The impact of response-directed surgery and adjuvant therapy on long-term survival after neoadjuvant ipilimumab plus nivolumab in stage III melanoma: Three-year data of PRADO and OpACIN-neo.

101 Background: Neoadjuvant ipilimumab (IPI) + nivolumab (NIVO) has been shown to induce high pathologic response rates associated with an excellent relapse-free survival (RFS) in high-risk stage III melanoma. While OpACIN-neo tested different neoadjuvant IPI + NIVO regimens followed by therapeutic lymph node dissection (TLND) without adjuvant systemic therapy (ST), PRADO tested a personalized approach. In patients (pts) achieving a major pathologic response (MPR; ≤10% viable tumor), TLND and adjuvant ST were omitted, and pts with pathologic non-response (pNR; >50% viable tumor) were treated with adjuvant ST (BRAFi/MEKi or anti-PD1) ± radiotherapy after TLND. Here, we address 1) whether omitting TLND in MPR pts had an adverse effect on long-term survival and 2) whether adding adjuvant ST in pNR pts had a favorable effect on survival. Methods: The 3-year (3y) RFS and distant metastasis-free survival (DMFS) of pts with MPR and pNR from PRADO and OpACIN-neo were analyzed, comparing MPR pts with TLND versus without TLND and pNR pts with adjuvant ST versus without adjuvant ST. Survival rates were calculated and compared with Kaplan-Meier and log-rank methods. Associations between baseline characteristics and RFS or DMFS were examined by Cox regression analysis. Results: Median follow-up was 37.9 months in PRADO (cutoff Jan 8, 2023) and 46.8 months in OpACIN-neo (cutoff Feb 14, 2022). For MPR pts, TLND omission did not affect survival, with a 3y RFS of 93% versus 96% (p=0.47) and 3y DMFS 98% versus 98% (p=0.92) for pts without TLND (n=59) versus with TLND (n=53), respectively. In pNR pts, an indication for a RFS and DMFS benefit was seen favoring pts with adjuvant ST (n=17: n=10 BRAFi/MEKi and n=7 anti-PD1) over pts without adjuvant ST (n=23), with 3y RFS rates being 64% versus 35% (p=0.10) and 3y DMFS rates 70% versus 52% (p=0.24). Baseline clinical characteristics did not differ between PRADO and OpACIN-neo pts or were not associated with RFS and DMFS. Conclusions: Omitting TLND in MPR pts after neoadjuvant IPI + NIVO seems not to affect RFS/DMFS. Given the high survival rates, adjuvant ST is unlikely to give further benefit in these pts. In pts with pNR, addition of adjuvant ST with ongoing anti-PD1 or switch to BRAFi/MEKi appears to improve RFS and DMFS. Clinical trial information: NCT02977052 . [Table: see text]