Comparison of adjuvant targeted and anti-PD1 immunotherapy in BRAF-mutated stage III cutaneous melanoma: Retrospective, single center cohort study.

Abstract

e21558 Background: Targeted therapy (TT) and anti-PD1 immunotherapy (IT) are standard of adjuvant stage III melanoma treatment. However, no comparative prospective randomized trials (head-to-head) were conducted. Data limited to a few retrospective studies. Both treatment regimens were registered in Russia in 2019. We aimed to compare adjuvant options in Russian melanoma pts. Methods: We conducted a single-center retrospective observational study approved by the IRB. We included all pts age 18 and older (one patient, female, was 14) with BRAF-mutated stage III melanoma who were treated at the N.N.Blokhin NMRC of Oncology MoH and received adjuvant therapy between Jan 2019 and Dec 2022. The primary endpoint was RFS, the secondary endpoint - OS. Cox regression analysis was used to identify prognostic factors for RFS (including substage, thickness and ulceration of primary tumor). Results: A total of 209 pts were included, mostly BRAF V600E/K, 92 (44%) male and 117 (56%) female. Median age was 50,6 years (range: 14-81). 93 (44,4%) pts received TT, 103 (49,3%) pts received IT and 13 (6,3%) didn’t receive adjuvant therapy (observation only). The observation group wasn’t analyzed due to a small number of pts. At a median follow-up of 27 mo, median RFS was 30 mo (95% CI 23-56) in TT group and wasn’t reached in IT group; median OS wasn’t reached in both groups. There weren’t statistical differences between TT and IT groups in RFS (HR 0,84, 95% CI 0,53-1,34, p = 0,47) and OS (HR 0,59, 95% CI 0,26-1,34, p = 0,21), even though at 12 mo, the rate of RFS was higher in the TT group (91.4%) compared IT group (67%), at 18 mo – 79,5% and 63,1%, 24 mo – 68,8% and 61,1% respectively. TT group had numeric but not significant RFS benefit in most subgroups. HR values for substage, thickness and ulceration are presented in the table below. Tx+T0 pts (TT, n = 7; IT, n = 13) and unknown status of ulceration (TT, n = 7; IT, n = 16) was not presented for some pts. Conclusions: Differences between TT and IT wasn't reached at a median follow-up of 27 mo. But IT-treated pts had more and earlier recurrences than TT pts. In BRAF mutated pts, adjuvant TT might prevent early recurrences more effectively than IT. These results need to be interpreted with caution given its retrospective and non-randomized nature and potential selection biases. Additional time to follow-up and biomarker analysis was planned. [Table: see text]