Senior woman having a mammography scan at hospital
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A new study suggests that mammography screening guidelines could be reconsidered for women with a first-degree relative diagnosed with breast cancer. Published in Cancer, the study evaluated the five-year risk for a woman developing breast cancer based on whether she had a mother, sister, or daughter with the disease, and the age of that woman at diagnosis. Current guidelines generally recommend screening women at average risk for breast cancer 10 years earlier than a relative’s diagnosis age.

“We hear about this recommendation, but could not really find any information on why 10 years was chosen,” explained first author Danielle Durham, data scientists from the University of North Carolina at Chapel Hill. “We wondered if 10 years was a good age to start early, or does it not need to be so early, or should it be even earlier.”

To answer that question, Durham and colleague analyzed data from the Breast Cancer Surveillance Consortium, a population-based resource that collected information on screening mammograms from 1996-2016 among women in the US.  In this paper, data from more than 300,000 women were included in the study. Researchers compared cumulative 5-year breast cancer incidence among women with and without a first-degree family history of breast cancer by relative’s age at diagnosis and screening age.

“We found that there does seem to be a benefit in starting screening mammograms early but maybe it does not need to be 10 years,” said Durham. “It could be as little as 5-8 years and depends on the age of the relative and also a woman’s other risk factors.”  Since many factors contribute to breast cancer, the authors stress the importance of consulting with a clinician when to begin screening based on a woman’s overall risk. “This approach might be more beneficial instead of having a broad recommendation for everyone,” added Durham.

The authors tracked the development of breast cancer according to the age of the diagnosed relative. Women reporting a first-degree family history of breast cancer had a higher 5-year cumulative incidence of breast cancer than women without (19.9 per 1000 vs. 13.0 per 1000). The 5-year cumulative incidence of breast cancer increased as the relative’s diagnosis age decreased.

“We found that for women who have a relative diagnosed at younger ages, 35-45, the age to start screening seems to be younger, closer to 5-8 years before the relative’s diagnosis age,” said Durham. At the other end or the range, if the relative was diagnosed at 70, then screening might start at age 47 which is close to the recommended age of 50 for starting screening mammograms for women with average risk. The study found that women with relatives diagnosed at age 50 or older should consider screening in their 40s.

The study did not analyze women by genetic risk factors, such as the BRCA gene mutation. These women may benefit from starting screenings earlier. The authors also suggest that women ages 30-39 with more than one first-degree relative diagnosed with breast cancer may wish to consider genetic counseling.

Increasing the age for initiating screening could reduce the potential harms of starting breast cancer screenings too early. These include increased radiation exposure and false positive results that could lead to unnecessary invasive procedures.

“When deciding when to begin screening, it’s about more than one factor in isolation,” said Durham. “Instead, it should include consideration of a woman’s overall story in consultation with her doctor.”

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