41,43,50,51. In more recent studies a limited antineoplastic activity was attributed to mitotane, with a rate of objec- tive remissions of only 20-24%,15, 26, 28, 24, 48, 52, 53 moreover, these responses were usual- ly short-lasting. 15, 26, 34, 39, 52, 54, 26 Williamson et al.55 in 2000 used mitotane prospectively as a second-line treatment at disease pro- gression after treatment with cisplatin and etoposide, and the observed response rate was only 13%.

Haak et al.25 in 1994 reported a response rate of 27% in 55 patients with advanced ACC (complete remission in 8 patients and partial response in 7 patients with dura- tion of response of 2-190 months). Interest-

MITOTANE TREATMENT FOR ADRENOCORTICAL CARCINOMA

ingly, a tumor response was seen only in patients who showed high maintenance mi- totane serum levels; actually, the response rate was 55% among patients with elevated mitotane concentrations. This pivotal study introduced the concept of a therapeutic im- pact of mitotane concentrations after the preliminary observation by van Slooten et al.56 published in 1984, even if the thresh- old of 14 mg/L was established retrospec- tively and was not used for clinical decision making.

In a prospective study, Baudin et al.57 in 2001 included 13 patients with metastatic ACC showing an objective tumor response in 4 of them (31%). One response was com- plete and 3 were partial, lasting between 10 and 48 months. Also in this study the responses were observed only among the 6 patients who achieved plasma mitotane levels greater than 14 mg/L. In contrast, no response was observed among the 7 pa- tients with persistently low plasma mitotane concentrations. Interestingly, the authors reported that the 4 patients who initially responded to mitotane, had mitotane lev- els less than 14 mg/L at the time of disease progression. Thus, in the only two studies employing monitoring of serum mitotane concentration objective responses were ob- served only among patients whose serum mitotane concentrations were higher than 14 mg/L.35, 57 However, Seki et al.58 in 1999 have reported a patient who attained com- plete remission of a local recurrence and lung metastases although plasma mitotane levels were never above 10 mg/L.

Table II summarizes the outcome of mi- totane monotherapy in advanced ACC as it was reported in studies of more than 10 patients published in the English literature over the last 20 years. Notwithstanding the great heterogeneity of these studies, mito- tane appears to have some activity in induc- ing objective tumor regressions of variable duration (2-190 months); overall, the me- dian response rate was about 24% (range, 13-33%). Moreover, mitotane treatment was able to control hormone secretion in most patients with functioning ACC.46 Although a complete response in patients with ad- vanced ACC is infrequent and duration of response is extremely variable, long-term survival has been reported.59-86

Mitotane was associated with conven- tional cytotoxic agents in many series. The rationale for combining mitotane with clas- sic cytotoxic drugs is based on the finding that the drug is able to reverse the multid- rug resistance mediated by P-glycoprotein expression in vitro, thus enhancing the ef- fects of doxorubicin, vincristine and etopo- side.60, 61 However, such an effect could not be demonstrated in vivo.62

Mitotane plus chemotherapy

Multidrug resistance (MDR) is a major cause of chemotherapy failure in cancer treatment. Surveys of human tumors have found very high levels of multidrug resist- ance 1 (MDR1, ABCB1) expression in a ma- jority of ACC cases.63, 64 Susan Bates et al.60

TABLE II .- Outcome of mitotane monotherapy in advanced ACC.
Author, year; study type	Dose g/day	Patients Nº	Response N. (%)	Duration months
Venkatesh,1989; retrospective 28	NR	72	21 PRs (29)	NR
Luton, 1990; retrospective 15	3-20	37	5 PRs (13)	5-25
Decker, 1991; prospective 48	6	36	2 CRs, 6 PRs (22)	3-82
Pommier, 1992; retrospective 26	NA	29	PRs (24)	NR
Haak, 1994; retrospective 25	4-8	55	8 CRs, 7 PRs (27)	2-190
Barzon, 1997; retrospective 86	4-8	11	2 PRs (18)	40-64
Williamson, 1999; II line, prospective 55	4-10	16	PRs (13)	NR
Baudin, 2001; prospective 57	6-12	13	1 CR, 3 PRs (33)	10-48
		Tot. 269	Median 24%

NR: not reported; PR: partial remission; CR: complete remission; NA: not available

showed that mitotane in vitro can increase drug accumulation by decreasing drug ef- flux, resulting in enhanced cytotoxicity. This effect was observed was observed in cell lines expressing MDR1, suggesting that mitotane interferes with MDR1 function. Similar results have been obtained in a sub- sequent in vitro study.61 These observations provided the rationale of combining cyto- toxic therapy with mitotane.

