New data will add fuel to the ongoing debate over the age at which mammography screening for breast cancer should begin. Many guidelines recommend starting at age 50.

But yearly mammography between the ages of 40 and 49 years was associated with a “substantial and significant” 25% reduction in breast cancer mortality during the first 10 years of follow-up, according to new data from the UK Age Trial.

The researchers calculated that 1150 women needed to undergo screening in the age group of 40-49 years to prevent one breast cancer death, or about one breast cancer death prevented per 1000 screened.

However, they also note that in the years since the trial first began there have been improvements in the treatment of breast cancer, so “there might be less scope for screening to reduce mortality in our current era.”

The study was published online August 12 in Lancet Oncology.

“Our results do indicate that screening before age 50 does indeed prevent deaths from breast cancer, with a minimal additional burden of overdiagnosis,” said lead author Stephen W. Duffy, MSc, director of the Policy Research Unit in Cancer Awareness, Screening and Early Diagnosis, at Queen Mary University, London, UK.

That said, Duffy explained they do not expect policymakers to extend the age range on the basis of these results alone. “For one thing, they will want to consider costs, both human and financial,” he told Medscape Medical News. “For another, at this time, the services are concentrating on recovering from the hiatus caused by the COVID-19 crisis, and at this time, it would be impractical to try to expand the eligibility for screening.”

“I would say our results indicate that lowering the age range, although not necessarily to 40 but to some age below 50, will be at least worth considering when the current crisis is over,” he added.

Guideline  Recommendations Differ

Breast cancer screening guidelines have generated debate, much of which has focused on the age at which to begin screening.

The US Preventive Services Task Force (USPSTF) and American College of Physicians recommend screening every other year for women on average between the ages of 50 and 74 years.

However, other organizations disagree. The American College of Radiology and Society of Breast Imaging both recommend annual mammograms starting at age 40, and continuing “as long as they are in good health.”

In the UK, where the study was conducted, a national breast cancer screeningprogram offers mammography to women aged 50-70 years every 3 years.

Given the uncertainty that continues to exist over the optimal age for average-risk women to begin screening, the UK Age Trial set out to assess if screening should begin at a younger age and if that might lead to overdiagnosis of breast cancer.