[Standard Chemotherapy with Bevacizumab as First-Line Therapy for Metastatic Colorectal Cancer with RAS Mutation].

AIM: We examined the outcome of treatment with first-line chemotherapy with bevacizumab(Bmab)formetastatic colorectal cancer in our hospital to clarify the outcome for RAS mutant patients.

SUBJECTS AND METHODS: From January 2013 to April 2016, 28 patients who initiated standard chemotherapy(2 chemotherapeutic agents)with Bmab as the first-line regimen for metastatic colorectal cancer were enrolled in this retrospective study. Time to treatment failure(TTF)and overall survival(OS)were analyzed.

RESULTS: The median age was 66.5(46-81)years old, including 16 men and 12 women, 11 cases with RAS wild type, and 17 cases with mutant type. The response rate was 30.8% in 2 cases of CR, 6 cases of PR, 14 cases of SD, 4 cases of PD, and 4 cases with conversion surgery after chemotherapy. TTF was 6.5 months and OS was 32.1 months. Among those with RAS mutations, 3 cases received conversion surgery. TTF of the mutant and wild type were 6.3 and 5.6 months, respectively, and OS was 35.8 and 32.1 months, respectively, without any significant difference. In addition, excluding conversion cases, the OS of mutant and wild type patients was 22.7 and 29.5 months, respectively.

CONCLUSION: The outcome of treatment using first-line chemotherapy with Bmab for metastatic colorectal cancer with RAS mutations was retrospectively analyzed. There was no difference in therapeutic effect between RAS mutated and not, and it seems that an OS of more than 20 months can be expected for those with RAS mutations with this choice of treatment.