The combination of mitotane with chem- otherapy has been tested in six phase II studies involving a total of 232 patients. In two studies single agents, cisplatin or strep- tozotocin, were tested, two studies em- ployed cisplatin containing regimens, while regimens without cisplatin were tested in the remaining two studies.

The activity of cisplatin plus mitotane was assessed in 42 patients with advanced ACC consecutively enrolled in a phase II trial of the SouthWest Oncology Group (SWOG) in the United States.65 These patients were divided in good-risk and poor-risk catego- ries, the former received cisplatin at 75 mg m2 while the latter 100 mg/m2. Thirty-seven patients were fully assessable while 5 were judged as ineligible. Six patients had been previously treated with mitotane, 2 with chemotherapy not containing cisplatin. Ob- jective responses were reported in 11 of 37 eligible patients (1 complete and 10 partial responses) for an overall response rate of 30% when considering evaluable and 26% according to the intent to treat analysis. Two of 11 responding patients had previ- ously received mitotane therapy. Median duration of disease response was 8 months (range 1-36).

In a Swedish experience, the combina- tion of streptozotocin plus mitotane was tested in 23 advanced ACC patients, 11 of them were previously radically operated patients who received this treatment only when local recurrences or metastases had developed, while the remaining 12 patients were in advanced stage in which surgery could not be curative.66 Seven of these pa- tients attained a disease response, one com- plete and and 6 partial responses lasting 7 months on average. Four of these patients

underwent radical surgery leading to long- term disease-free intervals and one of them was disease-free for 36 months and the re- maining 3 were disease-free for 3, 10, and 18 years, respectively.

In a phase II study conducted at the In- stitut Gustave Roussy in Paris from 1993 to 1997,67 18 patients with progressive meta- static or residual ACC in whom complete surgical removal of the disease was not possible were treated with the combination of cisplatin, etoposide, and mitotane. All patients had progressive disease to previ- ous mitotane therapy, 6 of them attaining serum drug levels in the therapeutic range (>14 mg/L). A complete response was ob- served in the 3 cases lasting 26+, 15, and 11 months, respectively; a partial response was reported in 3 cases, lasting 9, 11, and 9+ months, for an overall response rate of 33%. Two further patients obtained a dis- ease stabilization lasting 12 and 8 months, for an overall clinical benefit of 44%.

The largest prospective study published to date is a multicenter Italian phase II study, which recruited 72 consecutive lo- cally advanced or metastatic ACC patients from 26 institutions in 10 years.68, 69 All pa- tients had never been treated with systemic therapy for advanced disease, 13 patients had previously received mitotane in adju- vant setting. Thirty-five patients in this se- ries (48%) attained an objective response (5 complete and 30 partial) lasting 18 months on average; 20 patients had a disease stabi- lization. A clinical benefit was therefore ob- tained in 78% of patients. Ten responding patients underwent radical surgery of resid- ual disease and became disease-free. In one of them non neoplastic cells were observed at residual histology.70 Patients attaining a disease-free status (complete or partial re- sponse followed by radical surgery) had significantly prolonged disease-free survival and overall survival than patients with par- tial response and no response.

In an interesting phase II trial conducted at the US National Cancer Institute,62 doxo- rubicin, vincristine, and etoposide, 3 natu- ral products that can be transported out of cells by MDR1, were administered in asso-

ciation with mitotane (MAVE scheme) in 36 ACC patients with recurrent or metastatic disease. Mitotane was administered aggres- sively, seeking to achieve a serum level of 10-15 mg/L.

Thirteen patients (36%) had been previ- ously submitted to chemotherapy and 12 patients (33%) had received mitotane thera- py without success. Surgery with radical in- tent was attempted in responding patients. An objective response was documented in 5 of 36 evaluable patients (14%) with one complete response (3%), 4 partial response (11%). In addition 3 minor responses were obtained leading to a clinical benefit ob- tained in 8 patients (8%). The men dura- tion of response exceeded 12.4 months. Of the responding patients, 4 went on to have surgical resections performed and were radically operated. Although the overall re- sponse rate was not high, patients who re- sponded to therapy appeared to benefit a lot from the treatment regimen, since their overall survival after response was signifi- cantly higher than that of non- responders.

