KRAS Mutation Status in Bulgarian Patients with Advanced and Metastatic Colorectal Cancer.

somatic variants are predictors of resistance to anti-EGFR therapy for colorectal cancer (CRC) and affect the outcome of the disease. Our study aimed to evaluate the frequency of , with a focus on variants, and their association with tumor location and some clinicopathological characteristics in Bulgarian CRC patients. We prospectively investigated 236 patients with advanced and metastatic CRC. Genomic DNA was extracted from FFPE tumor tissue samples, and commercially available kits were used to detect gene somatic mutations via real-time PCR. A total of 115 (48.73%) patients tested positive for mutations, with 106 (44.92%) testing positive for mutations. The most common mutation in exon 2 was c.35G>T p.Gly12Val (32.56%). We did not find a significant difference in mutation frequency according to tumor location. However, patients with a mutation in exon 4 of were 3.23 times more likely to have a tumor in the rectum than in other locations (95% CI: 1.19-8.72, = 0.021). Studying the link between tumor location and mutations in exon 4 is crucial for better characterizing CRC patients. Further research with larger cohorts, especially in rectal cancer patients, could provide valuable insights for patient follow-up and treatment selection.