Nature and management of melanoma recurrences following adjuvant anti-PD-1 based therapy.

Introduction: Approximately 50 % of resected stage II-IV melanoma patients develop recurrent disease by 5 years despite adjuvant anti-PD-1 therapy. Data to define best management of recurrences is lacking.

Methods: This was a multicentre, international, retrospective cohort study. Patients with resected stage II-IV melanoma who commenced adjuvant anti-PD-1-based therapy before January 2022 and later recurred were identified. Data on demographics, disease characteristics, recurrence patterns, management and outcomes were collected.

Results: 711 patients from 17 sites were included. Median age was 60 [range 16-92], 64 % were male, 2 % stage II, 91 % were stage III, 7 % stage IV. Median time to recurrence was 6.2 months (0-68.5) and median follow up time from recurrence was 19.8 months (range 0.2-73.1). 63 % recurred on anti-PD-1 therapy, 36 % off therapy [3 % < 6 months, 33 % > 6 months]. Initial recurrences were locoregional (LR) alone in 44 %, distant alone (DR) in 43 %, and 11 % in both sites. LR recurrences were managed with local therapy, alone (62 %) or with "second adjuvant" anti-PD-1 (14 %) or BRAF/MEK therapy (23 %); 12 m RFS2 was 25 %, 29 % and 69 % respectively (p = 0.0045). Definitive systemic therapy at first recurrence was given in 16 % LR and 86 % DR, with best outcomes for anti-CTLA4 + anti-PD-1 and trial combinations (24 m PFS 63 % and 69 %, respectively). The 24 m OS for the entire cohort was 65 %.

Conclusion: Most recurrences following adjuvant anti-PD-1 based therapy occur early and while still on drug. Outcomes are poor, regardless of site, timing of recurrence, and subsequent treatment.