Everolimus therapy for progressive adrenocortical cancer
M. Fraenkel . M. Gueorguiev . D. Barak . A. Salmon . A. B. Grossman . D. J. Gross
Received: 7 November 2012/ Accepted: 7 January 2013/Published online: 16 February 2013 @ Springer Science+Business Media New York 2013
Abstract Patients with advanced adrenocortical carci- noma (ACC) have limited treatment options after failure of chemotherapy. Tumor IGF2 expression has been shown to be amplified in the majority of cases of ACC and autocrine/ paracrine activation of the IGF receptor (IGF-R) is thought to play a major role in the pathogenesis of ACC. It has been shown in vitro that inhibition of the IGF-R inhibits ACC cell proliferation. mTOR is a downstream effector of the IGFR signaling pathway; therefore, the rapamycin analog everolimus could prove to be useful for treatment of patients with ACC. Four women with ACC (ages 25-60 years) developed stage IV disease after surgery. All had progressive disease (PD) despite treatment with
M. Fraenkel and M. Gueorguiev-joint first authors.
M. Fraenkel · D. Barak · D. J. Gross Neuroendocrine Tumour Unit, Endocrinology & Metabolism Service, Department of Medicine, Hadassah-Hebrew-University Medical Center, Jerusalem, Israel
M. Gueorguiev
Department of Endocrinology, St Bartholomew’s Hospital, Queen Mary University of London, London, UK
M. Gueorguiev ☒ · A. B. Grossman
Centre for Endocrinology, William Harvey Research Institute, Barts and the London School of Medicine, Queen Mary University of London, Charterhouse Square, London EC1M 6BQ, UK
e-mail: m.gueorguiev@qmul.ac.uk
A. Salmon
Sharett Institute of Oncology, Hadassah-Hebrew-University Medical Center, Jerusalem, Israel
A. B. Grossman
Oxford Centre for Diabetes, Endocrinology and Metabolism, Churchill Hospital, University of Oxford, Oxford, UK
mitotane and other treatment modalities (etoposide, doxo- rubicin, cis-platinum in 3/4 patients, further streptozoto- cin + 5-FU in 1/4 patients, further thalidomide therapy in 2/4 patients; 1 patient progressed on an IGF-R antagonist). The patients were started on everolimus 10 mg/day orally and 2/4 patients also continued mitotane. Disease pro- gression was monitored monthly by CT in 3/4 and after 3 months in 1/4. In all patients everolimus was well tol- erated. In the three patients monitored monthly, PD was evident after 1, 3, and 4 months; in the patient evaluated after 3 months PD was also evident. In this small explor- atory study, no clinically meaningful response was observed with everolimus in four patients with advanced ACC. The failure of efficacy could be related to an inter- action with mitotane, multiple signaling pathways, and/or other downstream IGF-R effectors operative in the patho- genesis of ACC.
Keywords Everolimus . Adrenocortical carcinoma . Tyrosine kinase inhibitors · Mitotane
Introduction
The large majority of patients with adrenocortical cancer, a rare malignancy, have a very poor outcome [1]. Survival is limited to 38 % at 5 years and is less than 12 months for unresectable tumors with distant metastases [2, 3]. Radical surgery can achieve cure for some patients with localized disease, but the recurrence rate remains high [1]. Adjuvant therapy with mitotane prolongs recurrence-free survival in less than 23 % of patients [4], and it seems to have a place as a therapeutic approach even in patients with early stage disease after surgical excision [5]. The effect of medical therapy on survival is relatively limited. With disseminated
disease, stages III-IV, the prognosis is especially guarded: first-line chemotherapy with etoposide, doxorubicin, and cis-platinum combined with mitotane resulted in a 23.2 % response rate, but a clear cut benefit on survival has been difficult to confirm [6].
Several studies have documented evidence for involve- ment of both IGF-2/IGF-1R (insulin-like growth factor 1 receptor) and mTOR pathways in the pathogenesis of adrenocortical carcinoma (ACC) [7-10]. Inhibitors of both pathways cause inhibition of cell proliferation of human ACC cell lines in vitro, and of growth of tumor xenografts in vivo [7-9, 11]. These observations have supported the rationale for considering therapy with an mTOR inhibitor for our patients with ACC. We present some preliminary data on the use of an mTOR inhibitor.
Case reports
The patients’ clinical outcome and therapies are summa- rized in Table 1.
