Analysis of neoadjuvant nivolumab and ipilimumab for clinical stage III melanoma using the SWOG S1801 event-free survival definition.

e21563 Background: Perioperative pembrolizumab to advanced melanoma, as shown SWOG S1801 trial, was associated with a longer event-free survival (EFS) than those who received adjuvant pembrolizumab (EFS at 2y: 72% vs 49%, respectively). EFS, as defined in this trial, encompasses important factors related to neoadjuvant therapy in clinical practice. So far, there is no data of EFS rate for melanoma patients(pts.) treated with neoadjuvant nivolumab and ipilimumab, which is associated with more response rate but also more toxicity. Methods: We conducted a retrospective analysis of pts. with clinical stage III melanoma treated with neoadjuvant nivolumab 3mg/kg + ipilimumab 1 mg/kg (N3+I1) for two cycles followed by surgery and adjuvant therapy at AC Camargo Cancer Center. We applied the SWOG S1801 EFS definition (which includes inability to receive surgery, to start adjuvant therapy, melanoma recurrence and death) to this cohort. Results: Between Jan 2019 and Jan 2024, 37 pts. with clinical stage III melanoma treated with neoadjuvant N3+I1 were identified. Gender: 25 males (67%), median age (years): 58 (range: 31-78), BRAFV600 mut: 25(67%), Stage AJCC 8 th edition: IIIB = 23 (62%), IIIC = 12 (32%), IIID = 2(6%). G3/G4 immune-related adverse events (irAE): 11 patients (30%). Two out 37 pts. did not complete the programmed neoadjuvant cycles due to toxicity (1 = colitis, 1 = myositis). Three pts. (8%) were unable to receive surgery: irAE = 1, metastatic disease = 2. All pts. who underwent surgery (n = 35) achieved R0 resection and started adjuvant therapy within 84-days after the procedure. Major pathological response (MPR) = 23 pts(66%) and non-MPR = 12 pts.(34%). There were 4 melanoma relapses after starting adjuvant therapy (11%). The total number of events was 7 (19%). In a median follow-up of 16.1 months(range:13.9-25), the landmark analysis of EFS at 2 years was 73% (95%CI, 49 to 87). Relapse-free survival(RFS) for MPR at 2 years: 96%. Conclusions: Neoadjuvant N3+I1 seems to have similar EFS compared to SWOG S1801, but numerically more MPR rate and fewer events of progression, relapse and/or death. Table: see text