Mammography screening is only part of the answer to breast cancer, a journal commentary says. (Enrique Castro-Mendivil/Reuters)

A 25-year Canadian mammography trial that concluded that the screening does not reduce breast cancer death rates could help shift the focus to prevention, a journal commentary says.

Monday’s online issue of the Annals of Internal Medicine includes two commentaries that discuss the findings of February’s Canadian study as well as a 2013 review of 11 trials on the benefits and harms of breast cancer screening.

Dr. Russell Harris, who studies preventive medicine at the University of North Carolina, said the update of the Canadian National Breast Screening Study offers two messages:

  • Annual mammography did not reduce breast cancer deaths for women aged 40 to 59 compared with women who had (aged 50 to 59) or did not have (aged 40 to 49) clinical breast exams.
  • Overdiagnosis — being diagnosed and presumably treated for breast cancer that would never threaten a patient’s life — is real and makes up at least 22 per cent of cases of invasive breast cancer detected with screening.

"If mammography is really not more than a partial answer to the problem of breast cancer, what further action can women take to deal with a disease that seems unpredictable and uncontrollable? The answer lies in reframing the issue," Harris concludes.

"If we can come to think of screening in a more limited way, moving some of our hope to lifestyle change, we could potentially reduce the harms of screening and gain the multiple benefits of a healthy lifestyle."

For example, women are encouraged to maintain a healthy body weight particularly after menopause and be physically active to reduce the likelihood of being diagnosed with breast cancer.

A second commentary by Swiss researchers published in the same issue was entitled, "It is time to initiate another breast cancer screening trial."

When Dr. Peter Juni of the University of Bern’s Institute of Social and Preventive Medicine analyzed the results of 11 screening trials, he and his team concluded that collectively the analyses do not provide any evidence for an effect of mammography screening on all-cause mortality, which Juni’s team called the most definite measure of the net benefits of mammography. (All-cause mortality is a measure of total death rate without considering specific cause of death that can be used to make comparisons over time.)

Since none of the trials were done in the era of modern breast cancer treatment, Juri argues that the only way to know for sure is to start a new trial with contemporary screening and breast cancer treatments.