Background KRAS gene mutations are associated with a worse metastatic colorectal cancer (mCRC) prognosis.

Purpose To assess the effectiveness of the first-line treatment of mCRC according to KRAS mutational status.

Materials and methods Retrospective and observational study. It included patients who started chemotherapy for mCRC between October 2011 and June 2012. Effectiveness measure was the median progression-free survival (PFS) and response rate measured by RECIST criteria.

Results 79 patients. Mean age at diagnosis: 66 years old, 54% men. Median PFS was 11 months. The KRAS mutational status was determined for 88.6% of the patients, of which 52.9% was mutated. Median PFS was 13 and 10 months in wild-type and mutated KRAS patients respectively. Although statistically significant differences were not found for a 95% confidence interval (CI) (p = 0.058), they were considered a trend. A response was detected in 50% and 54.5% of wild-type and mutated KRAS patients respectively.

In the mutated KRAS group, median PFS was 9 and 10 months in bevacizumab and other regimes without targeted treatment respectively (p = 0.740). 51.9% and 20% of patients treated with bevacizumab and other regimes without targeted treatment respectively responded.

In the wild-type KRAS group, median PFS was 14 and 10 months in cetuximab/panitumumab and bevacizumab treated patients respectively (p = 0.136). 50% and 54.5% of patients treated with cetuximab/panitumumab and bevacizumab respectively responded.

In both groups, treatment was mostly associated with oxaliplatin and 5-fluorouracil or capecitabine.

Conclusions There was a trend to higher median PFS in wild-type KRAS patients, fitting with the worse prognosis in mutated KRAS patients. Response rate and median PFS were similar in wild-type and mutated KRAS patients regardless of the targeted therapy used.

No conflict of interest.