Annual Mammograms Do Not Lower Breast Cancer Death Rate
For women turning 40-years-old, they will generally be recommended to get annual mammograms as a preventive measure against breast cancer. The effectiveness of mammography in preventing deaths tied to breast cancer has been debated recently after evidence suggested that this procedure does not help improve mortality rates. Now, in a new long-running study conducted in Canada, researchers once again reported that getting annual mammograms did not reduce the death rate for breast cancer.
For this study, lead researcher Dr. Cornelia Baines, professor emeriti at the University of Toronto's Dalla Lana School of Public Health and fellow researchers examined the data that had been compiled since 1980. The study collected information from 15 screening centers across six provinces in Canada. The researchers divided the female participants into four groups. The groups were first divided into the age groups of 40 to 49-years-old and 50 to 59-years-old. They were then divided into a mammography group, which included an annual exam for five years or a no-mammography group, which involved a physical exam followed by standard care.
Over the next 25 years, the researchers reported that 3,250 women in the mammography group and 3,133 in the no-mammography group were diagnosed with breast cancer. The researchers found that the death rates due to breast cancer were the same regardless of the frequency of the mammograms. The researchers found that 500 died from the mammography group and 505 died in the no-mammography group.
"Mammography detected many more invasive breast cancers," said Baines. "Survival time was longer in women getting mammography. [However], the number of deaths from breast cancer was the same in both groups at 25 years."
The researchers also reported that there were many cases of over-diagnosis in which benign tumors are detected and treated even though treatment would not be necessary.
"It is increasingly being recognized that there are significant harms from screening, and that screening can do much less now than 40 years ago because of improved therapy," Baines added. "Twenty-two percent of the mammography group with screen-detected invasive beast cancer were over-diagnosed and unnecessarily inflicted with therapy."
Breast exam recommendations have varied over the years. In 2009, the United States Preventive Services Task Force revised its recommendations and suggested that women between the ages of 50 and 74 get a mammogram once every two years. For younger women in the age group of 40 to 49, the task force stated that the necessity of an exam should be decided between doctor and patient. Despite these guidelines, the American Cancer Society and the American College of Radiology continue to advise women to get annual mammograms once they turn 40.
"[The study is] an incredibly misleading analysis based on the deeply flawed and widely discredited Canadian National Breast Screening Study," the American College of Radiology stated according to HealthDay.
The study was published in the British Medical Journal.