Progression-Free Survival in Patients Receiving Chemotherapy Alone (C) or Chemotherapy with Bevacizumab (CB) for First-Line Treatment of KRAS Mutant Metastatic Colorectal Cancer in Community Oncology Settings.

Purpose: Bevacizumab is a standard first-line (L1) treatment for metastatic colorectal cancer (mCRC) patients regardless of RAS status. This retrospective study examined treatment patterns and outcomes in a community oncology sample of KRAS mutant mCRC patients treated with chemotherapy (C) or C plus bevacizumab (CB) in L1.

Methods: This study used medical records from the Vector Oncology Data Warehouse. Eligible patients were confirmed KRAS mutant mCRC and received L1 C or CB. Kaplan-Meier analysis assessed L1 progression-free survival (PFS) and overall survival (OS). Cox regression models examined the interaction of tumor location (R/L) with treatment.

Results: CB (n = 264) compared to C (n = 109) patients were younger, less likely performance status (PS) impaired, and more likely with liver metastases. Median unadjusted PFS was 10.41 months (95% CI 9.0-11.3) in CB and 7.66 months (95% CI 6.5-9.1) in C patients (p = 0.174). Median unadjusted OS was 26.91 months (95% CI 24.3-29.3) in CB and 23.33 months (95% CI 19.7-29.2) in C patients (p = 0.571). For patients with right- vs. left-sided tumors, C (but not CB)-treated patients had higher adjusted risk for progression (HR = 1.715, 95% CI 1.108, 2.653; p = 0.015).

Conclusions: CB- vs. C-treated KRAS mutant mCRC patients may have a meaningful PFS benefit. Patients with right-sided tumors treated with C were at higher risk for disease progression than patients with left-sided tumors. Tumor location had no significant effect on outcomes in the CB cohort.