Tariquidar is a potent, specific, non- competitive inhibitor of MDR1 that inhib- its the ATPase activity of MDR1, In clinical trials, tariquidar is tolerable and does not have significant pharmacokinetic interac- tion with chemotherapy.71 The activity of the addition of tariquidar to the MAVE scheme was tested at the National Cancer Institute in the United States.72 Forty-six pa- tients with advanced ACC were enrolled. The overall response rate was modest, 9%, but complete responses were durable (>3 years). By contrast this scheme achieved a high rate of disease stabilization lead- ing to a clinical benefit obtained in 66% of patients. Six patients underwent radical surgery of residual disease and eventually became disease-free. In these patients the in vivo MDR1 inhibition was tested using a surrogate assay that employs rhodamine accumulation in circulating CD56 positive cells and by [99mTc]-sestamibi scan. [99mTc]- sestamibi scans demonstrated inhibition of functional MDR1 with a median increase accumulation of [99mTc]-sestamibi of 133% (range 10-240%) and 179% (range 38-424%)

in metastatic ACC lesions and normal liver, respectively. Rhodamine efflux from CD56+ cells was blocked with a median inhibition of 92% at 24h and 81% at 48h, demonstrat- ing excellent MDR1 inhibition in vivo.

The low response rate obtained in this study despite the activity of tariquidar plus mitotane in inhibiting the MDR1 efflux pump suggests that MDR1 inhibition has only a limited effect in improving the chem- otherapy efficacy. MDR1 gene expression, therefore, is only one of the mechanisms involved in the chemotherapy resistance of ACC. Further efforts are needed to explain mechanisms of chemotherapy sensitivity and resistance of this disease. On the other hand, the proportion of patients attaining a stable disease in this trial was notewor- thy. Even though disease stabilization might be a consequence of an indolent disease course in some cases, it remains plausible that the beneficial aspects are attributable to treatment efficacy in other cases.

The MAVE tested at the NCI in 2 subse- quent studies led to an overall response rate that seems to be much lower than that obtained with cisplatin-containing regi- mens. These data suggest that cisplatin is a reference drug for ACC and should be included in the combination regimens em- ployed in the management of this disease. Taken together the overall cumulative activ- ity of chemotherapy plus mitotane schemes seems to be higher than that obtained with chemotherapy without mitotane. Responses obtained can be longlasting particularly if surgery of residual disease is performed.

Mitotane toxicity and dosage

The toxicity of mitotane and the fact that it appears to have only a narrow therapeu- tic range have been major hurdles for its clinical application.26, 47 Limited studies have correlated mitotane activity and toxicity with drug blood concentration 25, 57 show- ing that the most severe adverse effects be- come manifest for blood levels greater than 20 mg/L, while disease response is mainly confined to patients achieving blood lev-

els greater than 14 mg/L).25, 57 Although the threshold mitotane concentration of 14 mg/L was defined arbitrarily and retrospec- tively by van Slooten et al.56 in 1984, the therapeutic impact of such concentrations has been confirmed in a further prospective study by Baudin et al.57

The optimal mitotane schedule still re- mains matter of controversy. High mitotane doses may achieve the therapeutic range rapidly at the price of a substantial toxic- ity.57, 73 Low doses are better tolerated but usually achieve the therapeutic range after some months and this time lag may pose a problem when treating patients with a rapidly progressive disease.74 It is actually not clear how many patients are able to attain and maintain consistently over time mitotane levels in the therapeutic range. In a French experience, using the so called “French mitotane”, elevated concentrations were reached in about 50% of patients,57 while in an Italian series 100% of the pa- tients who were given Lysodren reached the therapeutic levels after 3-5 months.74 Both experiences, however, are too small for any generalization of these results.

