Population-based analysis of breast cancer treatment by intrinsic sub-type in Manitoba, Canada

•The Manitoba Cancer Registry provides population-based data that is often difficult to capture.•Our 21 year screening program reduces lead and length time biases.•Descriptive studies help identify factors affecting treatment, recurrence, and survival.•Our results may be applied to other similar populations.

BackgroundFew descriptive epidemiological studies on the incidence, treatment and survival can accurately reflect a whole population. Manitoba, Canada has an accurate cancer registry, a drug information program network and a breast screening program since 1995. This combined with a stable population provides true population data that can accurately describe the region.MethodsUsing a retrospective cohort design all Breast Cancer cases were obtained from 2004-2010 (N = 5399) and grouped by Intrinsic sub-type. Identifiable co-morbidities, prescribed endocrine therapy, staging, surgery, treatment and overall and disease-free survival by intrinsic sub-type were evaluated.ResultsPrevalence of Luminal A (41.7%), Luminal B HER2- (15.6%), Luminal B HER2+ (8.9%), Basal-like(10.8%), and HER2+ non-luminal (5.1%) were consistent with other descriptive studies in Canada and Spain. Over this time period the number of lumpectomies increased 1.7% per year (P = 0.007). There was a steady increase of 3.4% per year in the use of aromatase inhibitors (P = 0.005). Pre-menopausal patients had an increased proportion of HER2+ and Basal-like sub-types. The 7 year overall/disease-free survival percentages for Luminal A, Luminal B HER2-, Luminal B HER2+, Basal-like, and HER2+ non-luminal were 88.7%/83.6, 78.2%/73.0, 81.5%/73.3%, 67.7%/63.2%, 70.4%/65.6% respectively.ConclusionsReasons for variability in the prevalence of intrinsic sub-type by region is not fully understood. Manitoba is unique due the stability of the population, completeness of the registry and length of breast cancer screening program. Few true population-based studies grouped by intrinsic sub-type are available.ImpactDescriptive epidemiological studies guide future research by identifying factors that can affect treatment, recurrence, and survival.