Abstract
BACKGROUND: Colorectal cancer is one of the leading cancers worldwide. This study aimed to investigate the mortality differences between 2 primary tumor locations, the proximal/distal colon and rectosigmoid junction (RSJ)/rectum, after adjusting for comorbidities. METHODS: The Taiwan Cancer Registry linked with Taiwan's National Health Insurance Research Database was used to estimate the 5-year mortality rate among patients with colorectal cancer. A total of 73 769 individuals were enrolled in the study, which included 44 234 patients with proximal and distal colon cancers and 29 535 patients with RSJ and rectal cancers. Potential mortality risk was calculated using Cox regression analysis. RESULTS: The mortality rates due to the location of the cancer in the proximal/distal colon and RSJ/rectum were 45.27% and 42.20%, respectively. After adjustment for age, sex, comorbidities, and clinical stages, the proximal/distal colon had a 1.03-fold higher 5-year overall mortality rate than RSJ/rectal cancer (95% confidence interval = 1.00-1.05). Proximal and distal colon cancers had a worse prognosis and survival than RSJ and rectal colon cancers in women and older patients (⩾70 years). Comorbidities had different effects on mortality in the proximal/distal colon and RSJ/rectum. CONCLUSIONS: Tumor location is associated with the prognosis of patients with colorectal cancer. It is important to treat patients beyond their cancer treatment, and to manage their comorbidities.