Metastasectomy and BRAF mutation; an analysis of survival outcome in metastatic colorectal cancer.

Background: Resection of oligometastases improves survival in metastatic colorectal cancer (mCRC). It is unclear whether the benefit is consistent for BRAF V600E mutant (MT) and wild type (WT) mCRC. This retrospective analysis explores the influence of BRAF MT on survival after metastasectomy.
Methods: Overall survival (OS) and recurrence-free survival (RFS) for BRAF MT and WT mCRC were evaluated. Survival was also analyzed in the cohort of BRAF MT with or without metastasectomy.
Results: Five hundred and thirteen patients who had undergone metastasectomy were identified, 6% were BRAF-MT. Median age 63. Median OS in BRAF MT vs WT: 25.7 vs 48.5 months (hazard ratio [HR] 1.95; 1.18-3.22). However, difference was not significant in a multivariate model. Right primary tumor, intact primary, >1 metastatic site, non-R0 resection, peritoneal metastasis, and synchronous metastasis were independent predictors of worse OS. Among 364 patients with RFS data there was no difference between BRAF MT and WT (16 vs 19 months, p=0.09). In another cohort of 158 BRAF-MT patients, OS was significantly better after metastasectomy compared to "no metastasectomy" (HR 0.34; 0.18-0.65, P= 0.001). Proficient mismatch repair status showed a trend toward worse survival after metastasectomy in BRAF MT (HR 1.71, P = 0.08).
Conclusion: OS did not differ after metastasectomy between BRAF MT and WT in a multivariate model. Median OS was >2 years in this study after metastasectomy among BRAFV600E MT patients suggesting a survival benefit of metastasectomy in this group where systemic therapeutic options are limited. Metastasectomy may be considered in carefully selected BRAF-MT patients.
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