Background: The prognostic impact of primary tumor location (right- vs left-sided) is well-established in stage III/IV colorectal cancer (CRC), with right-sided tumors associated with poorer outcomes. However, its prognostic role in stage II CRC remains unclear. This study investigates whether the worse outcomes observed in advanced right-sided cancers also apply to early-stage CRC, or if they may be influenced by other factors such as patient demographics and molecular biomarkers. Clarifying this could help improve risk stratification in clinical practice.
Methodology: For this study, we analyzed data of all Belgian patients diagnosed with stage II CRC in 2015-2016 (n = 3.278, data obtained from the Belgian Cancer Registry). Information on primary tumor location, demographics, pathologic T-category, molecular biomarkers (including microsatellite instability [MSI], BRAF, and KRAS status), and overall survival (OS) was collected.
Results: In the univariable analysis, patients with stage II right-sided colon cancer had a significantly worse OS than left-sided colon cancer. Furthermore, advanced age and pT4 were also associated with worse OS. However, in the multivariable analysis, only gender, age, and pathologic T-category significantly affected OS. Primary tumor location was not significantly associated with OS in the multivariable analysis. Furthermore, the molecular biomarkers did not show a significant effect in either analysis. However, due to the limited size of the multivariable cohort, these results should be interpreted with caution.
Conclusion: The primary tumor location is not an independent prognostic factor in stage II CRC with a confounding effect of age. Notably, molecular biomarkers did not affect the prognosis in either uni- or multivariable analysis.