So should women over the age of 40 get an annual mammogram to guard against breast cancer? Or should these tests be focused more on women who have a higher risk of breast cancer? A new study published in The New England Journal of Medicine suggests the latter approach.
In this study, Dr. H. Gilbert Welch, who is an epidemiology and biostatistics professor at Dartmouth College’s Geisel School of Medicine, and Dr. Archie Bleyer, an oncologist and clinical research professor at Oregon Health and Science University and professor of pediatrics at the University of Texas Medical School, looked at data collected by the National Cancer Institute and the Centers for Disease Control and Prevention from 1976 through 2008. The pair identified trends in early-stage breast cancer and late-stage breast cancer diagnosed in women who were 40 years old and above.
The researchers noted that mammography has resulted in the doubling in the number of early-stage breast cancers diagnosed annually. That number changed from 112 cases to 234 cases per 100,000 women. However, the number of women with late-stage cancer actually decreased by 8 percent, from 102 to 94 cases per 100,000 women. “With the assumption of a constant underlying disease burden, only 8 of the 122 additional early-stage cancers diagnosed were expected to progress to advanced disease,” they stated. Furthermore, the researchers estimated that mammograms caused 1.3 million U.S. women to be over-diagnosed during the past three decades. Their analysis estimated that breast cancer was over-diagnosed in more than 70,000 women in 2008 alone; this number accounted for 31 percent of all breast cancers that were diagnosed that year.
In their conclusion, the coauthors write, “Despite substantial increases in the number of cases of early-stage breast cancer detected, screening mammography has only marginally reduced the rate at which women present with advanced cancer. Although it is not certain which women have been affected, the imbalance suggests that there is substantial overdiagnosis, accounting for nearly a third of all newly diagnosed breast cancers, and that screening is having, at best, only a small effect on the rate of death from breast cancer.”
The publication of this study has resulted in some backlash. The Washington Post points out that the American Cancer Society believes the study “must be viewed with caution” while the American College of Radiology questioned the study’s validity. Furthermore, Los Angeles Times reporter Monte Morin talked to Dr. Stephen Feig, the president of the American Society of Breast Disease as well as a radiologist at the University of California Irvine, who described the study as scientifically weak.
And what do women think on this? A non-scientific poll of Los Angeles Times readers put it almost at an even split – 49 percent said yes, the findings would influence their decision on getting a mammogram while 51 percent said the study would not influence their decision to get a mammogram.
So is this a study worth paying attention to? I’d suggest that you talk to your doctor about what recommended schedule is best for you. With that said, I can definitely see Dr. Welch’s point when he told the Los Angeles Times that he thinks women should be aware of the problems with mammography and that screenings should be conducted based on risk instead of annual screenings based on age. “It's women at the highest risk of dying from breast cancer that stand to benefit the most from screening, and they're the least likely to be overdiagnosed,” he stated, adding that women who develop symptoms of breast cancer should definitely get a mammogram.
Primary Sources for This Sharepost:
Aizenman, N. C. (2012). Mammograms leading to unnecessary treatment, study finds. Washington Post.
Blyer, A. & Welch, H. G. (2012) Effect of three decades of screening mammography on breast-cancer incidence. New England Journal of Medicine.
Morin, M. (2012). Study questions value of mammography screening. Los Angeles Times.
Published On: November 23, 2012