Survival after colon cancer 1973-1990 in Sweden. Convergence between catchment areas.

The objective of the study is to analyze the temporal trends in relative survival among patients with colon cancer in catchment areas of hospitals of different categories and regions in Sweden. In Sweden, cancer of the colon is the second most common type of cancer in women and the third most common in men, afflicting approximately 3000 individuals annually. During the past decades, survival has improved, but it is not clear what factors have contributed to this development. Changes in the natural history of the disease, altered alimentary habits, advances in diagnosis, and treatment have been suggested. The effects of centralized care still are debated. Longitudinal observational study of relative survival of all patients with colon cancer from 1973 to 1993 in Sweden (n = 41,700) by period of diagnosis and hospital category of primary catchment area was conducted. Multivariate analyses of relative hazards of any interaction between length of follow-up, period of diagnosis, hospital category of the primary catchment area, age at diagnosis, and region were performed. Relative survival in patients with colon cancer improved substantially from 1973 through 1990. The prognosis in patients from primary catchment areas of regional-university hospitals did not change during this period, and the prognostic improvement was noted only in county and local hospital areas, where survival approached that of regional hospitals. Although new management regimens may have been introduced unevenly, improved perioperative care best explains this convergence. Low-incidence regions showed the lowest survival, but this improved with time, although not significantly. Although survival in patients with colon cancer improved and convergence between different catchment area categories was seen, a large initial gap as well as a remaining difference may warrant future monitoring to ensure equal prognosis, irrespective of domicile.