Patient 1 presented at age 57 with Cushing’s syndrome caused by a stage II ACC (ENSAT classification) [11] secreting cortisol. Adjuvant mitotane therapy was started immediately after laparoscopic resection of the tumor. Six months after surgery her disease progressed, she received systemic chemotherapy with etoposide, doxorubicin, and cis-platinum (EDP), and after failure of this protocol she further received chemotherapy with streptozotocin (STZ) plus 5-fluorouracil (5-FU),and then further thalidomide therapy (Table 1). She progressed despite this multi- modality approach and was commenced on treatment with the mTOR inhibitor everolimus (Afinitor®, Novartis), supplied by Novartis (Basel, Switzerland) as part of their compassionate use program. She continued mitotane treatment 2.5 g/day while taking everolimus, with a ther- apeutic mitotane blood level of 16 mg/L. Treatment with everolimus was well tolerated (Table 1). Disease status was monitored monthly by CT. However, she showed disease progression at 1 month and died while still receiving everolimus.
Patient 2 was a 58 year-old female who was discovered to harbor a 6 cm ACC which was removed laparoscopi- cally. Adjuvant mitotane was commenced 3 months after surgery. She underwent repeat surgery for progression to stage IV disease 18 months after initial surgery, followed by systemic chemotherapy with EDP and further thalido- mide therapy (Table 1). Therapy with everolimus was initiated at disease progression. The patient stopped mito- tane (2.5 g/day) at the initiation of everolimus treatment and the mitotane blood level was 7.12 mg/L at that time. The response to everolimus was assessed monthly with CT. Only low-grade adverse events were reported (Table 1).
After failure of everolimus (time to progression of 4 months), she received radiotherapy to vertebral metas- tases and systemic treatment with sunitinib: despite these interventions, her disease progressed and she died 5 months after discontinuation of everolimus.
Patient 3 was a 25 year-old female patient in whom 9 cm non-functional ACC was diagnosed and resected laparoscopically followed by adjuvant mitotane treatment 2 months later. She progressed to stage IV after 9 months of adjuvant mitotane and then received systemic chemo- therapy with etoposide, doxorubicin, and cis-platinum, which failed. In addition she received radiotherapy to a large metastasis adjacent to the liver (Table 1). She stop- ped mitotane (2 g/day) 1 month prior to everolimus treat- ment with blood levels of 18.7 mg/L. Upon evidence of disease progression (monthly CT monitoring) after 3 months of everolimus this treatment was stopped; she restarted treatment with mitotane (3-3.5 g/day) and in addition received four cycles of chemotherapy with gem- citabine and capecitabine. Gemcitabine was stopped due to toxicity and she continued capecitabine for another five cycles. The last five cycles were combined with bev- acizumab intravenously. Despite this treatment, she died 9 months after discontinuation of everolimus.
Patient 4 was a 60 year-old woman with an incidentally discovered right non-secretory ACC, stage I, during inves- tigations for a peptic ulcer. Laparoscopic resection of the tumor was performed with resection of a 9 cm mass. She received adjuvant mitotane therapy within 3 months of surgery, but she progressed within 4 months to stage IV. A solitary liver metastasis was treated with radiofrequency ablation. The patient refused chemotherapy and chose to enroll in a clinical trial with an IGF-receptor (IGF-1R) antagonist (OSI-906, OSI Pharmaceuticals Inc., Colorado USA), on which she progressed after 4 months of treatment. After further progression everolimus was started. Mitotane was stopped 8 months before initiation of everolimus (blood level of 4 mg/L after 5 months). The time to progression on everolimus was 3 months (assessed with CT scanning): there was an increase in size of a portocaval mass and of a mass at the right renal hilum, and the drug was then stopped. Treat- ment with everolimus was well tolerated (Table 1). She received further treatment with sorafenib (Nexavar®, Bayer) for 3 months, which failed to halt disease progression, and after treatment with intravenous zoledronate and one cycle of chemotherapy with lomustine and capecitabine, she died following acute pneumonia.
