Overall survival (OS) with encorafenib (enco) plus cetuximab (cetux) in BEACON CRC: Effect of prior therapy for BRAF V600E-mutant metastatic colorectal cancer (mCRC)

3583 Background: Enco + cetux (doublet) has been approved in the US, EU, and Japan for the treatment of BRAF V600E-mutant mCRC after progression on 1–2 prior regimens. In the BEACON CRC study (NCT02928224), median OS (95% CI) with the doublet was 9.3 months (8.0–11.3) compared with 5.9 months (5.1–7.1) with cetux + irinotecan or FOLFIRI (control) in patients (pts) with BRAF V600E-mutant mCRC (HR 0.61 [95% CI: 0.5–0.8]). This post-hoc analysis investigates OS by prior therapies to the doublet treatment in pts with BRAF V600E-mutant mCRC from the BEACON CRC study. Methods: OS of pts treated with the doublet or control were compared according to prior treatment with bevacizumab, oxaliplatin, or FOLFOXIRI and duration of prior anticancer therapy (ACT). Results: The proportion of pts in the doublet and control arms who received prior bevacizumab were 64% and 55%, respectively. Of pts who had one prior therapy, 95% and 88% received prior oxaliplatin and 20% and 14% received prior FOLFOXIRI, respectively. OS by prior treatment in the doublet and control arms is shown in the table. In the doublet arm, pts who had bevacizumab < 4 months before start of study treatment had a median OS of 8.3 months (95% CI: 6.2–11.2); those who had bevacizumab ≥4 months prior had a median OS of 10.7 (95% CI: 7.5–17.7). Within each treatment arm, OS was similar regardless of prior treatment with oxaliplatin or FOLFOXIRI. The duration of prior ACT was similar across study arms, ranging from 5.6–5.8 months for the first line of ACT. Conclusions: In the BEACON CRC study, pts treated with the doublet for BRAF V600E-mutant mCRC demonstrated similar OS regardless of prior therapies or duration of prior therapy use. This exploratory post-hoc analysis provides data that reflect the prior treatment landscape clinicians may face when deciding subsequent treatment regimens for pts with BRAF V600E-mutant mCRC. Clinical trial information: NCT02928224. [Table: see text]