Role of 18F-FDG PET/CT in management of adrenocortical carcinoma: a comprehensive review of the literature

Purpose Adrenocortical carcinoma (ACC) is a rare malignancy of the adrenal cortex. Despite the rarity of ACC, highly aggressive nature of this malignancy highlights the importance of early diagnosis and timely initiation of treatment. Accurate pre-surgical diagnosis and staging are critical to distinguish ACC from benign adrenal adenomas and to evaluate distant metastatic disease. Imaging methods with high sensitivity and specificity are indispensable in this endeavor. F-18-fluorodeoxyglucose positron emission tomography/computed tomography (F-18-FDG PET/CT) plays an important complementary role to anatomical imaging in the initial diagnosis of ACC, staging, and response assessment to treatment. In this manuscript, we comprehensively review the literature on the role of F-18-FDG PET/CT and the complementary role it plays with regards to structural imaging modalities in various phases of management of ACC. Methods We searched the literature for related terms to "adrenal lesions", "adrenocortical carcinoma", and "F-18-FDG PET/CT" by mapping their Medical Subject Heading (MeSH) tree structure using the Public Library of Medicine's (PubMed) Automatic Term Mapping (ATM). Then, we used all categories to search the PubMed database and Web of Science (Clarivate Analytics) Core Collection from 1950 to February 2021. Results After excluding studies in languages other than English, our initial search resulted in 506 publications. Twenty-one articles discussing adrenal involvements with non-neoplastic nature such as tuberculosis and histoplasmosis were excluded resulting in a total of 485 studies, including 320 original research manuscripts, 82 review articles, 54 editorial materials, and 29 meeting abstracts. The selected number of manuscripts that are cited in this article reflect an in-depth review of the publications focused on the role of F-18-FDG PET/CT in management of ACC as established in the literature. Our results showed that F-18-FDG PET/CT could play an important role in primary diagnosis of adrenal lesions including ACC tumors. This imaging modality demonstrated higher sensitivity in identification of malignant tumors compared to non-enhanced CT. Moreover, this modality demonstrated added complementary value to anatomical imaging in identification of distant metastases and staging, assessment of local disease recurrence, and finally evaluation of locoregional response to systemic therapy in ACC patients. Conclusion F-18-FDG PET/CT could play an important complementary role to structural imaging in evaluation of ACC tumors. Prospective studies assessing the value of F-18-FDG PET/CT are encouraged to definitively assess the incremental benefit of functional imaging compared to structural imaging.