It’s well-established that women who receive mammograms to screen for breast cancer reduce their risk of dying from the disease, but when to start that screening has long been controversial with guidelines varying by country.

In the US, for example, the American Cancer Society (ACS) recommends that women receive mammograms to screen for breast cancer starting at age 45, while guidelines from the US Preventive Services Task Force, an independent panel of national experts in disease prevention and evidence-based medicine, advises women to begin screening at age 50. Both groups say that women should have the option to start breast cancer screening at age 40 with yearly or biennial mammograms, depending on their personal risk factors.

In the UK, as well as many other countries, breast cancer screening is offered to women ages 50 to 70 every three years. The thinking behind this and other such recommendations is that screening with mammograms before age 50 will find more tumors that turn out to be benign, and the risk for overtreatment, with biopsies and other testing, will outweigh the benefits of screening.

Recent development: To further investigate the validity of the UK’s breast cancer screening recommendation, researchers at Queen Mary University of London conducted a 23-year study to see how women fared when they began receiving mammograms at age 40 versus age 50.

To begin the study, which was recently published in The Lancet Oncology, researchers randomly assigned nearly 60,000 women to a study group that started receiving yearly mammograms at age 40. More than 100,000 women were assigned to a control group that would wait until age 50 to begin standard breast cancer screening with mammograms every three years.

Study findings: After the first 10 years of the study, 83 women in the study group had died from breast cancer compared with 219 deaths from the disease in the control group. This translates into a 25% reduced risk of dying from breast cancer when screening started at age 40 instead of age 50.

After the first 10 years of the study, the women who had started their breast cancer screening earlier adopted the same standard mammography screening schedule that the control group followed. During this part of the study, however, both groups had roughly the same risk of dying from breast cancer.

Takeaway: Based on these findings, the researchers conclude that the benefits of starting mammograms at age 40 outweigh the risks of overtreatment. They also note that the benefits may now be even greater than those shown in the research due to improvements in mammogram technology since the study began.

Some well-respected medical institutions in the US, such as the Mayo Clinic in Rochester, Minnesota, do recommend starting mammogram screening at age 40. This study suggests that lowering all official guidelines to age 40 could save lives.

Important: Women should discuss their breast cancer screening schedule with their doctors to ensure that they are doing all they can to help protect themselves against the disease.

Source: Study titled “Effect of Mammographic Screening from Age 40 Years on Breast Cancer Mortality (UK Age Trial): Final Results of a Randomized, Controlled Trial,” led by researchers at Queen Mary University of London, published in The Lancet Oncology.