Demystifying BRAF Mutation Status in Colorectal Liver Metastases: A Multi-institutional, Collaborative Approach to 6 Open Clinical Questions.

OBJECTIVE
To investigate the clinical implications of BRAF mutated (mutBRAF) colorectal liver metastases (CRLM).


SUMMARY BACKGROUND DATA
The clinical implications of mutBRAF status in CRLM are largely unknown.


METHODS
Patients undergoing resection for mutBRAF CRLM were identified from prospectively maintained registries of the collaborating institutions. Overall survival (OS) and recurrence-free survival (RFS) were compared among patients with V600E versus nonV600E mutations, KRAS/BRAF co-mutation versus mutBRAF alone, MSS versus MSI status, upfront resectable versus converted tumors, extrahepatic versus liver-limited disease, and intrahepatic recurrence treated with repeat hepatectomy (RH) versus non-operative management.


RESULTS
240 patients harboring BRAF-mutated tumors were included. BRAF V600E mutation was associated with shorter OS (30.6 vs. 144 mo, P=0.004), but not RFS compared to nonV600E mutations. KRAS/BRAF co-mutation did not affect outcomes. MSS tumors were associated with shorter RFS (9.1 vs. 26 mo, P<0.001) but not OS (33.5 vs. 41 mo, P=0.3) compared to MSI-high tumors, while patients with resected converted disease had slightly worse RFS (8 vs. 11 mo, P=0.01) and similar OS (30 vs. 40 mo, P=0.4) compared to those with upfront resectable disease. Patients with extrahepatic disease had worse OS compared to those with liver-limited disease (8.8 vs. 40 mo, P<0.001). RH following intrahepatic recurrence was associated with improved OS compared to non-operative management (41 vs. 18.7 mo, P=0.004). All results continued to hold true in the multivariable OS analysis.


CONCLUSIONS
Although surgery may be futile in patients with BRAF-mutated CRLM and concurrent extrahepatic disease, resection of converted disease resulted in encouraging survival in the absence of extrahepatic spread. Importantly, repeat hepatectomy in select patients with recurrence was associated with improved outcomes. Finally, MSI-high status identifies a better prognostic group with regard to RFS while patients with nonV600E mutations have excellent prognosis.