Exactitude of Relative Survival Compared with Cause-Specific Survival and Competing Risk Estimations Based on a Clinical Database of Patients with Colorectal Carcinoma

PURPOSE: Relative survival estimates are widely used by cancer registries. They provide survival rates adjusted for causes of death other than cancer. They have rarely been used in clinical settings. When compared with cause-specific survival rates or competing risks analysis, their applicability is hardly known. This study compares these three outcome measures on the basis of a well-documented clinical database of patients with colorectal cancer. METHODS: We selected a consecutive series of 1,791 histopathologically completely resected colorectal cancer patients without neoadjuvant therapy from a prospective database from 1981 through 2006. Median follow-up was 4.7 (range, 0-23) years with only 3.1% patients lost. Cause-specific and relative survival are reported as failure rates as is the cumulative incidence in the presence of competing risks. RESULTS: The analysis comprised 1,081 patients with colon cancer and 710 patients with rectal cancer. Stage distribution was as follows: Stage I, 480 patients; Stage II, 785 patients; Stage III, 472 patients; and Stage IV, 54 patients. The cause-specific failure rate, the relative failure rate, and the cumulative incidence in the presence of competing risks at five years (95% CI) for all patients were 21.1 (range, 19.0-23.4) %, 22.5 (range, 19.6-25.2) %, and 19.0 (range, 17.0-20.9) %, respectively. CONCLUSION: Because we could demonstrate almost identical failure rates, we consider relative survival to be a powerful tool in clinical settings in which a comprehensive follow-up is not possible. It is especially useful as a reference parameter for clinical audit.