Health: An Expert's Advice on Mammograms
Dr. David C. Grossman, senior investigator at Seattle’s Group Health Research Institute, has served nearly three years of a four-year term as one of 16 members on the U.S. Preventive Services Task Force, which last year was at the center of a controversy arising from its new recommendations on mammography screenings. News reports have indicated that some states stopped offering routine mammograms for uninsured women in their 40s as a result of the task force’s recommendations. That has not happened in Washington, and Dr. Grossman says he has not seen any local statistics on how the recommendations have affected the number of screening mammographies being performed. He took part in this interview as a U.S. Preventive Services Task Force member, not as a Group Health doctor, and the recommendations of the task force do not necessarily reflect Group Health’s positions.
Seattle magazine: The U.S. Preventive Services Task Force’s breast cancer screening recommendations elicited a firestorm of criticism last November from cancer-support groups, radiologists and other medical experts. Did the fallout surprise you or other task force members?
Dr. Grossman: The interest and media attention didn’t surprise us. For decades, a controversial debate has focused on how well mammograms work as a routine screening test for breast cancer in women ages 40 to 49. What surprised us was how widely we were misunderstood by the public and the media. We should have worded and communicated the recommendations better.
SM: Please reiterate the task force’s 2009 breast cancer screening recommendations.
DG: We recommend that doctors discuss the benefits and harms of mammography with their female patients, starting at age 40, so each woman can make an informed and personal decision about when to start screening mammograms. For women [who are] at average risk, routine breast cancer screening should begin no later than age 50. Average-risk women should be screened routinely every two years from ages 50 to 74. We used to say to age 69, but we found evidence to support screening to 74 for average-risk women.
SM: How did you arrive at the 2009 recommendations?
DG: It’s a well-defined, transparent process. We work with researchers from the Oregon Evidence-based Practice Center—a partnership of Oregon Health & Science University, the Portland Veterans Affairs Medical Center and Kaiser Permanente Center for Health Research. They do a comprehensive scientific literature review. We also commissioned two new studies. A small subgroup of the task force analyzed all the information and drafted recommendations for the full task force to consider.
SM: What puts some women at higher risk than others?
DG: Genetics, such as carrying the BRCA1 or BRCA2 gene; a strong family history of early breast or ovarian cancer; and chest radiation therapy from Hodgkin’s lymphoma. Other than genetics, the most important risk factor is age. Women have a dramatically higher risk of breast cancer in their 60s than in their 40s.
SM: Why do younger women have the highest rates of false positives?
DG: Their true positives are much rarer, and their breasts are denser, making their mammograms harder to “read.”
SM: What about the recommendation concerning monthly breast self-exams?
DG: This [recommendation] was also widely misunderstood. The task force never suggested that women not do breast self-exams. We recommended against having doctors teach all women how to do them. That was based on two big international studies showing no benefit from health care workers teaching women how to do breast self-exams.
SM: Have the recommendations been changed because of the uproar?
DG: No. The November 2009 recommendations have had no substantive changes. But the wording of the recommendation about routine screening for 40- to 49-year-old women was changed to be clearer. It had been misunderstood as the task force’s recommending against screening in this age group. The task force agrees that mammography offers benefits to women ages 40 to 49. But some harms [from overdiagnosis and false positives] are also associated with it, including unneeded biopsies, radiation, surgery, chemotherapy—and anxiety over false positives. What got lost in the message was that there is a balance between benefits and potential harms—and women need to be informed. Earlier, no one had talked about the harms.
SM: Some call the recommendations a disservice to women. How do you respond?
DG: In the 40- to 49-year-old group, the benefits versus harms of mammography are a close call, and it’s important that women be informed and involved in decisions about their own health. Whatever decision any woman makes, after discussing it with her doctor, is the right decision.
SM: Despite the criticism, some patient advocacy groups, such as the National Breast Cancer Coalition, praise the shift. Why?
DG: Some groups have concerns about harms from mammographic screening. Some other groups put greater weight on the benefits. No one disagrees that screening mammography offers a benefit, but not everyone weighs the harms in the same way. Remember: Benefit minus harm equals net benefit.
SM: How do you defend the recommendations to women in their 20s, 30s and 40s who have breast cancer?
DG: Breast cancer can be a devastating disease, particularly in young women. We all want to figure out how to prevent that. But we must recognize the limits of our current technologies and systems, including mammography. We could start routine screening at 15, but that would cause more harm than good. The health care community can do a better job identifying women at very high risk, through taking careful family histories and referring them to genetic counselors for advice on special preventive measures, including earlier screening.
SM: Please explain your November 2009 statement (published in The Seattle Times): “A major issue with breast cancer is overdiagnosis.”
DG: No one in the scientific community doubts whether overdiagnosis exists; the question is how common it is. Overdiagnosis is a potential problem when you test for early forms of disease. In cancer, it means detecting a small lesion that would never cause any symptoms or health problems during a person’s lifetime. It may never have become invasive, and it might even disappear. We don’t always know which noninvasive cancers we find will ultimately harm a person. That can lead to overtreatment with surgery, radiation or chemotherapy. The public may overestimate screening mammography’s accuracy and effectiveness in finding invasive breast cancer. In women ages 39 to 49, mammography reduces death from breast cancer by about 15 percent. That means preventing one cancer death for every 1,904 women screened routinely over a decade. It’s good to prevent one death, but we need a more accurate screening method. Much research is ongoing to address this.
SM: How often are recommendations for breast cancer screening revisited?
DG: For 26 years, the task force has issued many recommendations about various preventive services, including breast cancer screening. We routinely revisit each recommendation every five years—more often with compelling new evidence.
SM: What’s the biggest lesson learned from the fallout?
DG: We must word recommendations so not only doctors, but also the public, understand them.
Published in October 2010