The use of PET/CT to detect early recurrence after resection of high-risk stage III melanoma, prior to the start of adjuvant therapy and during follow-up.

Abstract

e22039 Background: To date, international consensus concerning the use of PET/CT as a surveillance tool in the follow-up of high-risk melanoma patients after complete resection of disease is lacking. Moreover, with the rise of adjuvant therapy it seems appropriate to investigate the role of this imaging modality to exclude newly developed metastases after resection and prior to starting treatment. The aim of this study was to investigate the use of PET/CT as surveillance tool in the follow-up and prior to adjuvant therapy in asymptomatic patients with complete resection of stage IIIB and IIIC melanoma. Methods: Prospectively two cohorts were set up with stage III melanoma patients with complete resection of disease. In the first cohort (stage IIIB/C AJCC 7th) surveillance PET/CT was performed 6-monthly for two years if patients stayed asymptomatic with normal serum S100B, with a final scan at three years. In the second cohort (stage IIIB/C/D AJCC 8th) patients underwent one screening PET/CT after resection and prior to starting adjuvant treatment. Results: Eighty patients entered follow-up in cohort 1. Of these, the majority did not undergo surveillance scans, because they required treatment for newly detected clinical metastases. Thirty-five patients remained asymptomatic and were included in surveillance cohort one (105 scans) with a median follow-up of 33 months. Twelve patients (34%) developed a recurrence, seven (20%) of which were detected on the first scan at six months. Seven recurrences involved stage IIIC patients, five stage IIIB patients. Sensitivity and specificity were 92% and 100% respectively. Forty-two patients were included in cohort 2. Recurrence was suspected on nine scans, four (10%) of which were true positive. One patient proceeded to undergo a node dissection and then started adjuvant therapy. The other three patients had progressed to stage IV and therefore started radiotherapy and/or systemic immunotherapy. Five (12%) scans were false positive, the suspected lesions were not related to the preceded surgery. The number of scans needed to find one asymptomatic recurrence were 8.8 and 10.5 in cohort one and two, respectively. Conclusions: This study shows that PET/CT is a useful surveillance tool for detecting recurrence in asymptomatic high-risk resected stage III melanoma patients, especially within the first six months after surgery and therefore should be considered when monitoring these patients during follow-up as well as prior to starting adjuvant therapy.