Discussion
Tremendous progress in the field of molecular targeted cancer therapies in the last few years has led to extended
| Patient identity | Age at diagnosis (years) | Tumor Weiss Mitotic diameter score Index at diagnosis and Ki67 (cm) | Stage at diagnosis (ENSAT or McFarlane) | Hormonal Adjuvant mitotane secretion | Mitotane levels under everolimus | |
|---|---|---|---|---|---|---|
| 1 | 57 | 11 5 10 % | II | Yes Cortsol | Yes | 15 mg/L M continued under everolimus |
| 2 | 58 | 6 6 8 per 50 HPF | IV | None Yes | 7.12 mg/L M stopped at initiation of everolimus | |
| 3 | 25 | 9 6 25-50 per 50 HPF | IV | None Yes | 18.7 mg/L M stopped 1 month prior everolimus | |
| 4 | 60 | 3.7 8 10 per 10 HPF in hot spots | I | None Yes | 4 mg/L M stopped 8 months prior everolimus | |
| Patient identity | Time to first progression after surgery (months) | Treatment prior to everolimus | ECOG performance status prior to everolimus (on a scale of 0- 5 from best to worst) | Time to progression on everolimus (months)* | PFS ratio ** | Everolimus adverse effects (CTCAE 3va) | Therapy upon progression on everolimus | Overall survival since diagnosis (months) |
|---|---|---|---|---|---|---|---|---|
| 1 | 6 | EDP + M × 5; 5-FU + STZ × 3 cycles; thalidomide for 1 month | 1-2 | 1 | 1 | None | None | 13 |
| 2 | 18 | Surgery for locoregional disease × 3; EDP × 3 cycles thalidomide for 1 month | 0-1 | 4 | 4 | G1 mouth ulcers; worsening of hyperlipidemia | Radiotherapy, Sunitinib | 42 |
| 3 | 11 | EDP × 3; radiotherapy | 1-2 | 3 | 1 | G1 rash | M + gemcitabine × 4, capecitabine × 9; bevacisumab × 5 | 33 |
| 4 | 4 | RFA; IGF-1R antagonist × 4 cycles | 0-1 | 3 | 0.75 | G1 lethargy and mouth ulcers | Sorafenib 3 months, biphosphonates iv; lomustine + capecitabine × 1 | 46 |
ENSAT European network for the study of adrenal tumors classification; CTCAE 3va Common terminology criteria for adverse events version 3; ECOG Eastern cooperative oncology group; EDP Etoposide, doxorubicine, cis-platinum; EDP + M Etoposide, doxorubin, cis-platinum + mitotane; 5-FU 5-fluorouracil; HPF High Power Fields; IGF-IR IGF-1 receptor; PFS Progression Free Survival; RFA radiofrequency ablation
* Progression determined by the local radiologist
** Progression free survival (PFS) ratio: PFS using an investigational therapy (period B) is compared with PFS for the most recent therapy on which the patient had just experienced progression (period A). For more details see Ref. [23]
progression free survival (PFS) and overall survival (OS) for some cancers. Several isolated cases of patients with advanced metastatic ACC have presented prolonged regression after anti-angiogenic therapy with sorafenib [12] or thalidomide [13], after ADH-1 (Exherin™M), a N-cad- herin inhibitor [14], or bisphosphonate therapy [15]. However, most of ACC still remain one of the rare cancers escaping control, and this unmet therapeutic need for ACC is well illustrated by our patients who ineluctably pro- gressed toward a fatal outcome despite several therapies.
Mitotane remains a crucial adjuvant therapy for advanced ACC. Therapeutic plasma mitotane levels (≥14 mg/L) have been associated with a higher objective response rate (55-66 %) in early studies [16, 17], with longer survival for patients with progressive disease [18, 19], and a trend toward increased overall survival [16].
This study reports on the use of everolimus in patients with progressive metastatic ACC. Everolimus has shown efficacy in treating other endocrine cancers (pancreatic neuroendocrine tumors, pNETs) [20], but surprisingly failed to lead to any therapeutic benefit in our patients. This is intriguing as two other small studies have reported some benefit of two mTOR inhibitors, sirolimus and temsiroli- mus, in ACC [21, 22]. Thus, stable disease was reported in 40 % (10 patients) while a partial response with prolonged survival (11 cycles/months) has been reported with com- binations of temsirolimus and cixutumumab (a fully human monoclonal antibody inhibiting IGF1R) [21], or sunitinib and sirolimus [22], respectively. The progression free survival (PFS) ratio has been speculated as a more valid and informative measure in assessing response to experi- mental treatments by Von Hoff et al. [23]. With this method, PFS using an investigational therapy (period B) is compared with PFS for the most recent therapy on which the patient had just experienced progression (period A). If the PFS of period B/PFS of period A ratio is ≥1.3, then the investigational therapy can be defined as showing benefit for the patient [23]. According to this criterion, only one of our patients showed benefit from everolimus therapy (Table 1).
