Survival Outcomes in Patients With RAS Wild Type Metastatic Colorectal Cancer Classified According to Köhne Prognostic Category and BRAF Mutation Status

Abstract

Background: Köhne prognostic score is used to classify patients with metastatic colorectal cancer (mCRC) as high, intermediate, or low risk. Using data from 2 phase III trials, we analyzed survival in patients categorized according to Köhne prognostic category and virus-induced rapidly accelerated fibrosarcoma murine sarcoma viral oncogene homolog B (BRAF) mutation.

Patients and methods: PRIME (Panitumumab Randomized Trial In Combination With Chemotherapy for Metastatic Colorectal Cancer to Determine Efficacy) (first-line) and 20050181 (second-line) were studies of chemotherapy with or without panitumumab. Progression-free survival (PFS) and overall survival (OS) were analyzed retrospectively in rat sarcoma viral oncogene homolog (RAS) wild type (WT) and RAS WT+BRAF WT mCRC in each Köhne category, and in BRAF mutant (MT) mCRC.

Results: In PRIME (n = 495) and 20050181 (n = 420), 53 (11%) and 44 (10%) patients, respectively, had BRAF MT mCRC. Of the RAS WT+BRAF WT/unknown populations, 85/267/90 and 82/211/83 were categorized as high/medium/low risk, respectively. PFS and OS hazard ratios (HRs), adjusted for Köhne group, for patients with RAS WT + BRAF WT/unknown mCRC favored panitumumab with chemotherapy versus chemotherapy alone in both studies. In PRIME, the PFS HR was 0.74 (95% confidence interval [CI], 0.61-0.90) and OS HR was 0.78 (95% CI, 0.64-0.95). In 20050181, PFS and OS HRs were 0.80 (95% CI, 0.65-0.99) and 0.78 (95% CI, 0.62-0.99), respectively. Median PFS and OS were lower in patients with BRAF MT mCRC than in any of the 3 risk categories for patients with RAS WT+BRAF WT/unknown mCRC.

Conclusion: During first- and second-line treatment, Köhne prognostic score allows accurate risk classification in RAS WT mCRC. BRAF MT mCRC should be classified as high risk regardless of other parameters. Panitumumab with chemotherapy might provide survival benefits versus chemotherapy alone in RAS WT and RAS WT+BRAF WT/unknown mCRC, overall and across risk categories.

Keywords: Chemotherapy; Overall survival; Panitumumab; Prognosis; Progression-free survival.