Role of F-18 FDG PET/CT in restaging of patients with renal cell carcinoma: experience at a single tertiary care centre

Objectives In the present retrospective study, we evaluated the diagnostic performance of F-18 FDG PET/CT in the restaging of clear cell renal cell carcinoma (RCC) and its comparison with the conventional imaging.

Methods A total of 139 patients (male = 94, female = 45; median age = 53.3 years; range = 18-81 years) from June 2013 to November 2015, with histopathological proof of renal cell carcinoma were evaluated in this retrospective study. All the patients underwent whole-body F-18 FDG PET/CT for restaging of the disease after initial nephrectomy or after chemotherapy with clinical or radiological suspicion of recurrence. FDG PET/CT findings were evaluated by two experienced nuclear medicine physicians and any abnormal FDG uptake on PET images was correlated with lesion on CECT and taken as positive. For the validation of the imaging results, histopathological examinations, clinical or imaging follow up were taken as reference standard. Conventional anatomical images (USG / CT or MR scans) were also evaluated for comparison (wherever available).

Results Of the 139 patients, 115 patients had clear cell carcinoma on histopathology, 8 chromophobe, 10 papillary carcinoma and 6 sarcomatoid carcinoma. FDG PET/CT revealed positive findings in 72 patients and negative in 67 patients. Out of 72 PET positive patients, 29 had regional disease (renal bed or retroperitoneal disease), regional and distant metastases in 18 patients and only distant metastases in 25 patients. Sixty-eight patients were true positive (TP), 4 patients false positive (FP), 64 patients were true negative (TN), and 3 patients were false negative (FN). FDG PET/ CT had shown sensitivity, specificity, positive predictive value, and negative predictive values of 95.7%, 94.1%, 94.4%, and 95.5% respectively. Conventional imaging (CECT/MRI or USG) were available in 39 patients (TP -20, FP-14, FN-2 and TN -3) and revealed sensitivity, specificity, positive predictive value, and negative predictive values of 90.9%, 16.2%, 58.8%, and 60.0 % respectively.

Conclusions Our results indicate that F-18 FDG PET have very high specificity, PPV and NPV as compared to conventional imaging. FDG PET/CT had shown an excellent diagnostic performance and it performed better than conventional imaging in restaging of renal cell carcinoma patients.