It has been observed that exists a differ- ence on drug dosage administered between sex. In order to maintain on average the same mitotane plasma level men need more drug compared to women. Realistically it can be related to the different hormonal pattern existing and to the different amount of fatty tissue between genders.75

The most common unwanted effects are gastrointestinal manifestations (nausea, vomiting, diarrhea, anorexia) that occur early in the course of treatment and are par- tially independent from mitotane levels.73, 76 Interestingly, gastrointestinal symptoms are particularly evident at any increment in mitotane dose. However, well-informed and motivated patients are able to cope with side effects without discontinuing per- manently mitotane proven that expert care and careful counseling are provided.59, 76 The application of temporary dose reduc- tion or discontinuation is useful because patients may gradually develop tolerance to the unwanted effects of mitotane and then

be able to resume treatment and to attain elevated drug levels without new episodes of toxicity.30, 76 Typical adverse effects due to mitotane administration include elevation of liver enzymes and neurological toxicity (depression, lethargy, somnolence, ataxia, dizziness, confusion, vertigo). Almost uni- versal is the elevation of GGT and alkaline phosphatase that, however, rarely assumes clinical relevance.76 However, severe hepa- totoxicity has also been described.59 Neuro- logic effects of mitotane seem to be related to the plasma levels of the drug, and rarely occur when plasma o,p’-DDD is below 20 mg/L. These manifestations are always tran- sient and disappear after the drug is discon- tinued for several days.

Theoretically every patient on chronic mitotane treatment will develop adrenal insufficiency (if ACC is non-functional or mitotane is given in an adjuvant setting), re- quiring an high dose glucocorticoid replace- ment due to increased metabolic clearance of glucocorticoids and remarkable induc- tion of cortisol binding globulin, leading to impaired bioavailability of free cortisol.59, 76, 77 Inadequately treated adrenal insufficiency enhances mitotane induced side-effects and reduces tolerance.78 Conversely, mineralo- corticoid supplementation is not mandatory in all patients because aldosterone produc- tion is relatively spared. Hypogonadism and gynecomastia may develop in the long term needing testosterone replacement in some patients, because testicular steroidogenesis is also affected by mitotane whereas syn- thesis of sex hormone binding globulin is increased and this reduces free testosterone concentration.76 In some patients, also free thyroid hormone concentrations decrease and thyroxin replacement may become necessary.59, 76 The weak estrogen-like ac- tion of mitotane may contribute to sexual dysfunction in men while women are less affected.79 Leukopenia, prolonged bleeding times, increase in cholesterol and triglycer- ides may also occur.59

In this context, the monitoring of circu- lating mitotane levels may be useful to tai- lor individually the therapy and limit side- effects thus attaining better compliance to

treatment. Therapeutic mitotane monitoring may be useful, too, in case of co-adminis- tration of interfering drugs, leading to the discovering of useless treatment.

The implementation of blood mitotane monitoring, through a service provided by the company distributing Lysodren in Europe (Lysosafe, www.lysodren-europe.com), has rendered the use of this drug more feasible in the clinical practice because it is possible to anticipate and prevent toxicity. Our cur- rent experience with a monitored mitotane regimen is very promising so that it may be argued that measurement of circulating mitotane concentration has become manda- tory for a proper management of patients with ACC.

A recent paper by Hermsen and col- legues80 has reported, furthermore, that also mitotane metabolites plasma levels (espe- cially DDA) may be relevant as predictors of tumor response in ACC patients. Another evidence of importance of performing ther- apeutic drug monitoring in patients.

Mitotane in adjuvant setting

Since ACC has a high propensity to re- cur even after apparent complete resec- tion, many investigators have considered the use of adjuvant therapy. Mitotane has been widely employed with this aim81,9,47 but its efficacy remains a matter of debate. In fact, the literature reported conflicting re- sults that may likely be explained by several reasons.

Le copie e si el

First, most studies had a limited statisti- cal power: as a matter of fact, only three studies included series of more than 20 pa- tients.54, 78, 82, 83 In the study of Luton et al.,15 23 patients received mitotane after appar- ently curative surgery. However, the results of mitotane treatment in such patients were analyzed together with results in advanced disease, thus preventing a specific evalua- tion of the efficacy of adjuvant mitotane.

Second, some studies did not include a concomitant control group of untreated pa- tients with comparable baseline characteris- tics.28, 78, 82-85

Third, in some series, a number of pa- tients underwent multiple adjuvant treat- ments, thus it is difficult to appraise the specific effect of mitotane.26, 82

Fourth, all studies but one 57 were retro- spective and have employed variable doses of mitotane, ranging from 3 to 20 grams dai- ly, that were given for variable time periods. Table III reports the outcome of adjuvant mitotane treatment in the published studies.

