Surveillance imaging with FDG-PET/CT in the post-operative follow-up of stage 3 melanoma.

9563 Background: With the evolving treatment landscape in metastatic melanoma, approaches to disease surveillance post resection in stage 3 disease requires reconsideration. We previously reported the outcomes of sub-stage-specific schedules of combined fluorodeoxyglucose-positron emission and computerized tomography (PET/CT) surveillance at high risk of relapse following surgery. The aim of this study was to provide an update on our surveillance protocol with an extended sample size and longer duration of follow-up. Methods: From 2009, patients with AJCC stage 3 melanoma underwent PET/CT scans according to pre-specified schedules based on Bayesian probabilities of sub-stage-specific relapse. Schedules were stage 3A: 6, 18 mo; stage 3B: 6, 12, 18, 24, 36, 48, 60 months; stage 3C: 6, 12, 18, 24, 36 months. Contingency tables were used to evaluate the sensitivity, specificity and predictive values of these schedules. Results: In total, 171 patients (3A: 34; 3B: 93; 3C:44) underwent 553 PET/CT scans with a median follow up of 47 months. Relapses were identified in 65 (38%) patients of which (72%) were asymptomatic at the time of radiologically documented relapse. False positive results occurred in 8%. The positive predictive value (PPV) of an individual scan for diagnosing true recurrence was 77% (64-87%). Negative scans at 6 months had negative predictive values (NPV) between 57% in Stage 3A to 69% in Stage 3B for relapse. Sensitivity and specificity of the overall approach of sub-stage-specific PET/CT surveillance for detecting disease relapse were 70% and 89%, respectively. Evaluable predictive values for detecting disease relapse were: stage 3A: PPV:56%, NPV:76%; 3B: PPV 83%, NPV 86%; stage 3C: PPV 84%, NPV 84%. 32 of 65 patients (49%; 3A: 1; 3B: 7; 3C: 2) underwent resection of relapsed disease and 10 of these patients remained free of disease with a median follow-up of 24 months. Conclusions: Sub-stage-specific PET/CT is effective in detecting asymptomatic recurrence in stage 3 melanoma, and is associated with a high rate of disease resection at relapse.