A new study conducted by researchers at the National Institutes of Health and their collaborators has found that women who have been diagnosed with and treated for breast cancer age biologically more quickly than women who do not have the disease.

Breast cancer patients who underwent radiation therapy had a stronger correlation with biological ageing than those who underwent surgery. This data implies that the ageing effect is not accelerated by cancer development.

“Of the three treatment classes we looked at, radiation therapy had the strongest associations with the biologic age measures assessed in the study,” said Jack Taylor, M.D., PhD, the senior author of the paper who is an Emeritus Scientist at NIEHS.

“The increases can be detected years after treatment.” Biological age reflects a person’s cell and tissue health, which differs from chronological age.

To measure biological age, the researchers studied 417 women who had blood samples collected at two-time points about eight years apart. About half of the women studied were selected because they had developed breast cancer during that time span.

The participants are enrolled in the Sister Study, a research effort that seeks to identify environmental risk factors for breast cancer risk and other health conditions, led by the National Institute of Environmental Health Sciences (NIEHS), part of NIH.

The researchers used three different established “methylation clocks” to determine if there were changes in a woman’s biological age between the two-time points.

The clocks measure naturally occurring, chemical modifications to a person’s DNA, known as methylation changes. Small variations in methylation patterns can help determine a person’s risk of developing an age-related disease.

Women diagnosed with breast cancer had faster ageing rates by all three clocks, with no significant differences, when compared to women who did not develop breast cancer.

Next, the scientists examined whether biological age was associated with specific treatment regimens, such as surgery, chemotherapy, radiation therapy, and endocrine therapy. Among women with breast cancer, ageing rates varied by treatment type.

“Radiation is a valuable treatment option for breast cancer, and we don’t yet know why it was most strongly associated with biological age,” noted Dale Sandler, PhD, chief of the NIEHS Epidemiology Branch and a co-author of the paper.

“This finding supports efforts to minimise radiation exposures when possible and to find ways to mitigate adverse health effects among the approximately 4 million breast cancer survivors living in the United States.”

The scientists emphasised that women should not abandon radiation therapy as an option based on this research. Current breast cancer treatments that include radiation are very effective in preventing breast cancer from spreading.

“Women faced with a breast cancer diagnosis, should discuss all possible treatment options with their doctors to determine the best course of treatment for them,” said Katie O’Brien, PhD, a scientist in the NIEHS Epidemiology Branch and a co-author of the paper.