Background: Radiologic screening for breast cancer is performed with the goal of diagnosing the disease at an earlier stage, thus reducing morbidity and mortality. Screening recommendations for women at higher than average risk for breast cancer differ from those of women with an average risk, and include yearly breast MRI and mammography starting at a young age.
Objectives: Review the morbidity and mortality, and check whether the goal of early diagnosis was achieved in the participants of the High-Risk Ontario Breast Screening Program at the Princess Margaret Cancer Centre, Ontario Canada.
Methods: A prospective cohort study was conducted of 2,081 women participating in the Princess Margaret Cancer Centre high risk screening program 2011-2018. Demographic, imaging, and if applicable biopsies, diagnosis and treatment data were captured in a prospectively maintained database starting with each participant's enrolment in the program.
Results: A total of 32% of the participants were carriers of pathogenic variants in breast cancer related genes (BRCA, NF, CHEK2, TP53 etc.), 8% had a history of therapeutic chest radiotherapy, and the remaining 60% had a calculated elevated lifetime risk based on family history or personal risk factors, without an identifiable pathogenic mutation or previous radiation. During the follow-up period 89 breast cancer cases were diagnosed at the median age of 49 years. Median tumor size at diagnosis was 0.9 cm, correlating with a T1 disease. Nodal disease was found only in 4 cases. Breast cancer incidence was the same in the mutation carriers and chest radiotherapy groups, but 3-fold lower in the third group. Diagnosis of breast cancer was most commonly conducted by MRI imaging, and only 6% of cases were diagnosed based solely on mammography findings. Furthermore, 38 women died during follow-up, 29 of them (76%) were BRCA carriers who died from ovarian carcinoma.
Conclusions: Diagnosis at an early stage was achieved in this cohort of women followed in the high risk screening program. Most cases were diagnosed by MRI, thus emphasizing the importance of identifying women at high risk for breast cancer and referring them to the appropriate screening program.