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William J. Gradishar, MD, FACP, FASCO


Breast Cancer Screening of Women in Their 40s: Clinical Implications of Canadian Study

By: Chris Schimpf, BS
Posted: Tuesday, September 26, 2023

Anna N. Wilkinson, MD, MSc, CCFP, of the Department of Family Medicine at the University of Ottawa, Ontario, Canada, and colleagues conducted a study examining differences in the rates of diagnosis and survival among Canadian women who began screening for breast cancer in their 40s versus those who began in their 50s. Their findings, published in the Journal of Clinical Oncology, indicated that screening programs including women in their 40s were associated with a significantly higher rate of 10-year net survival—but not an increased rate of breast cancer diagnosis.

“Decisions around breast cancer screening in women in their 40s must weigh the potential harms and benefits of screening; however, this is not possible without accurate information concerning the impact of breast cancer on mortality in women age[d] 40 to 49 years,” the investigators noted. “This study elucidates the survival benefits [that] screening may provide for these women and highlights the importance of breast cancer as a cause of death in [this population].”

In Canada, the breast cancer screening programs of some provinces and territories include women aged 40 to 49, whereas others do not. Using the Canadian Cancer Registry, the researchers evaluated two cohorts of Canadian women diagnosed with breast cancer between 2002 and 2007: those aged 40 to 49 at diagnosis and those aged 50 to 59.

The investigators found that breast cancer was the primary cause of 10-year mortality in the cohort of women screened and diagnosed in their 40s, making up 90.7% of deaths. They observed that this cohort’s 10-year net survival rate of 84.8% (95% confidence interval [CI] = 83.8%–85.8%) was 1.9 percentage points higher than the rate of 82.9% observed among the cohort screened in their 50s (95% CI = 82.3%–83.5%; P = .001). They also reported the difference was significant among women screened between ages 45 and 49 P = .001) but not among those aged 40 to 44 (P = .328).

Disclosure: For full disclosures of the study authors, visit

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