Resection of metastases in patients with BRAF mutated metastatic colon cancer: results of a multicenter retrospective study

Abstract

Introduction: local treatment of metastases is an integral part of colon cancer treatment. However, there is not enough data on the efficacy of surgical resection of metastases in patients with a BRAF gene mutation to recom‑mend this approach in routine practice. We initiated a retrospective multicenter study to assess the incidence of BRAF gene mutations in patients with metastatic colon cancer and to study the efficacy of metastasectomy in this group of patients.Materials and methods: we selected all patients who underwent surgical resection of metastases in various sites from the database of patients with BRAF gene mutations created as a result of a multicenter retrospective study with participation of 7 clinics in the Russian Federation. All 57 patients with RAS gene mutations and 43 patients with wild‑type RAS and BRAF genes who also underwent surgical resection of metastases at any stage of treatment were selected from the register of the Chemotherapy Department No. 2 of the NMRC of Oncology named after N. N. Blokhin for comparative analysis. Disease‑free survival and overall survival were used as primary efficacy criteria.Results: we found 26 patients with BRAF gene mutations who underwent surgical resection of metastases. When comparing disease‑free survival, the worst median was achieved in the group of patients with BRAF gene mutations: 7 months versus 14 months in patients with RAS gene mutations (HR 0.4, 94 % CI 0.23–0.7, P = 0.006); median disease‑free survival was not achieved in the wild‑type RAS and BRAF group (HR 0.2, 95 % CI 0.11–0.45, P <0.001).The median overall survival in the BRAF gene mutation group was 26 months versus 38 months in the RAS gene mutations group (HR 0.8, 95 % CI 0.33–1.98, P = 0.6) and 49 months in the wtRAS/wtBRAF group (RR 0.46, 95 % CI 0.17–1.24, P = 0.1). Resection of recurrent tumors in patients with metastases in retroperitoneal lymph nodes was associated with extremely low disease‑free survival (2 months); at the same time, disease‑free survival was 7 months after resection of isolated metastases in the liver and 8 months for metastases in the peritoneum.Conclusion: prognosis of patients with a BRAF gene mutation after surgical resection of metastases is worse than in patients with a different mutation phenotype. Nevertheless, literature data, as well as the results of our study, confirm the possibility of performing metastasectomy with careful selection of patients.