Nobody enjoys getting a mammogram, but it is an essential prevention measure against breast cancer deaths. Some experts, however, are questioning how often women really needmammograms to detect cancer and ultimately save lives.
Most women are used to hearing that they should get a mammogram every year starting at age 40. The U.S. Preventive Services Task Force in April issued a draft of mammography recommendations that greatly reduces that frequency, saying evidence to support annual mammograms for women in their 40s is weak. The USPSTF recommends women get mammograms every two years once they turn 50.
The USPSTF is a panel of independent experts that advises Congress, and should its guidelines be adopted, insurers would no longer be required to cover annual mammograms unless Congress mandates they do so. Since releasing the draft of recommendations, several groups have called the guidelines into question.
The American College of Radiology is one such group, standing firm on yearly mammographystarting at 40. "Every major group with expertise in breast cancer care and the USPSTF agree that annual mammography saves the most lives," says Dr. Debra Monticciolo, chair of the ACR's Breast Imaging Commission. "From a woman's perspective, this is the most important reason to have a mammogram -- to decrease the chance that she will die of breast cancer."
Screening mammography became widespread in the mid-1980s, Monticciolo says. According to National Cancer Institute data, the five-year survival rate of breast cancer was 78.4 percent in 1985. In 2007 it was 91 percent, an increase that is credited to annual screening mammography by experts like Monticciolo.
According to Monticciolo, the USPSTF has "no breast cancer experts on their panel -- not one. This is a major failing of the task force." She goes on to say the task force claims to be eliminating bias "but what they have eliminated is knowledge." Even though the panel consists of medical experts, breast imaging experts are the best to assess breast imaging studies, she adds.
"I wouldn't presume to review a brain study and give neurology guidance," Monticciolo says. "Without proper expertise, they have been unable to accurately and completely assess the scientific literature."
The New Analysis
To be clear, the USPSTF's new guidelines don't recommend against annual screening mammography for women in their 40s. "It's clear that the value of mammography increases with age," says Dr. Kirsten Bibbins-Domingo, vice chair of the U.S. Preventive Services Task Force. "But women between the ages of 50 and 74 are the most likely to achieve the benefits of mammography with the fewest harms," she adds, saying that screening visits every other year will still yield the same benefits.
That's for most women -- those with an average risk of developing cancer. "The decision to start screening mammography in women prior to age 50 years should be an individual one," reads the draft. The expert panel also found adequate evidence that annual mammography results "in harms for women aged 40 to 74." Those harms include stress and psychological strife from extra procedures due to false positives, such as biopsies or more imaging studies. The USPSTF says false positives are "common" in mammography.
"Our goal is to give women and their doctors advice for what frequency gives you the greatest chance of preventing death by breast cancer, while keeping negative effects and false positives minimal," Bibbins-Domingo says. Women who are at a higher risk of breast cancer, including those with a strong family history, should consult with their doctors about more frequent screening, the USPSTF advises.
You'd be forgiven for thinking that exposure to radiation is also one of the main harms, but it isn't. According to the American Association of Physicists in Medicine, dosages of radiation below 50 to 100 mSv are "too low to be detectable and may be nonexistent." An average bilateral mammogram delivers only 0.5 mSv, or 1 percent of the minimum dosage for risk.
One of the dangers outlined in the task force's analysis is the sticky subject of overdiagnosis. "Some mammograms are going to detect a cancer that wouldn't have caused a problem for a woman in her lifetime," Bibbins-Domingo says. For example, a cancerous tissue detected by mammography that never would have spread, or at least not before something else took the patient's life first.
"If that cancer is treated, then you have all the harms that come along with overtreatment," Bibbins-Domingo says. That includes the often devastating side effects of chemotherapy, which is also expensive at an average of $80,000 to $100,000 a year.
Since it's often difficult to predict the impact of cancer down the road, the prudent thing to do istreat it, or so many believe. "When we're screening, we're looking for very early stage cancer," Monticciolo says, and the earlier cancer is detected, the better survival rates are.
Trying to estimate the percentage of cases that are overdiagnosed, or present no harm, is difficult without a crystal ball. The USPSTF calculated a rate of 19 percent -- that is 19 percent of breast cancer cases posed no threat, but it notes that some literature suggests a rate as high as 54 percent.
Monticciolo says that estimate is "markedly exaggerated, which a proper assessment of the literature will uncover." According to the International Agency for Research on Cancer, overdiagnosis is somewhere in the 1 to 10 percent range, with a summary estimate of 6.5 percent. The ACR agrees with that number based on its evaluation of the evidence, Monticciolo says.
Despite that lower estimate, the agency agreed with the USPSTF that evidence that annual mammograms reduce mortality for women in their 40s is "limited." The IARC is part of the World Health Organization, which released the same findings in 2002.
The USPSTF draft was open to public comment until May 18. After the panel carefully reviewed public comment, according to its websites, it is in the process of finalizing the recommendations. Once the final recommendations are released, many women could lose annual screening mammography coverage because the Affordable Care Act uses USPSTF guidelines to determine qualifying preventive care, according to the ACR.
There is one thing all experts agree on: Breast cancer is a highly individual disease, influenced by genes, family history and unknown factors. Talking with your doctor openly about the risks and benefits of mammography is the best guidance you can get, and annual exams are still covered as free preventive care -- for now. "Women should always be aware of their bodies, and changes in their bodies," Bibbins-Domingo says. And if something changes, make an appointment.