Clinical characteristics and prognosis of different primary tumor location in colorectal cancer: a population-based cohort study

TLDR: Patients’ diagnoses were identified using the Surveillance, Epidemiology, and End Result database between 2006 and 2015 and it was demonstrated that the prognoses of Patients with left-sided cancers were better than those of patients with right- sided cancers regardless of stage.

Abstract: Emerging data have shown that patients with left-sided cancers have better survival than patients with right-sided cancers in terms of metastatic colorectal cancer. However, the available information and findings remain limited and contradictory in localized colorectal cancer. This study aimed to evaluate the clinical characteristics and prognosis of primary tumor location (PTL) in colorectal cancer. Patients’ diagnoses were identified using the Surveillance, Epidemiology, and End Result database between 2006 and 2015. The analyses were further stipulated to patients with primary cancer site, histology, and stage information. The correlations between PTL and overall survival (OS) were assessed. Compared with left-sided tumors, right-sided tumors were more likely to develop into T3 cancers (50.0% vs. 44.8%), T4 cancers (15.8% vs. 12.3%), mucinous or mucin-producing adenocarcinoma (10.8% vs. 5.0%), and signet ring cell carcinoma (1.4% vs. 0.7%), P < 0.01, respectively. Patients with right-sided tumors showed inferior OS (56.1% vs. 60.2%), and the hazard ratio was 1.224 (95% CI, 1.208–1.241, P < 0.001) in all stages. Stage-specific Cox regression analysis revealed that patients with right-sided tumors also showed inferior OS in every stage (respectively, P < 0.05) than left-sided tumors. This study demonstrated that the prognoses of patients with left-sided cancers were better than those of patients with right-sided cancers regardless of stage. PTL can be a prognosis factor in colorectal cancer. We encourage developing clinical and translational studies to elucidate the causative relationship between PTL and prognosis.