A population-based study from New South Wales, Australia 1996-2001: area variation in survival from colorectal cancer.

In this study, we have investigated the impact of area of residence on survival from colon and rectal cancer. Relative survival and relative excess risk of death from cancer were calculated for each of 17 health areas in New South Wales, Australia. There were statistically significant differences in survival across areas for both cancers after adjusting for demographic factors. The variation remained for colon cancer but was reduced for rectal cancer after adjustment for spread of disease at diagnosis. This persistent variation in colon cancer survival suggests that variation in treatment contributes to it, and there is separate evidence for such variation. Of the 7186 patients whose deaths within five years were attributable to colorectal cancer, 784 could have had their survival increased to more than five years if the excess risk of death in all areas was reduced to the 20th centile of its distribution. Estimates such as this can assist in prioritizing improvements in cancer services.