PET-CT for staging pT4b melanomas prior to sentinel lymph node biopsy: a 5-year review

In this centre, patients with pT4b cutaneous melanoma are staged using 18F-FDG PET-computed tomography (PET-CT) prior to considering sentinel lymph node biopsy (SLNB). The objective was to assess the utility of PET-CT in terms of rates of detection of metastases leading to changes in planned treatment and if performing PET-CT was associated with a delay in surgical management. In this single-centre retrospective cohort study, 88 consecutive patients with pT4b melanoma were identified from February 2014 to May 2019. Data were collected from clinical records. Of the 88 patients, 76 patients underwent PET-CT and 16/76 (21%) of these demonstrated metastatic/potentially metastatic disease. In total 16/76 (21%) patients had positive findings on PET-CT, and of these 14 (18%) had alterations to their clinical care. Performing PET-CT did not significantly delay time to wide local excision (PET-CT median 74 days (range 16-220) vs. no PET-CT median 55 days (range 36-143) P = 0.56) or SLNB (PET-CT median 67 days (range 16-206) vs. no PET-CT median 124 days (range 45-203) P = 0.66). Of the 29 patients undergoing SLNB who had negative PET-CT findings, 12/29 (41%) demonstrated microscopic metastatic disease. At the median follow-up of 1.75 years, 28 patients (34%) had died. Median survival was not reached. Performing staging PET-CT prior to SLNB in patients with pT4b melanoma can reveal metastases in over a fifth of patients, leading to alteration in management without treatment delay. Due to the low sensitivity of PET-CT for small metastases, SLNB remains important for definitive staging.