Background/Objective: Studies have shown an association between colorectal cancer (CRC) sidedness and gene mutations that may affect CRC clinical behavior. This study examined the association between specific KRAS, NRAS, and BRAF hot-spot mutations and primary CRC sidedness. Methods: We performed a retrospective cohort analysis of 722 patients diagnosed with primary CRC and tested for KRAS, NRAS, and BRAF hot-spot mutations at the University of Texas Medical Branch (UTMB) from January 2016 through July 2023. Multivariable logistic regressions analyses were conducted. Results:KRAS, NRAS, and BRAF hot-spot mutations rates were 37.8%, 4.6%, and 6.1%, respectively. Right-sided primary CRC had the highest prevalence of mutated tumors (64%). KRAS and BRAF hot-spot mutations were significantly different according to tumor sidedness. KRAS p.Gly12Asp, p.Gly12Val, and p.Gly13Asp showed a significantly increased likelihood of right-sided primary CRC compared to KRAS wildtype, 128%, 134%, and 221% higher, respectively. Conversely, KRAS p.Gly12Val and p.Gly13Asp mutations were associated with decreased likelihood of rectal cancer (53% lower) and left-sided tumors (56% lower), respectively. BRAF p.Val600Glu mutation, as opposed to BRAF wildtype, was associated with a 278% higher likelihood of right-sided CRC. No significant associations were observed between NRAS mutations and primary CRC sidedness. Conclusions: In primary CRC, specific mutations in KRAS (p.Gly12Asp, p.Gly12Val, and p.Gly13Asp) and BRAF p.Val600Glu were associated with increased likelihood of right-sided tumors. KRAS p.Gly12Val and p.Gly13Asp mutations were associated with decreased likelihood of rectal cancer and left-sided tumors, respectively. These findings suggest that tumorigenesis and mutational processes differ based on tumor sidedness. Further studies are needed to substantiate these findings.

Background/Objective: The prognostic value of specific hot-spot mutations within KRAS, NRAS, and BRAF genes in metastatic colorectal cancer (mCRC) genes remains debatable. This study explores whether certain KRAS, NRAS, and BRAF mutations are associated with the risk of all-cause mortality in mCRC. Methods: We retrospectively analyzed records of 494 patients with mCRC treated at the University of Texas Medical Branch between January 2016 and July 2023. Data on genetic mutations and clinicopathological features were collected for this analysis. We estimated survival probabilities and conducted multivariable Cox proportional hazards regression to evaluate the impact of specific mutations on all-cause mortality risk. Results: KRAS c.35G>T (p.Gly12Val) and c.34G>T (p.Gly12Cys) mutations were significantly associated with an increased risk of all-cause mortality in the overall mCRC population and the treated mCRC subgroup. KRAS c.38G>A (p.Gly13Asp) was significantly associated with an increased risk of all-cause mortality in the treated mCRC subgroup but BRAF c.1799T>A (p.Val600Glu) was significantly associated with an increased risk of all-cause mortality in the overall mCRC population. No significant association was observed between NRAS mutations and mortality risk in mCRC, possibly due to their lower frequency or different biological effects compared to KRAS and BRAF mutations. Conclusions: These findings suggest that specific KRAS [c.35G>T (p.Gly12Val), c.34G>T (p.Gly12Cys), and c.38G>A (p.Gly13Asp)] and BRAF c.1799T>A (p.Val600Glu) mutations may have prognostic value in mCRC. However, given the single-center study design and lack of direct therapeutic implications, larger multicenter studies are needed to substantiate these results and better define the clinical relevance of these mutations.