Efficacy of adjuvant therapy in patients (pts) with AJCC v8 stage IIIA cutaneous melanoma.

Abstract

9518 Background: Pts with resected AJCC v8 stage IIIA melanoma have been under-represented in clinical trials of adjuvant drug therapy. The benefit of adjuvant targeted and immunotherapy in this population is unclear. Methods: In this multicenter, retrospective study, pts with stage IIIA melanoma (AJCC v8) who received adjuvant pembrolizumab or nivolumab (PD1), BRAF/MEK-targeted therapy dabrafenib + trametinib (TT), or no adjuvant treatment (OBS) were included. Recurrence free survival (RFS), distant metastasis free survival (DMFS), and toxicity rates were examined. Results: 613 pts from 34 centers across Australia, Europe and USA were included. The median follow-up was 2.6 yrs (IQR, 1.6-3.4 yrs). Pt characteristics and follow-up were similar across the cohorts (Table). Completion rates of 12-month PD1 and TT therapy were 57.0% and 69.2% respectively. 1-yr RFS was 93.3% (95% CI, 90.3-96.4) in PD1, 100% in TT and 91.3% (95% CI, 88.1-94.7) in OBS cohorts. 2-yr RFS was 79.3% (95% CI, 74.1-84.8) for PD1, 100% for TT and 84.3% (95% CI, 79.9-89.0) in OBS cohorts. 2-yr DMFS was 88.4% (95% CI, 84.3-92.8) in PD1, 100% in TT and 91.1% (95% CI, 87.7-94.7) in OBS cohorts. Risk of recurrence was associated with higher breslow thickness (HR 1.73, 95% CI 1.36-2.20), higher mitotic rate (HR 1.07, 95% CI 1.02-1.12) and neck as the site of nodal metastases (HR 2.71, 95% CI 1.45-5.06) in the overall cohort (p<0.05). Neck nodal metastases were associated with higher risk of recurrence in OBS cohort (HR 3.82, 95% CI 1.91-7.66; p<0.05) but not in the PD1 cohort. Rates of ≥ Grade 3 toxicities were 10.9% with PD1 and 20.0% with TT; discontinuation due to toxicity occurred in 25.0% and 30.0%, respectively. No new safety signals were observed. Rates of unresolved toxicity at last follow-up were 26.9% in PD1 and 7.7% in TT cohorts. Conclusions: In this large international study, adjuvant PD1 or TT did not significantly improve RFS or DMFS compared to OBS in pts with resected stage IIIA melanoma. Prognosis in stage IIIA melanoma is favourable and outcomes after adjuvant therapy in this population needs further study in prospective randomised trials. [Table: see text]