Assessment of survival and prognostic factors in metastatic colorectal cancer patients treated with first-line bevacizumab-based therapy

Purpose: Colorectal cancer (CRC) is a significant cause of cancer mortality worldwide. Survival has improved with bevacizumab in metastatic CRC treatment. Our purpose was to analyse survival and prognostic factors in metastatic CRC patients treated with first-line bevacizumab-based treatment. Methods: Files of CRC patients were examined retrospectively and 360 patients treated with first-line bevacizumab were included. Objective response rates (ORRs), median progression-free and overall survival (PFS and OS) of the patients were calculated. Survival was analyzed with the Kaplan-Meier method. Log-rank test and Cox regression model were used for univariate and multivariate analyses, respectively. Results: Median age at diagnosis was 59.5 years. Of the patients 74.4% had initially stage IV disease. Median PFS was 8.5 months, median OS 25.3 months and overall response rate (ORR) 51.4%. ORRs, median PFS and OS of KRAS mutant and wild-type or unknown patients were statistically similar. In left-sided disease, median PFS and OS (9.6 and 27.1 months) were superior compared to right-sided disease (7.3 and 19.4 months) (p=0.005 and 0.02, respectively). Primary disease location, histopathologic grade, primary surgery and metastasectomy affected OS significantly. Histopathologic grade (hazard ratio=1.77, p=0.002) and metastasectomy (hazard ratio=0.48, p=0.001) were independent prognostic factors. Conclusions: Our study confirmed that after bevacizumab-based treatment, KRAS status might not be a prognostic factor. We have also shown that left CRCs have more favorable outcomes than right CRCs in bevacizumab therapy. Additionally, even in metastatic setting histopathologic grade of the primary CRC together with metastasectomy are independent prognostic factors.