Abstract
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Objectives: Adrenal cortical carcinoma (ACC) is a rare malignancy and has a very poor prognosis. Radical surgery is the only effective treatment for primary as well as recurrent tumor. Accurate and early disease localization is essential. The role of F-18 FDG PET/CT is not clear for initial staging or post-operative restaging of patients with ACC. The aim of the study was to evaluate the diagnostic utility of F-18 FDG PET/CT for initial staging and restaging in ACC patients.
Methods: In this study, we retrospectively reviewed the data of ACC patients referred for F-18 FDG PET/CT. PET/CT reports were evaluated by two nuclear medicine physicians and abnormal FDG uptake on PET images was correlated with the corresponding CT images. The gold standard for primary disease was histopathology examination. In cases of recurrence, it was either histopathology examination or radiological assessment of target lesions on follow-up. Diagnostic performance of F-18 FDG PET/CT to correctly categorize target lesions was assessed. PET/CT results were compared with CI (conventional imaging with US, CECT or MR). The sensitivity, specificity, positive and negative predictive values (PPV, NPV) and accuracy of imaging modalities were calculated.
Results: In this retrospective analysis, we evaluated 64 F-18 FDG PET/CT studies done in 46 patients of ACC over a period of 2010-16. Mean age was 42.8 years (range 16-77 years) and 25 were males. Of the 46 patients, 19 underwent F-18 FDG PET/CT for initial staging, nine underwent PET/CT for both initial staging and restaging and 18 underwent PET/CT for restaging. Seven patients underwent PET/CT for response evaluation. The sensitivity, specificity, PPV, NPV and accuracy were 100%, 100%,100%,100% and 96.4% for F-18 FDG PET/CT while 96.3%, 100%, 100% , 50% and 92.8% for CI at initial staging. In comparison to CI, PET/CT changed the management strategy in one out of 28 patients (3.5%) at initial staging. The sensitivity, specificity, PPV, NPV and accuracy were 100%, 91.7%, 93.7%, 100%, and 96.3% for PET/CT and 86.6%, 83.3%, 86.6%, 83.3%, and 85.2% for CI for restaging respectively. We found that FDG PET/CT had a higher positive likelihood ratio than CI to identify disease recurrences (12.0 vs. 5.2). In comparison to CI, PET/CT changed the management strategy in 4 of 27 patients (14.8%) at restaging. Response to chemotherapy was noted in two patients while disease progression was noted in five.
Conclusion: F-18 FDG PET/CT showed a higher diagnostic performance for initial staging and restaging of ACC patients as compared to CI. 18F-FDG PET/CT changed management strategy in a small number of patients and can be used for response evaluation to therapy. Research Support: Nil