Several factors may have potentially contributed to the resistance/failure to everolimus in our patients. Tyrosine kinase inhibitors (TKIs) are all oxidized to varying degrees by the microsomal liver enzyme cytochrome P450 (CYP3A4). Thus, both VEGFR inhibitors sunitinib and sorafenib are metabolized by this pathway, to a major extent for sunitinib and partially (up to 17 %) for sorafenib [24-27]. Inhibition of CYP3A4 does not have any major consequences on plasma concentrations of either drug, and, therefore, on their therapeutic efficacy, because of the limited bioavailability of sunitinb and the only partial metabolism of sorafenib [24-27]. Similarly, everolimus is also metabolized and inactivated by CYP3A4 [28].
CYP3A4 is strongly induced by mitotane, and this effect persists up to 1 year after interruption of mitotane treat- ment [29-31]. Thus, interactions between mTOR or tyro- sine kinase inhibitors and mitotane are common and should be expected [30]. The induction of CYP3A4 by mitotane may have caused sub-therapeutic levels of everolimus and may have compromised its therapeutic efficacy in our patients who were receiving concomitant mitotane or had interrupted it several months prior to everolimus therapy. The drug interaction induced by the combination of tar- geted molecular agents with adjuvant mitotane can poten- tially result in reduced therapeutic efficacy of these compounds in the treatment of ACC.
Thus, the therapeutic efficacy of tyrosine kinase inhib- itors (TKIs) and everolimus in advanced ACC probably should be evaluated prior to treatment with mitotane, and monitoring of the blood levels of the study drugs will be essential in assuring their putative effect. Considering these observations, we may extrapolate that the few clinical trials with TKIs (sorafenib bevacizumab, erlotinib) [32-34], which have shown poor responses in ACC may not truly reflect the activity of these drugs as sub-therapeutic levels were probably attained. Indeed, mitotane interference was recently documented: lower sunitinib and its bioactive metabolite SU12662 plasma levels and modest therapeutic effect in patients with advanced ACC [35].
In addition, it is possible that activation of multiple sig- naling pathways and/or other downstream IGF-R effectors may be operative in the pathogenesis of ACC, inducing resistance to mTOR inhibitors, which could at least in part explain the failure of efficacy of everolimus in our patients. In vitro studies have not only demonstrated the activation of the AKT pathway (stimulated additionaly by IGF1), but also the overactivation of the pro-growth pathway RAS/RAF/ MEK/ERK (leading to increased phosphorylation of ERK1/2), thus leading to resistance or escape to the inhibitory action of mTOR inhibitors on cell growth and survival [10]. In addi- tion, overactivation of the autocrine/paracrine IGF2/IGF1R loop observed in ACC cells could also cause a decreased sensitivity to mTOR inhibitors [10]. In this context, further studies with combination therapy of mTOR inhibitors with other TKIs simultaneously targeting several signaling pathways (e.g. IGF-1R or PI3 K/Akt signaling) that are up regulated by mTOR blockade [36] may offer more effective therapy for ACC [37].
The introduction of everolimus at a too late stage in the disease course could also potentially compromise the therapeutic response to this compound in our patients. Although they were all in a reasonably good clinical con- dition (ECOG 0-1, Table 1), they were at a stage IV and already heavily pretreated. Thus, based on our experience, everolimus did not show major clinical benefit when used as salvage therapy in late stage progressive ACC patients.
In conclusion, our 4 patients showed a lack of clear efficacy of the mTOR inhibitor everolimus in the treatment of late-stage ACC. It is unclear as to whether this lack of activity is due to an inherent inability of a single mTOR inhibitor to alter the course of this aggressive disease at a late stage, or whether it is secondary to increased metab- olism induced by mitotane, or the interference of multiple signaling pathways leading to therapeutic resistance. In either case, it is difficult to consider the use of this agent as mitotane has now become the initial recommended therapy in patients with ACC so the use of everolimus in the absence of preceding mitotane is difficult to envisage.
Acknowledgments We are grateful to Novartis for providing everolimus for compassionate use. This study did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.
Disclosure Professor Gross and Professor Grossman have served as consultants and on the Advisory Board for Novartis and have received research funding from Novartis for other studies. Dr. Fraenkel has provided expert testimony for Novartis.
Conflicts of interest All remaining authors have declared no con- flicts of interest.
