Geographic variation in female breast cancer incidence and mortality in Canada.

BACKGROUND

Previous work has noted variability in cancer incidence and cancer-related outcomes according to place of residence. This study examined geographic variability in the incidence and mortality of breast cancer among females in Canada.

DATA AND

METHODS

Data from the 2021 Canadian Cancer Registry (breast cancer incidence) and the Canadian Vital Statistics - Death database (breast cancer mortality) were examined across provinces and territories, community sizes, and peer groups (i.e., clusters of health regions with similar socioeconomic and demographic characteristics). Age-standardized incidence rates (ASIRs) and age-standardized mortality rates (ASMRs) per 100,000 females per year and their rate ratios were calculated, as well as age group-specific and age-standardized stage-specific incidence rates.

RESULTS

From 2010 to 2020, the invasive breast cancer ASIR was 140.1 per 100,000 females annually, with marked geographic and community variation. Mean age at diagnosis was 62.7 years, and it was lowest in northern and remote regions. Three-quarters of cases were stages I and II, though stage-specific ASIRs varied. Overall ASIRs were highest in peer groups B (urban centres with large immigrant and racialized populations) and D (rural regions in Quebec, Ontario and the Prairies). They were lowest in peer groups F (Northern and remote regions with young populations), G (Montréal, Toronto, and Vancouver), and H (urban centres in Ontario and British Columbia). From 2010 to 2022, the ASMR was 28.3 per 100,000, highest in rural Eastern Peer Group E and lowest in large urban centres.

INTERPRETATION: The study found significant variability in female breast cancer incidence and mortality across the geographical classifications considered, highlighting the need for a closer look at regional- and individual-level factors and their respective associations with cancer incidence and outcomes.