Purpose

Women with a first-degree family history of breast cancer (FHBC) are sometimes advised to initiate screening mammography when they are 10 years younger than the age at which their youngest relative was diagnosed, despite a lack of unambiguous evidence that this is an effective strategy. It is unknown how often this results in women initiating screening earlier (< 40 years) than screening guidelines recommend for average-risk women.

Methods

We examined screening initiation age by FHBC and age at diagnosis of the youngest relative using data collected by the Breast Cancer Surveillance Consortium on 74,838 first screening mammograms performed between 1996 and 2016.

Results

Of the 74,838 women included in the study, nearly 9% reported a FHBC. Approximately 16.8% of women who initiated mammography before 40 years reported a FHBC. More women with a FHBC than without initiated screening < 40 years (48% vs. 23%, respectively). Among women with a FHBC who initiated screening < 40 years, 65% were 10 years younger than the age at which their relative was diagnosed.

Conclusion

Women with a first-degree relative diagnosed with breast cancer were more likely to start screening before 40 years than women reporting no FHBC, especially if their relative was diagnosed before 50 years.

Background

Women with a first-degree family history of breast cancer are often advised to begin screening when they are 10 years younger than the age at which their relative was diagnosed. Evidence is lacking to determine how much earlier they should begin.

Methods

Using Breast Cancer Surveillance Consortium data on screening mammograms from 1996 to 2016, the authors constructed a cohort of 306,147 women 30-59 years of age with information on first-degree family history of breast cancer and relative's age at diagnosis. The authors compared cumulative 5-year breast cancer incidence among women with and without a first-degree family history of breast by relative's age at diagnosis and by screening age.

Results

Among 306,147 women included in the study, approximately 11% reported a first-degree family history of breast cancer with 3885 breast cancer cases identified. Women reporting a relative diagnosed between 40 and 49 years and undergoing screening between ages 30 and 39 or 40 and 49 had similar 5-year cumulative incidences of breast cancer (respectively, 18.6/1000; 95% confidence interval [CI], 12.1, 25.7; 18.4/1000; 95% CI, 13.7, 23.5) as women without a family history undergoing screening between 50-59 years of age (18.0/1000; 95% CI, 17.0, 19.1). For relative's diagnosis age from 35 to 45 years of age, initiating screening 5-8 years before diagnosis age resulted in a 5-year cumulative incidence of breast cancer of 15.2/1000, that of an average 50-year-old woman.

Conclusion

Women with a relative diagnosed at or before age 45 may wish to consider, in consultation with their provider, initiating screening 5-8 years earlier than their relative's diagnosis age.