Background: There are increasing numbers of elderly patients with colorectal cancer (CRC). With the advance of cancer treatment in recent years, more elderly CRC patients receive curative surgery and multidisciplinary cancer treatment. The purpose of this study is to identify the risk factors of mortality and to improve survival of these patients. Methods: We recruited newly diagnosed CRC patients between 2005 and 2012 from Taiwan's nationwide health insurance database. Patients without definitive surgery for CRC were excluded. CRC patients aged < 65 years (non-elderly) were served as a reference group. The study cohort was followed until the end of 2013. Univariate and multivariate Cox proportional hazards models were applied to find the predictors of death among our study cohort. Results: During the 9-year study period, 10,818 (30.6%) died among 35,298 elderly CRC patients receiving definitive surgery, with a median follow-up period of 3.0 years. The median overall survival (OS) of the elderly patients was improved 1.4% per year (95% confidence interval [CI] 0.5–2.4%). Multivariate analysis showed that adjusted hazard ratios (HRs) for OS were 1.00, 1.23, 1.56, 2.15 in the patients aged 65–70, 70–75, 75–80, and ≥ 80 compared to those aged < 65, respectively. The older patients had a higher probability of having ≥ 2 underlying comorbidities (71.4% vs. 31.4%) and without postoperative treatment (42.1% vs. 28.8%), which might be associated with the increase of mortality risk. Conclusions: This largest cohort study demonstrated an increasing risk of mortality in elderly CRC patients, especially those with ≥ 2 underlying comorbidities and those without postoperative treatment.

HR, hazard ratio; CI, confidence interval; ^*Adjusted for underlying comorbidities.