Abstract
9555 Background: Information on the use of radiotherapy in anti-PD-1 monoclonal antibody-treated melanoma pts is limited although some data support a synergistic effect. Methods: We investigated the influence of simultaneous radiotherapy in a multicenter ambispective cohort of advanced melanoma patients initiating pembrolizumab between May 2014-sept 2015 (CCTIRS, #15.640). Palliative or curative intent of radiotherapy was recorded. Overall (OS) and progression-free (PFS) survivals were analyzed using Kaplan-Meier survival analysis and Log rank tests were used to compare curves. Results: 663 pts (151 pts with brain metastases) were included in 40 French centers, with 125 pts (19%) receiving simultaneous radiotherapy (43 pts with ≥1 brain metastasis, 82 without). No significant difference in baseline LDH level, ECOG performance status, N of metastatic sites, previous treatment lines or post-progression therapies was observed between pts who did or did not receive radiation. As compared to pts without brain metastases, radiotherapy was performed in brain metastases pts closer to initiation of pembrolizumab (median 1.1 m vs 3.7 m, p = 0.009) and more frequently with a curative intent (72% vs 37%, p < 0.001). Globally, OS was longer in radiated vs non-radiated pts (median 18.9 m vs 12.5 m, HR:0.78, 95%CI: 0.57-0.96). This benefit was mainly driven by the pts with brain metastases (OS: median 26.0 m vs 6.0 m, HR:0.35, 95%CI:0.22-0.56, p < 0.001)(PFS: 6.4 m vs 2.5 m, HR:0.54, 95%CI:0.36-0.81, p < 0.002). No significant difference was seen for OS in radiated pts without brain metastasis, who were mainly radiated later and for palliative reasons and had shorter PFS (2.8 vs 3.4 m, HR 1.32, P < 0.03). Conclusions: Simultaneous radiotherapy may enhance efficacy of anti-PD1 therapy, particularly when initiated early and in brain metastases pts. Controlled studies are needed. Clinical trial information: 15.640.
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