References
1. M. Fassnacht, B. Allolio, Clinical management of adrenocortical carcinoma. Best Pract. Res. Clin. Endocrinol. Metab. 23, 273-289 (2009)
2. K.Y. Bilimoria, W.T. Shen, D. Elaraj et al., Adrenocortical car- cinoma in the United States: treatment utilization and prognostic factors. Cancer 113, 3130-3136 (2008)
3. E. Baudin, S. Leboulleux, A. Al Ghuzlan et al., Therapeutic management of advanced adrenocortical carcinoma: what do we know in 2011? Horm Cancer 2, 363-371 (2011)
4. M. Terzolo, A. Angeli, M. Fassnacht et al., Adjuvant mitotane treatment for adrenocortical carcinoma. N. Engl. J. Med. 356, 2372-2380 (2007)
5. M. Terzolo, A. Ardito, B. Zaggia et al., Management of adjuvant mitotane therapy following resection of adrenal cancer. Endo- crine 42, 521-525 (2012)
6. M. Fassnacht, M. Terzolo, B. Allolio et al., FIRM-ACT study group, combination chemotherapy in advanced adrenocortical carcinoma. N. Engl. J. Med. 366, 2189-2197 (2012)
7. M.Q. Almeida, M.C. Fragoso, C.F. Lotfi et al., Expression of insulin-like growth factor-II and its receptor in pediatric and adult adrenocortical tumours. J. Clin. Endocrinol. Metab. 93, 3524-3531 (2008)
8. F.M. Barlaskar, A.C. Spalding, J.H. Heaton et al., Preclinical targeting of the type I insulin-like growth factor receptor in adrenocortical carcinoma. J. Clin. Endocrinol. Metab. 94, 204-212 (2009)
9. M. Doghman, A. El Wakil, B. Cardinaud et al., Regulation of insulin-like growth factor-mammalian target of rapamycin sig- naling by microRNA in childhood adrenocortical tumours. Can- cer Res. 70, 4666-4675 (2011)
10. M.C. De Martino, P.M. van Koetsveld, R.A. Feelders et al., The role of mTOR inhibitors in the inhibition of growth and cortisol secretion in human adrenocortical carcinoma cells. Endocr. Relat. Cancer 19, 351-364 (2012)
11. B. Mariniello, A. Rosato, G. Zuccolotto et al., Combination of sorafenib and everolimus impacts therapeutically on adrenocor- tical tumour models. Endocr. Relat. Cancer 19, 527-539 (2012)
12. C. Butler, W.M. Butler, A.A. Rizvi, Sustained remission with the kinase inhibitor sorafenib in stage IV metastatic adrenocortical carcinoma. Endocr. Pract. 16, 441-445 (2010)
13. R. Chacón, G. Tossen, F.S. Loria, M. Chacón, CASE 2. Response in a patient with metastatic adrenal cortical carcinoma with tha- lidomide. J. Clin. Oncol. 23, 1579-1580 (2005)
14. N. Yarom, D. Stewart, L. Avruch, R. Malik, J. Wells, D.J. Jonker, ADH-1 in the treatment of metastatic adrenocortical carcinoma- case report. Anticancer Res. 31, 3921-3925 (2011)
15. P. Boudou-Rouquette, J. Alexandre, O. Soubrane et al., Antitu- moural effect of the bisphosphonate zolendronic acid against visceral metastases in an adrenocortical cancer patient. Ann. Oncol. 20, 1747 (2009)
16. E. Baudin, G. Pellegriti, M. Bonnay, A. Penfornis, A. Laplanche, G. Vassal, M. Schlumberger, Impact of monitoring plasma 1,1- dichlorodiphenildichloroethane (o, p’DDD) levels on the treat- ment of patients with adrenocortical carcinoma. Cancer 92, 1385-1392 (2001)
17. H.R. Haak, J. Hermans, C.J. van de Velde, E.G. Lentjes, B.M. Goslings, G.J. Fleuren, H.M. Krans, Optimal treatment of adre- nocortical carcinoma with mitotane: results in a consecutive series of 96 patients. Br. J. Cancer 69, 947-951 (1994)
18. I.G. Hermsen, M. Fassnacht, M. Terzolo et al., Plasma concen- trations of o, p’DDD, o, p’DDA, and o, p’DDE as predictors of tumour response to mitotane in adrenocortical carcinoma: results of a retrospective ENS@T Multicenter study. J. Clin. Endocrinol. Metab. 96, 1844-1856 (2011)
19. P. Malandrino, A. Al Ghuzlan, M. Castaing et al., Prognostic markers of survival after combined mitotane- and platinum-based chemotherapy in metastatic adrenocortical carcinoma. Endocr. Relat. Cancer 17, 797-807 (2010)
