Risk of non‐colorectal cancer‐related death in elderly patients with the disease: A comparison of five preoperative risk assessment indices

BACKGROUND: A considerable number of elderly patients with colorectal cancer (CRC) die of non‐CRC‐related causes. The Controlling Nutritional Status (CONUT) score, American Society of Anesthesiologists Physical Status classification, Charlson Comorbidity Index, National Institute on Aging, and National Cancer Institute Comorbidity Index, and Adult Comorbidity Evaluation‐27 score are all known predictors of survival in patients with CRC. However, the utility of these indices for predicting non‐CRC‐related death in elderly CRC patients is not known. METHODS: The study population comprised 364 patients aged 80 years or more who received curative resection for stage I–III CRC between 2000 and 2016. The association of each index with non‐CRC‐related death was compared by competing‐risks analysis such as the cumulative incidence function and proportional subdistribution hazards regression analysis as well as time‐dependent receiver‐operating characteristic (ROC) analysis. RESULTS: There were 85 deaths (40 CRC‐related and 45 non‐CRC‐related) during a median observation period of 53.2 months. Cumulative incidence function analysis identified CONUT score as the most suitable for risk stratification for non‐CRC‐related death. In proportional subdistribution hazards regression, risk of non‐CRC‐related death increased significantly as CONUT score worsened (2/3/4 vs. 0/1, hazard ratio 1.73, 95% confidence interval [CI] 0.91–3.15; ≥5 vs. 2/3/4, hazard ratio 2.71, 95% CI 1.08–6.81). Time‐dependent ROC curve analysis showed that CONUT score were consistently superior to other indices during the 5‐year observation period. CONCLUSIONS: The majority of deaths in elderly patients with CRC were not CRC‐related. CONUT score was the most useful predictor of non‐CRC‐related death in these patients.