Lancet: Annual mammography screening starting at 40 does reduce mortality

When it comes to reducing the number of deaths caused by breast cancer, a recently published study suggests, starting screening mammography at age 40 and continuing it yearly does the job and does it well for at least 10 years after the initial exam.

Researchers arrived at this conclusion after following thusly screened women for 17 years.

They drew from the UK Age trial, which is specifically designed to test the widely followed yet hotly contested recommendation of annual screenings starting at 40 for women at average risk for breast cancer.

The study team, whose members are variously based in Britain, the U.S. and Israel, published the findings online July 20 in The Lancet Oncology.

In the Age trial, approximately 161,000 participants were randomly assigned from 1990 to 1997.

The new analysis looks at a control group of 106,953 who received “usual medical care”—screening starting at age 50 and every three years afterward—versus an intervention group of 53,883 invited to receive the annual screenings starting at 40.

After a median follow-up spanning 17.7 years, the authors note, there was a significant reduction in breast cancer mortality in the intervention group compared with the control group in the first 10 years after diagnosis (rate ratio 0·75, 0·58–0·97) from tumors diagnosed during the intervention phase.

Interestingly, the difference did not extend beyond the 10-year mark, and the incidence of breast cancer during 17-year follow-up was similar between the intervention group and the control group.

“Our results support an early reduction in mortality from breast cancer with annual mammography screening in women aged 40 to 49 years,” write the authors, led by Sue Moss, PhD, of the Wolfson Institute of Preventive Medicine in London.

“Synthesis of results from all [relevant] trials, and further data from modern service screening, might clarify long-term effects,” they conclude. “Cumulative incidence figures suggest at worst a small amount of overdiagnosis.”

The conclusion is likely to be scrutinized on that latter score, as its publication comes shortly after a study looking at 16 million women found grounds to declare “widespread overdiagnosis” and a separate, sprawling review of the literature published between fall 2012 and summer 2014 backed up the deduction.