Trends in survival from colonic cancer: the impact of subspecialization

Data from population-based registries have demonstrated a recent increase in case survival for colonic cancer which has been attributed to earlier diagnosis. The present study was performed to identify time trends in case survival for patients with colonic cancer in a single institution, and to identify factors associated with any such improvement.

Data regarding 1264 patients with colonic cancer who were diagnosed between January 1981 and December 1995 were obtained from the Royal Adelaide Hospital Cancer Registry. Prognostic factors examined were age, sex, Australian clinicopathologic stage (ACPS), differentiation and year of diagnosis. Survival analyses were performed using the Kaplan-Meier method, and differences between patient subgroups were tested using univariate and multivariate Cox analyses. Patterns of adjuvant therapy were stable throughout the study period.

The study group comprised 1264 patients. Key independent predictors of case survival after controlling for covariables were found to be earlier-stage disease (P < 0.001), moderately or well differentiated tumours (P < 0.001), and more recently diagnosed tumours (P = 0.011). Specifically, the 5-year survival rates (+/- SE) increased from 40.3% (+/- 3.2) for 1981-83 to 48.3% (+/- 3.3) for 1984-86 and 51.6% (+/- 2.1) for 1987-95. This increase in case survival was temporally associated with the establishment of a specialty colorectal surgical unit within the Royal Adelaide Hospital.

This study of patients with colonic cancer from a single institution confirms previously observed, population registry-based, increases in case survival over recent years. Such improvement was independent of trends in tumour stage and differentiation and the use of adjuvant therapies. This provides evidence that survival outcomes for colonic cancer are influenced by surgical expertise.