The panel also considered data from a study using computer simulation models to compare expected outcomes of starting and stopping screening at different ages and screening at different intervals. The models suggest that screening average-risk women ages 50 to 74 every two years achieves most of the benefit of annual screening, but with less harm due to factors such as false-positive results, unnecessary biopsies, and “overdiagnosis” of cancers that wouldn’t have progressed or would have not led to the person’s death.
“[The models] only tell us what happens on average in the population. They do not tell us what will happen for an individual woman,” says Jeanne S. Mandelblatt, MD, the lead author of one of the studies commissioned by the USPSTF and a professor of oncology and medicine at Georgetown University’s Lombardi Comprehensive Cancer Center.
For an individual woman, the decision to have a mammogram “is one that she needs to consider with her providers based on her risks and her values for the balance of harms and benefits,” she adds.
But W. Phil Evans, MD, the president of the Society of Breast Imaging, questions the wisdom of biennial screening. “It doesn’t make any sense when you know more cancers can be found in the 50-year-old age group to lengthen the screening time, because the idea is to find the cancer early and to treat it while it’s small, because treatment can be less when the cancer is detected early,” says Dr. Evans, a professor of radiology and the associate vice president for clinical imaging services at the University of Texas Southwestern Medical Center, in Dallas.
“The Society of Breast Imaging and the American College of Radiology are not going to change their guidelines because of this,” he says. “We think it’s very important to begin screening at age 40 and screen yearly thereafter.”
The USPSTF panel did not make recommendations on screening women 75 and older because the current evidence is insufficient to weigh the additional benefits and harms. For the same reason, it did not weigh in on the value of clinical breast examinations, beyond mammography, in women 40 and older or on the value of other imaging techniques, such as digital mammography or magnetic resonance imaging.
However, it did recommend against teaching women how to perform breast self-examination, saying there’s no evidence that it reduces breast cancer deaths.
The critical thing is not to ignore this lifesaving procedure, says Dr. Sledge, who urges all women to discuss mammography with their doctor, beginning at age 40.
“What’s not mentioned in these discussions, but what’s incredibly important, is that in the United States, perhaps as many as even a third of all women just simply don’t follow even the most conservative of screening mammogram recommendations, just as a significant portion of the population doesn’t get screening for colorectal cancer or screening for cervical cancer,” Dr. Sledge notes.
“We could significantly reduce the number of cancer deaths if we applied even the most conservative of screening guidelines,” he says.
Breast cancer is the second-leading cause of cancer death in women, after lung cancer. In 2009, an estimated 254,650 breast cancer cases will be diagnosed, and 40,170 women will die from the disease.
