KRAS and NRAS mutations in Nordic population-based and real-world metastatic colorectal cancer cohorts.

BACKGROUND: KRAS and NRAS mutations (mt) are drivers in metastatic colorectal cancer (mCRC). We studied frequencies, characteristics, treatments, and outcomes of different KRASmt and NRASmt in population-based and real-world settings. METHODS: Three Nordic cohorts were combined and molecularly characterised for KRAS, NRAS, and BRAF-V600E hotspot mutations. RESULTS: Of 2649 mCRC patients, 2118 were molecularly classified. KRASmt were seen in 49%, NRASmt in 4%, RAS&BRAFwt in 33%, and BRAF-V600Emt in 14%. No differences in clinical characteristics were observed between KRASmt and NRASmt. Median overall survival (OS) was longest among RAS&BRAFwt, intermediate among KRASmt and NRASmt, and shortest among BRAF-V600Emt (28.3 vs 21.4 vs 26.3 vs 9.2 months, respectively). Among the eight most common KRASmt, the only clinical difference was that KRAS-G12S had more distant lymph node metastases (38% vs 18-27%, p = 0.041). KRAS-G12S had shorter OS than KRAS-G12V, KRAS-G12C, KRAS-G12A, and KRAS-G13D. The differences were smaller in treatment groups but withstood in multivariable models. The three most common NRASmt did not differ clinically. CONCLUSION: KRASmt and NRASmt are seen in 49% and 4% of mCRC, respectively. No clinically relevant differences were observed between different RASmt. KRASmt is a common subgroup for which the outcome hopefully can be improved with newly developed drugs.