Schteingart et al.85 were the first in 1982 to suggest that an adjunctive low-dose mi- totane regimen was beneficial immediately after tumor resection in a small uncon- trolled study. Additional data supporting the efficacy of adjuvant mitotane were pro- vided by Venkatesh et al.,28 who reported that 6 out of 7 patients on adjuvant mito- tane were alive one to 4 years after surgery, and by Dickstein et al.,84 who reported that a low-dose mitotane treatment started soon after surgical removal of ACC had a positive influence on survival in 4 patients. Further- more, Kasperlik-Zaluska et al.78, 83 reported that 18 out of 32 patients treated with mi- totane immediately after surgery were alive at the last follow-up as compared to 6 out of 27 patients who had started treatment 2 to 15 months after surgery, versus one out of 8 untreated patients. However, a formal survival analysis was not performed and precise data on the proportion of patients who underwent complete resection were not reported.

On the other hand, Bodie et al.54 in 1989 did not demonstrate any difference in the overall survival between patients with lo- calized disease treated with surgery alone or with surgery followed by adjuvant mito- tane. Nevertheless, the authors argued that selected patients appeared to have some beneficial effects from adjuvant mitotane. Pommier and Brennan 26 did not observe any positive effects of adjuvant mitotane on disease free survival as compared with un- treated patients. Vassilopoulou-Sellin et al.46 did not observe any significant difference in the survival of 8 patients who received adjuvant mitotane treatment and 6 patients who received no postoperative treatment. However, 5 of the patients on adjuvant mi-

TABLE III .- Outcome of adjuvant mitotane treatment.
Author, year	Treatment groups	Dose g/day	Patients Nº	RFS	Notes
Schteingart, 1982 85	Mitotane	6	4	NR	Survival was 74 ± 33 Ms
Venkatesh, 1989 28	- Mitotane -	NR	7	NR	6/7 pts were alive at last FU
Bodie, 1989 54	Mitotane	NR	21	NR	No difference between groups
Bodie, 1989 54	Control		25
Pommier, 1992 26	Mitotane	NR	10	2.4 Ys vs 2.5 Ys	RT was also used in 3 pts
Pommier, 1992 26	Control		43
Vassilopoulou-Sellin, 1993 46	Mitotane	4-6	8	10 Ms vs 23 Ms	Treatment was discontinued early for
Vassilopoulou-Sellin, 1993 46	Control		6		toxicity in 5 pts
Haak, 1994 25	Mitotane	4-8	11	NR	Survival was 51 vs 61 Ms; no impact
Haak, 1994 25	Control		15		of MIT levels on relapse
Barzon, 1997 86	Mitotane	4-8	7	8 Ms vs 13 Ms	71% pts in the MIT group are NED vs
Barzon, 1997 86	Control		11		27% of controls
Kasperlik-Zaluska, 2000 78	Mitotane	4-5	55	18-68 Ms	At the last FU, 56% of pts treated
	-		-		earlier are alive vs 22% of pts treated later and 12% of untreated pts
	-
Icard, 2001 82	Mitotane -	3-8	83	NR	MIT had no independent effect on
Icard, 2001 82	Mitotane -		-		survival
Baudin, 2001 57	Mitotane	6-12	11	72% of pts recurred	No impact of MIT levels on relapse
Baudin, 2001 57	-		-	in 1 Y
Terzolo, 2007 87	Mitotane	1-5	47	42 Ms in the MIT	MIT had an independent effect on
	Control		55	group vs 10 and	survival (p<0.001)
	Control		75	25 Ms in control
				groups
Dickstein, 2007 84	Mitotane	1.5-3	14	NR	5-Ys survival 75%
Bertherat, 2007 88	- Mitotane	NR	- 86 80	No difference	Trend for benefit of MIT in cortisol-
Bertherat, 2007 88	Control		- 86 80	between groups	secreting ACCs
RFS: recurrence free survival; NR: not reported; M(s): month(s); pts: patients; FU: follow-up; Y(s): year(s); RT: radiotherapy; MIT: mitotane; NED: no evidence of disease; ACCs: adrenocortical cancer.

totane discontinued the drug early because of toxicity. In the report of Barzon et al.,86 the 7 patients treated with adjuvant mito- tane showed a median disease-free survival of 8 months compared to 13 months in 11 untreated patients. However, 5 of 7 patients in the mitotane group are without any evi- dence of disease at the last follow up, in contrast to 3 out of 11 patients in the con- trol group.

