Mammography detects cancer, but debate rages over when and how often women should get screened.
Women should get screened for breast cancer in their 40s, a study concludes, because they face a greater risk of death when cancers aren't found early.
Women who were diagnosed with cancer in their 40s and died of the disease were more likely to have never had a mammogram than were older women, according to the study.
Seventy percent of the women diagnosed with cancer in their 40s who later died hadn't had a mammogram, compared to 50 percent of women in their 60s. Half of the cancer deaths in the study were in women who had been diagnosed before age 50.
"Breast cancer is primarily a disease of older women, but younger women tend to have faster-growing cancer," says Dr. Barbara Monsees, a professor of women's health and radiology at the Washington University School of Medicine in St. Louis. She wasn't involved in the study.
"There are people who feel that screening doesn't reduce death rates, that it's all in treatment," Monsees tells Shots. "This study corroborates prior studies that screening mammograms save lives."
Breast cancer is much less common in younger women and is most often diagnosed when women are over 60. But in this study, the death rate for women diagnosed in their 40s was almost twice that of women diagnosed in their 70s.
The study is sure to add to the ongoing controversy over when and how often women should get mammograms. It backs up the American Cancer Society's recommendation that women get mammograms every year starting at age 40.
But in 2009, the U.S. Preventive Services Task Force, a federally funded independent panel, recommended that, in general, women should wait until age 50 to start getting mammograms, and then get screened every two years up until age 75.
That recommendation factored in the fact that younger women are more likely to have false positive mammograms, which can lead to unnecessary biopsies and anxiety.
"Overdiagnosis has been completely exaggerated," says Dr. Daniel Kopans, director of breast imaging at Massachusetts General Hospital and an author of the paper. "Well, calling people back for additional screening causes anxiety, I understand that. But it absolutely saves lives. You reduce the death rate by 30, 40 percent if you start screening at age 40."
This study looked at women in the Partners HealthCare system in Boston who were diagnosed with invasive breast cancer from 1990 to 1999. The researchers then checked the women's medical records to see if and when they'd had mammograms.
It's a form of study called a "failure analysis," a what-went-wrong approach similar to that used in investigating airplane crashes. Dr. Blake Cady, an emeritus professor at Brown University's Alpert Medical School and one of the study authors, tells Shots that he thinks it better reflects the effect of screening than do population-based studies because the health system records show which women actually got mammograms, rather than say they did.
Of the 7,301 women in the study, 609 had died of breast cancer by 2007. Almost three-quarters of the women who died hadn't had a mammogram in the two years before the cancer was found.
Overall, 80 percent of the women were getting mammograms at least every two years, well above the national average. Some of them still got breast cancer, but, overall, the death rates were higher in women whose tumors weren't found until they could be felt.
"While the analysis reveals that regular screening will not prevent all breast cancer deaths," Robert Smith, director of screening for the American Cancer Society, told Shots in an email, "it also reveals that even with improvements in treatment there is still a significant advantage of detecting breast cancer with mammography before symptoms develop."
This new study also found no benefit in mammograms for women over age 69 when it came to reducing cancer death risk.
The study was published online in the journal Cancer.