A first look at relative survival by stage for colorectal and lung cancers in Canada

Monitoring and reporting on cancer survival provides a mechanism for understanding the effectiveness of Canada's cancer care system. Although 5-year relative survival for colorectal cancer and lung cancer has been previously reported, only recently has pan-Canadian relative survival by stage been analyzed using comprehensive registry data. This article presents a first look at 2-year relative survival by stage for colorectal and lung cancer across 9 provinces. As expected, 2-year age-standardized relative survival ratios (ARSRS) for colorectal cancer and lung cancer were higher when the cancer was diagnosed at an earlier stage. The ARSRS for stage I colorectal cancer ranged from 92.2% in Nova Scotia [95% confidence interval (CI): 88.6% to 95.1%] to 98.4% in British Columbia (95% CI: 96.2% to 99.3%); for stage IV, they ranged from 24.3% in Prince Edward Island (95% CI: 15.2% to 34.4%) to 38.8% in New Brunswick (95% CI: 33.3% to 44.2%). The ARSRS for stage I lung cancer ranged from 66.5% in Prince Edward Island (95% CI: 54.5% to 76.5%) to 84.8% in Ontario (95% CI: 83.5% to 86.0%). By contrast, ARSRS for stage IV lung cancer ranged from 7.6% in Manitoba (95% CI: 5.8% to 9.7%) to 13.2% in British Columbia (95% CI: 11.8% to 14.6%). The available stage data are too recent to allow for meaningful comparisons between provinces, but over time, analyzing relative survival by stage can provide further insight into the known differences in 5-year relative survival. As the data mature, they will enable an assessment of the extent to which interprovincial differences in relative survival are influenced by differences in stage distribution or treatment effectiveness (or both), permitting targeted measures to improve population health outcomes to be implemented.