Further evidence of the ineffectiveness of adjuvant mitotane came from the French multicentric study of Icard et al.,13, 82 who did not observe that mitotane had an in- dependent effect on survival after appar- ent curative surgery in multivariate analysis. However, it was not reported whether the patients treated with mitotane had prognos- tic factors comparable to those of the un-

treated patients. Haak et al.25 demonstrated in 1994 that mitotane was ineffective as ad- juvant therapy in 11 patients, and also in the experience of Baudin et al. 57 mitotane did not significantly influence disease-free recurrence and relapse rate in 8 out of 11 patients within 1 year. These two groups 25, 57 employed the monitoring of serum mito- tane concentrations but they did not find any association between elevated mitotane concentrations and outcome in an adjuvant setting.

Given its recognized toxicity and the lack of a clear evidence of efficacy, mitotane use as an adjunctive treatment had declined in recent years, and no recommendation re- garding adjuvant treatment was made at a 2003 consensus conference on ACC held in Ann Arbor, MI, USA.29

More recently, the results of a retrospec- tive analysis involving a large cohort of patients with ACC, who were followed for up to 10 years at different institutions in Italy and Germany, have been published.87 Adjuvant mitotane treatment was admin- istered to 47 Italian patients after radical surgery, and recurrence-free survival in these patients (the primary outcome of the study) was compared with that of two independent groups of 55 Italian and 75 German patients whose surgery was not followed by mitotane. Recurrence-free sur- vival was significantly prolonged in the mitotane group, as compared with the two groups of untreated patients (median recurrence-free survival, 42 months versus 10 months in the Italian control group and 25 months in the German control group). The patients who were left untreated af- ter radical resection of ACC had a signifi- cantly higher risk of recurrence than those receiving mitotane. Although the study was retrospective, the mitotane group and the Italian control group were highly compa- rable for the clinical characteristics known to affect outcome, while the control group from Germany had even better prognos- tic factors making mitotane effects more impressive. Indeed, multivariate analysis confirmed that mitotane treatment resulted in a significant advantage for recurrence- free survival. Similarly, overall survival ap- peared to be longer in patients receiving adjuvant mitotane, even if the difference between the mitotane group and untreated patients was less apparent.

The two major advantages of this study compared to previous ones are the large series and the fact that mitotane was given adjuvantly to all patients in some centers while in other centers no treatment was recommended according to a predefined protocol and not on the basis of selected patient or tumor characteristics. Thus, the study included concomitant cohorts of patients with similar baseline characteris- tics and statistical analysis was intention- to-treat. Moreover, similar work-up pro- tocols were used at the different centers and almost all histological diagnoses were

reviewed centrally. We cannot completely exclude the possibility of an unknown fac- tor that may have contributed to the better outcome of the mitotane-treated patients; however, the study appears free of major biases, as long as this can be true for a retrospective study. Another important finding is that favorable outcomes were achieved with low doses of mitotane (1 to 5 g per day) thus explaining why treatment was associated with acceptable adverse event rates.87 However, it may be argued that side effects have been likely underes- timated due to the retrospective nature of the study. Conversely, severe and disabling toxicity was observed in the studies where high, rapidly increasing, daily doses of mi- totane were employed.26, 46

In contrast to this experience, Bertherat et al.88 found that adjuvant mitotane was inef- fective in a cohort of 166 patients who un- derwent complete tumor removal. In their series, mitotane use was not associated with any improvement in disease-free survival; however, they found a tendency for ben- efit of adjuvant mitotane in patients with cortisol-secreting ACCs. Bertherat et al.88 raised the question whether the efficacy of mitotane may be influenced by the secre- tory activity of ACC. It is biologically plausi- ble that hypercortisolism may portend to an unfavorable prognosis in patients with ad- vanced ACC as previously reported by the same group;19 in disease-free patients, how- ever, its anti-secretory activity may be less a factor to determine outcome. It has to be said that since mitotane was administered to only half of the patients in this cohort, treated patients may have been selected for unfavorable prognostic factors.

In practice, after ACC is completely re- moved, physicians should solve the dilem- ma of instituting adjuvant therapy or simply follow patients without initiating treatment. Schteingart 89 in 2007 concluded that the study of Terzolo et al.87 provided a com- pelling rationale for the use of low-dose mitotane as adjuvant therapy in patients presenting with stages I to III ACC whose surgical resection has been macroscopically complete;89 however, controversy concern-

ing mitotane as adjuvant therapy may con- tinue.87, 90

Many areas of controversy remain con- cerning adjunctive mitotane therapy be- yond the issue of efficacy that should be solved only by prospective studies.

