Meropol NJ, et al. - In this study, researchers aimed to test their hypothesis that patients with metastatic colorectal cancer (mCRC) who had tumors with low thymidylate synthase (TS-L) expression would have a higher response rate to combined 5-fluorouracil, leucovorin, and oxaliplatin (FOLFOX) plus bevacizumab (FOLFOX/Bev) than those with high TS (TS-H) expression and that combined irinotecan and oxaliplatin (IROX) plus bevacizumab (IROX/Bev) would be more effective than FOLFOX/Bev in those with TS-H tumors. They recognized TS expression as prognostic. Compared to patients with TS-H tumors, those with TS-L tumors and received FOLFOX/Bev had a longer progression-free survival, along with a trend toward longer OS. No more benefit from IROX/Bev was evident among patients with TS-H tumors than from FOLFOX/Bev.