Routine breast screening with mammograms packs a less-than-expected effect on preventing cancer deaths, according to a study by Norwegian researchers that once again sparks a fierce debate over its value.
Published this past week in the New England Journal of Medicine, the study takes into account data from 40,075 women and tracks the reduction in cancer deaths as a screening program was expanded throughout Norway, beginning in 1996. It also coincided with improved treatment for patients. The study’s authors concluded that inviting women in ages 50 to 69 to undergo routine mammograms and offering them better care from a team of experts helped cut their breast cancer death rate by 10%. However, they noted that the death rate in women over 70—a group that also received better care but was not urged to have mammograms—decreased by 8%, indicating that the mammograms only produced a slight benefit. Moreover, researchers stated, the rate of reduction in mortality with mammograms fell far short of the 30% they had anticipated before undertaking the study.
In a commentary published alongside the study, Gilbert Welch, MD, of Dartmouth Medical School in Hanover, New Hampshire, stated that based on the findings, screening mammograms may yield a mere 2% benefit in cutting breast cancer deaths. He said the new results show that for every 2,500 women age 50 who receive a mammogram, only one will avoid dying of breast cancer and as many as 1,000 will be informed that doctors have seen something suspicious. About 500 of these patients will undergo a biopsy, with five to 15 women subsequently subjected to unnecessary treatment for a condition that would never truly “bother” them, Welch wrote.
Not surprisingly, the American College of Radiology (ACR) questioned the validity of the research. “This article suggests that most of the decrease in breast cancer deaths is due to improvements in therapy with a lesser contribution from screening,” Daniel Kopans, MD, a member of the ACR’S Breast Imaging Commission and an affiliate of Massachusetts General Hospital in Boston, Mass., said in a statement.
“There are large, published studies from Sweden and the Netherlands that show that most of the decrease in deaths is actually due to screening and not therapy.”
Kopans deemed the average 2.2 year follow-up of study subjects “too short”, as well as likely accountable for the new results. “The full impact of screening would not be expected so soon,” he said, adding that the women in the study were screened every two years. By contrast, Kopans observed, women in the U.S. have been encouraged to seek annual mammograms, thereby giving malignancies less time to grow between screenings.
“The authors confirm that screening saves lives,“ Kopans stated in summarizing the ACR’s reaction to the study. “It has now become a debate of degree. Therapy is only successful when cancers are found earlier. (The researchers’) very short follow-up, without being certain that they did not dilute the benefit with cancers diagnosed before actual screening, and without knowing the actual contamination of the ‘unscreened’ women, makes these results, at best, premature.
“Would the authors, and Welch suggest that it is not worthwhile if we only decrease deaths by 30%? There is no universal cure in sight. Until one is found, annual screening and early detection, beginning by the age of 40, offer women the best chance for cure.”