First, which is the optimal dose regimen? At some centers the use of a low-dose regi- men appears to be better tolerated. How- ever, even if all patients are able to attain elevated mitotane concentrations the time needed to enter the therapeutic levels is very long. This is in contrast to the rationale of an adjuvant therapy, meaning institution of treatment as close to surgery as possible. Conversely, a high-dose regimen is able to provide elevated concentration more rap- idly, but is fraud with increased side ef- fects.73 A solution to this dilemma may be the initiation of therapy before surgery with a loading dose and to proceed with main- tenance doses as soon as therapeutic levels are achieved.

Second, which is the optimal duration of therapy? The time to first recurrence after complete tumor resection is highly vari- able ranging from a few months to more than ten years, but most recurrences occur within 2 years after primary surgery.9, 26, 46, 81, 91 In the multicenter series collected by Terzolo et al.,87 about 70% of relapses took place in the first 2 years of follow-up, while the frequency of late (>5 year) relapses was less than 1%. The currently best approach to this dilemma is to discuss risks and ben- efits of mitotane therapy with the patient. The clinician can then accommodate pa- tient preferences between a range of possi- bilities (2, 5 or even more years of therapy) in a shared decision-making depending on tumor and patient characteristics.

In conclusion, there is evidence that adju- vant mitotane treatment may benefit a part of patients with ACC, even if the retrospec- tive nature of the recent study warrants cau- tion in the interpretation of the results.57 A better understanding of which factors can influence prognosis and response to treat- ment will help stratifying patients according to their risk of relapse, with the aim to iden- tify subgroups of patient for whom the ben-

efits of adjunctive mitotane are maximal. The only way to answer the open questions is performing randomized trials. Therefore, a trial for patients at low-intermediate risk of recurrence who are randomized to mito- tane versus observation only (ADIUVO trial, http://www.epiclin.cpo.it/adiuvo) has been initiated under the endorsement of the Eu- ropean Network for the Study of Adrenal Tumors. However, until results from this and other randomized trials are available, clinicians have to deal with the uncertain- ty. In the meantime clinical judgement and personal experience will be the main ba- sis for decision-making regarding mitotane treatment of patients with ACC.

Riassunto

Trattamento con mititane nel carcinoma cortico- surrenalico: una panoramica

il carcinoma corticosurrenalico (CCS) è una ne- oplasia endocrina rara altamente aggressiva, carat- terizzata da prognosi spesso sfavorevole e da una sopravvivenza inferiore a 5 anni nel 50% dei casi. Spesso evidenziato per via incidentale, la diagnosi di CCS viene effettuata nella maggior parte dei pa- zienti ad uno stadio avanzato di malattia, quando già, cioè, può presentarsi unampia invasione del tumore primario negli organi adiacenti. La rimozio- ne chirurgica completa della neoplasia è, oggi, il trattamento di prima scelta per il CCS: margini di resezione liberi da malattia, infatti, hanno un forte valore predittivo di migliore sopravvivenza a lungo termine. La maggior parte dei pazienti sottoposti ad intervento, tuttavia, è destinata a recidivare, eviden- za che induce albimpiego di una terapia farmacolo- gica. Il farmaco delezione nel trattamento del CCS, è il mitotane (o,p-DDD), farmaco con azione adre- nolitica, associato o meno ad altri chemioterapici. Tale terapia è indicata nei pazienti con malattia ino- perabile e, sebbene bevidenza clinica ancora non esista, anche post-intervento con intento adiuvante. Sebbene tale farmaco sia impiegato da anni, la rari- tà della patologia e la tossicità del mitotane hanno precluso borganizzazione di trials clinici di tipo ran- domizzato. Il ruolo del mitotane nel trattamento dei pazienti affetti da CCS, resta ad oggi, ancora, su più fronti, non completamente chiarito.

Obiettivo di tale articolo, dunque, è di rivedere le conoscenze attuali sul mitotane sia somministrato in pazienti con malattia inoperabile sia somministrato con intento adiuvante in fase post-operatoria.

Parole chiave: Ghiandole endocrine, tumori - Carci- noma Adrenocorticale - Mitotane, tossicità.

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Received on November 16, 2011. Accepted for publication on January 27, 2012.

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