Breast Cancer Screening Study

Demonstration Data Project

Variations in Breast Cancer Pathology by Mammography Screening History and Methods: A Retrospective Cohort Study

Rationale

The effectiveness of breast cancer screening in the prevention of death from breast cancer has been the subject of large volumes of research in Canada and internationally. In contrast, the relationship between breast cancer screening and measures of the nature and extent of disease at diagnosis typically used clinically to determine disease prognosis, is not as well understood. Further, importance of the particular screening method used (for example, digital vs. film mammography) in detecting particular types of breast cancers is not yet well understood. To help address these evidence gaps, the objective of this study is to estimate, among Maritime residents diagnosed with breast cancer, the association between breast cancer pathology and a) their breast cancer screening history and b) the methods used in their breast cancer screening, focusing on mammographic technologies. The study will be conducted using parallel analyses of linked data from each Maritime province’s breast cancer screening and cancer registry databases.

Objectives

The purpose of this project is to determine associations between breast cancer screening participation and tumour characteristics among breast cancer patients in New Brunswick. Previous work has identified that participation in the screening program varies by geographic and socio-demographic characteristics (McDonald & Sherman, 2010). There is a need, however, to understand better how these variations translate into differences in favourability of tumour characteristics at time of detection. This study has three objectives:

  • Analyse differences in personal characteristics (e.g., age, urban/rural residence, immigrant status, education level, area income quintile) among women diagnosed with breast cancer as a function of screening program participation;
  • Analyse differences in health zone characteristics related to screening program administration (e.g., wait times, follow-up methods, methods to communicate information) among women diagnosed with breast cancer based on screening program participation; and
  • Analyse differences in characteristics of the detected tumours (e.g., histologic subtype (invasive ductal & lobular carcinoma, ductal carcinoma in situ), stage, axillary lymph node involvement, hormone receptor status, lymph vascular invasion) according to screening participation.

This study will make important contributions to health services research in New Brunswick by documenting the effectiveness of the screening program and by identifying how the program is affected by variations in provider practices across the province. The findings of the study can be extended to helping understand patterns, and improving participation rates in, other screening programs in New Brunswick and across Canada.