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Rev Esp Med Nucl Imagen Mol. 2021;xxx(xx):xxx-xxx

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Bilateral adrenal hypermetabolism with 18F-FDG PET/CT as an incidental finding in suspected recurrence of adrenocortical carcinoma*

Hipermetabolismo adrenal bilateral con 18F-FDG PET/TC como hallazgo casual en la sospecha de recurrencia de carcinoma adrenocortical

J. Márquez Fernández*, L.M. Mena Bares, E. Carmona Asenjo, F.R. Maza Muret, E. Moreno Ortega, J.A. Vallejo Casas

Unidad de Gestión Clínica de Medicina Nuclear, Instituto Maimónides de Investigación Biomédica de Córdoba (IMIBIC), Hospital Reina Sofía, Universidad de Córdoba, Córdoba, Spain

Bilateral adrenal hypermetabolism with F-18 FDG PET/CT as an incidental finding in suspected recurrence of adrenocorti- cal carcinoma. We report the case of a 60-year-old man with right adrenocortical carcinoma (Stage I, Ki67 5-10%), who under- went incomplete laparoscopic adrenalectomy. Three months after surgery, a F-18 FDG PET/CT study was performed without adrenal

involvement evidence (Fig. 1), although a slightly hypermetabolic pulmonary nodule was observed in the right lower lobe (RLL). The mentioned nodule, was treated with SBRT (5 fractions/12 Gy on five consecutive days). In addition, adjuvant treatment with mitotane was established. Five months later, mitotane treatment was sus- pended due to poor tolerance and it was decided to perform a new

Figure 1. F-18 PET/CT study from the skull base to proximal thigh was performed 60 min after intravenous (i.v.) administration of FDG (160 MBq). Axial fusion image of the thorax lung window (A). We observed the subcentimetric pulmonary nodule in the RLL (SUVmax 1.9). Axial and Coronal fusion images of abdomen soft tissue window (B)(C). Three months after surgery, the postsurgical changes in the right adrenal remnant was observed, without significant increase in glycidic metabolism.

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# Please cite this article as: Márquez Fernández J, Mena Bares LM, Carmona Asenjo E, Maza Muret FR, Moreno Ortega E, Vallejo Casas JA. Hipermetabolismo adrenal bilateral con 18F-FDG PET/TC como hallazgo casual en la sospecha de recurrencia de carcinoma adrenocortical. Rev Esp Med Nucl Imagen Mol. 2020. https://doi.org/10.1016/j.remn.2020.11.008

* Corresponding author. E-mail address: marquezfernandezjuan@gmail.com (J. Márquez Fernández).

Figure 2. F-18 FDG-PET/CT study from the skull base to proximal thigh was performed 53 min after i.v. administration of FDG (155 MBq) after 5 months with mitotane adjuvant treatment. Axial fusion image of the thorax lung window (A). We observed a hypermetabolic ground glass image (SUVmax 6.7) in the RLL, corresponding to the area treated by SBRT. Axial and Coronal fusion images of abdomen soft tissue window (B) (C). Significant glycidic metabolism increase is observed in bilateral adrenal tissue (right adrenal remnant with SUVmax 12.4 and left adrenal gland with SUVmax 13.9) without morphological changes in the glandular structure.

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Figure 3. F-18 FDG-PET/CT follow-up study, after 10 months suspension of mitotane treatment. Acquisition from the skull base to the proximal thigh was performed 63 min after i.v. administration of FDG (173 Mbq). Axial and Coronal fusion images of abdomen soft tissue window (A)(B). A glycidic metabolism normalization is observed in the adrenal tissue (right adrenal remnant with SUVmax 1.8 and left adrenal gland with SUVmax 1.6).

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F-18 FDG PET/CT study. The study showed a notable increased gly- cidic metabolism in the left adrenal as well as in the right adrenal remnant, with lack of anatomical alteration. This could be justified by mitotane treatment and less probably related with neoplastic disease (Fig. 2). Inflammatory changes in the right lung parenchyma were related to recent radiotherapy treatment. In the follow-up, a new F-18 FDG PET/CT study was performed 10 months after the previous one, and this time, no adrenal hypermetabolism was observed, confirming the suspected relationship with mitotane treatment (Fig. 3). Mitotane is a chemotherapy treatment adjuvant to surgery used in adrenocortical carcinoma, that improves patient survival. It has a cytotoxic and inhibitory effect on the adrenal cor- tex, because its accumulation in the fascicular and reticular layers causes mitochondrial damage, and therefore, it produces necro- sis. Nevertheless, the mechanism is not fully known. The response

rate to mitotane in some series reaches up to 36%. This treatment is more frequently used in secretory tumors, incomplete resections and in tumors with a Ki67 proliferation index > 10%. Its use requires a first dose followed by adequate control of serum levels because the adverse effects are dose-dependent, most of them related to gastrointestinal disorders.1 Patients treated with mitotane are also treated with high-dose corticosteroids to minimize early-onset adrenal insufficiency. The goal of treatment is to achieve therapeu- tic mitotane levels and ACTH levels in the normal range. Patients persist with a state of relative hypocortisolism despite high replace- ment therapy, generally due to relative high ACTH levels. Although cortisol secretion is inhibited, the adrenal cortical cell has a high avidity for F-18 FDG, his is probably related to ACTH stimulation.2 In some series, this increase in glycidic metabolism in the contralat- eral adrenal tissue has been reported in up to 29% of cases with

J. Márquez Fernández et al. / Rev Esp Med Nucl Imagen Mol. 2021;xxx(xx):xxx-xxx

metabolic normalization within subsequent 24 months. This shows a link to an effect of concurrent mitotane treatment and a possible functional endocrine compensation.3 This case is an example of the importance of considering the physiopathological processes in the differential diagnosis between neoplastic recurrence and possible reactive hypermetabolism due to adjuvant treatment.

References

1. Wong KK, Miller BS, Viglianti BL, et al. Molecular imaging in the management of adrenocortical cancer: a systematic review. Clin Nucl Med. 2016;41:e368-82, http://dx.doi.org/10.1097/RLU.0000000000001112.

2. Mpanaka I, Lyra VD, Kaltsas G, Chatziioannou SN. High (18)F-FDG uptake by the remaining adrenal gland four months after surgery and initiation of mitotane treatment in two patients with adrenocortical carcinoma. Hell J Nucl Med. 2011;14:168-72.

3. Leboulleux S, Deandreis D, Escourrou C, et al. Fluorodesoxyglucose uptake in the remaining adrenal glands during the follow-up of patients with adrenocortical carcinoma: do not consider it as malignancy. Eur J Endocrinol. 2011;164:89-94, http://dx.doi.org/10.1530/EJE-10-0666.