One of the most respected and influential groups in the continuing breast-cancer screening debate said Tuesday that women should begin mammograms later and have them less frequently than it had long advocated.
The American Cancer Society, which has for years taken the most aggressive approach to screening, issued new guidelines on Tuesday, recommending that women with an average risk of breast cancer start having mammograms at 45 and continue once a year until 54, then every other year for as long as they are healthy and expected to live another 10 years.
The organization also said it no longer recommended clinical breast exams, in which doctors or nurses feel for lumps, for women of any age who have had no symptoms of abnormality in the breasts.
Previously, the society recommended mammograms and clinical breast exams every year, starting at 40.
The changes reflect increasing evidence that mammography is imperfect, that it is less useful in younger women, and that it has serious drawbacks, like false-positive results that lead to additional testing, including biopsies.
But the organization's shift seems unlikely to settle the issue. Some other influential groups recommend earlier and more frequent screening than the cancer society now does, and some recommend less, leaving women and their doctors to sort through the conflicting messages and to figure out what makes the most sense for their circumstances.
In fact, although the new guidelines may seem to differ markedly from the old ones, the American Cancer Society carefully tempered its language to leave plenty of room for women's preferences. Although it no longer recommends mammograms for women ages 40 to 44, it said those women should still "have the opportunity" to have the test if they choose to, and that women 55 and older should be able to keep having mammograms once a year.
This year, 231,840 new cases of invasive breast cancer and 40,290 deaths are expected in the United States.
The new guidelines were published Tuesday in the Journal of the American Medical Association, along with an editorial and an article on the benefits and risks of screening, which provided evidence for the guidelines. A separate article and editorial on the subject were also published in another journal, JAMA Oncology.
The guidelines apply only to women at average risk for breast cancer — those with no personal history of the disease or known risk factors based on genetic mutations, family history or other medical problems.
The changed policy resulted from an exhaustive review of research data, which the cancer society conducts regularly to update its screening guidelines, said Dr. Richard C. Wender, the organization's chief cancer control officer. The last review was in 2003, and this one took about two years.
Wender said he hoped the new guidelines would end some of the debate and confusion about mammography. But some doubted that the guidelines would bring clarity.
"I think it has the potential to create a lot of confusion amongst women and primary care providers," said Dr. Therese B. Bevers, the medical director of the Cancer Prevention Center at the University of Texas M. D. Anderson Cancer Center in Houston.
Dr. Nancy L. Keating, a professor of health care policy and medicine at Harvard and a co-author of the JAMA editorial about the guidelines, said she thought the new advice had been thoughtfully developed and was headed in the right direction. Keating, who practices at Brigham and Women's Hospital in Boston, said doctors and patients had clung to the practice of early and yearly mammograms out of fear that they would otherwise miss detecting a cancer.
The National Comprehensive Cancer Network, an alliance of prominent cancer centers, recommends mammograms every year starting at age 40. The American College of Obstetricians and Gynecologists recommends them every year or two from ages 40 to 49, and every year after that. It also recommends yearly clinical breast exams starting at age 19.
The obstetricians' group said it was convening a conference in January, with the participation of the American Cancer Society, the comprehensive cancer network and other organizations, to try to develop a consistent set of guidelines.
Among those invited are the U.S. Preventive Services Task Force, which recommends less testing: mammograms every other year for women ages 50 to 74. In 2009, it advised against routine mammograms for women ages 40 to 49, a decision that ignited a firestorm of protests from doctors, patients and advocacy groups.
The task force, an independent panel of experts appointed by the Department of Health and Human Services, softened its approach in draft guidelines that were posted on its website in April and have yet to be finalized. Instead of advising against routine screening for women in their 40s, the group now says, "The decision to start screening mammography in women before age 50 years should be an individual one."
But the task force gave the evidence for screening women under 50 a rating of "C," reflecting its belief that the benefit is small. Services with a C rating do not have to be covered by the Affordable Care Act, according to the Department of Health and Human Services — a serious worry for advocates.
In response to the new cancer society guidelines, the task force issued a statement saying it would "examine the evidence" the cancer society had developed and reviewed before finalizing its recommendations. The statement also noted that the task force recognized "that there are health benefits to beginning mammography screening for women in their 40s."
In making recommendations about screening, experts try to balance the benefits of a test against its harms for women in various age groups. A general explanation of the reasoning behind the new guidelines is that breast cancer is not common enough in women under 45 to make mammograms worthwhile for that age group but that the risk of the disease increases enough to justify screening once a year after that. Specifically, the risk of developing breast cancer during the next five years is 0.6 percent in women ages 40 to 44; 0.9 percent from 45 to 49; and 1.1 percent from 50 to 54.
The risk keeps increasing slowly with age, but by 55, when most women have passed through menopause, tumors are less likely to be fast-growing or aggressive, and breast tissue changes in ways that make mammograms easier to read — so screening every other year is considered enough.
As for the decision to stop recommending clinical breast exams, the society said that there was no evidence that the exams save lives, but that there was evidence that they could cause false positives — meaning they could mistakenly suggest problems where none existed and lead to more tests. The exams can take 5 or 6 minutes that could be put to better use during office visits, said Dr. Kevin C. Oeffinger, the chairman of the cancer-society subgroup that developed the guidelines and director of cancer survivorship at Memorial Sloan Kettering Cancer Center in New York.
According to the evidence review accompanying the guidelines, the benefit of regular mammography is that it can reduce the risk of dying from breast cancer by about 20 percent. Because breast cancer is less common in younger women, their baseline risk of dying is lower, and screening them saves fewer lives.
While younger women have less to gain from mammograms, the cancer society found, they incur all the potential harms. One harm is false positives, which can lead to more tests, including biopsies. A 2011 study cited in the article explaining the new guidelines found that 61 percent of women who had yearly mammograms starting at age 40 had at least one false positive by the time they were 50. Being tested every other year instead of every year can cut the false positive rate significantly, the JAMA Oncology article explaining the guidelines said, to about 42 percent from 61 percent.
Some women consider false positives a small price to pay for the chance of identifying a cancer early. Others find being called back for more tests too nerve-racking.
Another potential risk of mammography is overdiagnosis, meaning that some of the tiny cancers it finds might never progress or threaten the patient's life. But because there is now no way to be sure which will turn dangerous, they are treated anyway.
There are no widely accepted figures on how often overdiagnosis occurs. Researchers think that it is mostly likely in women found to have ductal carcinoma in situ, or DCIS, tiny growths in the milk ducts that may or may not evolve into invasive cancer. About 60,000 cases of DCIS are diagnosed in the United States each year.
"We would all love to avoid diagnosing and treating a breast cancer that doesn't need treatment," Oeffinger said. "But we don't have the tools."
But, he added: "This area is rapidly changing. In five to seven years, we'll have more knowledge in this area that will let us be more personalized in our approach."
Keating said, "Radiologists are working hard to find new and better screening tests, which we desperately need, but I think it will take time."