20. J.C. Yao, M.H. Shah, T. Ito et al., RAD001 in advanced neuro- endocrine tumours, third trial (RADIANT-3) study group. Ever- olimus for advanced pancreatic neuroendocrine tumours. N. Engl. J. Med. 364, 514-523 (2011)
21. A. Naing, R. Kurzrock, A. Burger et al., Phase I trial of cixutumumab combined with temsirolimus in patients with advanced cancer. Clin. Cancer Res. 17, 6052-6060 (2011)
22. T.C. Gangadhar, E.E. Cohen, K. Wu et al., Two drug interaction studies of sirolimus in combination with sorafenib or sunitinib in patients with advanced malignancies. Clin. Cancer Res. 17, 1956-1963 (2011)
23. D.D. Von Hoff, J.J. Stephenson Jr, P. Rosen et al., Pilot study using molecular profiling of patients’ tumors to find potential targets and select treatments for their refractory cancers. J. Clin. Oncol. 28, 4877-4883 (2010)
24. V.L. Goodman, E.P. Rock, R. Dagher et al., Approval summary: sunitinib for the treatment of imatinib refractory or intolerant gastrointestinal stromal tumours and advanced renal cell carci- noma. Clin. Cancer Res. 13, 1367-1373 (2007)
25. N.P. van Erp, H. Gelderblom, H.J. Guchelaar, Clinical pharma- cokinetics of tyrosine kinase inhibitors. Cancer Treat. Rev. 35, 692-706 (2009)
26. N.P. van Erp, S.D. Baker, A.S. Zandvliet et al., Marginal increase of sunitinib exposure by grapefruit juice. Cancer Chemother. Pharmacol. 67, 695-703 (2011)
27. C. Lathia, J. Lettieri, F. Cihon, M. Gallentine, M. Radtke, P. Sundaresan, Lack of effect of ketoconazole-mediated CYP3A
inhibition on sorafenib clinical pharmacokinetics. Cancer Che- mother. Pharmacol. 57, 685-692 (2006)
28. V.H. Mabasa, M.H. Ensom, The role of therapeutic monitoring of everolimus in solid organ transplantation. Therapeutic Drug Monitoring 27, 666-676 (2005)
29. N.P. van Erp, H.J. Guchelaar, B.A. Ploeger, J.A. Romijn, J. Hartigh, H. Gelderblom, Mitotane has a strong and a durable inducing effect on CYP3A4 activity. Eur. J. Endocrinol. 164, 621-626 (2011)
30. M. Kroiss, M. Quinkler, W.K. Lutz, B. Allolio, M. Fassnacht, Drug interactions with mitotane by induction of CYP3A4 metabolism in the clinical management of adrenocortical carci- noma. Clin. Endocrinol. (Oxf) 75, 585-591 (2011)
31. V. Chortis, O. Schneider, A.E. Taylor et al., Steroid profiling in adrenocortical carcinoma reveals mitotane as a strong inducer of CYP3A4 and inhibitor of 5{alpha}-reductase with major impli- cations for cortisol and androgen metabolism. Endocr. Rev. 32, P1-P620 (2011)
32. A. Berruti, P. Sperone, A. Ferrero et al., Phase II study of weekly paclitaxel and sorafenib as second/third-line therapy in patients
with adrenocortical carcinoma. Eur. J. Endocrinol. 166, 451-458 (2012)
33. S. Wortmann, M. Quinkler, C. Ritter et al., Bevacizumab plus capecitabine as a salvage therapy in advanced adrenocortical carcinoma. Eur. J. Endocrinol. 162, 349-356 (2010)
34. M. Quinkler, S. Hahner, S. Wortmann et al., Treatment of advanced adrenocortical carcinoma with erlotinib plus gemcita- bine. J. Clin. Endocrinol. Metab. 93, 2057-2062 (2008)
35. M. Kroiss, M. Quinkler, S. Johanssen et al., Sunitinib in refrac- tory adrenocortical carcinoma: a phase II, single-arm, open-label trial. J. Clin. Endocrinol. Metab. 97, 3495-3503 (2012)
36. K.E. O’Reilly, F. Rojo, Q.B. She et al., mTOR inhibition induces upstream receptor tyrosine kinase signaling and activates Akt. Cancer Res. 66, 1500-1508 (2006)
37. M. Mazzoletti, F. Bortolin, L. Brunelli et al., Combination of PI3 K/mTOR inhibitors: antitumour activity and molecular cor- relates. Cancer Res. 71, 4573-4584 (2011)