CA19-9 level as a prognostic and predictive factor of bevacizumab efficacy in metastatic colorectal cancer patients undergoing oxaliplatin-based chemotherapy

The prognostic and predictive values of carbohydrate antigen 19-9 (CA19-9) levels in metastatic colorectal cancer (mCRC) remain unclear. We reviewed all mCRC patients at a single institution to evaluate the relationship between CA19-9 levels and survival. Two hundred and fifty-two patients underwent first-line chemotherapy using oxaliplatin-based regimens between April 2005 and December 2009. The relationship between baseline CA19-9 levels and survival was analyzed. Moreover, we evaluated the relationship between baseline CA19-9 levels and clinicopathological factors. One hundred and fifty patients had elevated baseline CA19-9 levels (elevated group), and 79 patients had normal baseline CA19-9 (normal group) levels. Both KRAS and BRAF mutation rates were higher in the elevated group than in the normal group. Elevated CA19-9 level was a poor prognostic factor compared with normal CA19-9 levels (P = 0.0021). In the elevated group, the median survival time with bevacizumab was significantly longer with bevacizumab than without it (median OS, 27.8 vs. 15.3 months, P = 0.0019). However, the median survival time was not different with or without bevacizumab in the normal group (median OS, 36.5 vs. 38.0 months, P = 0.9515). Our results suggest that baseline CA19-9 level is an independent prognostic factor in mCRC patients, and it correlated with the KRAS/BRAF mutation status. Bevacizumab exhibits clinical activity only for high CA19-9 levels in mCRC.