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The American Cancer Society still recommends women begin getting yearly mammograms when they turn 40, even though a physician's group has just released differing guidelines.

The American College of Physicians (ACP) says women in their 40s should talk with their doctors about their risk for breast cancer, and the pros and cons of mammograms, before deciding whether to get screened.

Mammograms are breast x-rays that can often find tumors when they are small, before they can be felt by hand. The earlier breast cancer is found, and the smaller the tumor, the easier it is to treat and the better a woman's chances of survival. Breast cancer is the most common cancer among women (other than non-melanoma skin cancer). An estimated 178,480 women will develop the disease in 2007, with 40,460 women expected to die from it. Although most breast cancers are found in women age 50 or older, about 17% of invasive breast cancers occur in women in their 40s.

"In our view, the evidence doesn't support a blanket recommendation for women in this age group," says Douglas K. Owens, MD, MS, chair of the physician's group committee that developed the guidelines. "There are important benefits to screening mammography, but we believe the decision to be screened should be based on an informed conversation between a patient and her physician," says Owens, a professor of medicine at Stanford University School of Medicine and a researcher with the Veterans Affairs Palo Alto Health Care System, both in Palo Alto, Calif.

The American Cancer Society's director of cancer screening, Robert Smith, PhD, says there's plenty of evidence mammograms save lives, even for younger women.

"The American Cancer Society and other organizations have endorsed mammography screening for women in their 40s because direct and inferential evidence supports its value in reducing morbidity [injuries] and mortality [deaths] from breast cancer, the second leading cause of cancer death in women," he says.

Other groups that recommend mammograms every 1 or 2 years for women in their 40s include the US Preventive Services Task Force and the American College of Obstetricians and Gynecologists.

The ACP guideline says mammograms can reduce breast cancer deaths by about 15% among women in their 40s. But Smith says newer studies indicate the benefit is much greater -- 40% or more.

The ACP guideline is published in the most recent issue of Annals of Internal Medicine. It emphasizes discussing a woman's individual risk of breast cancer when deciding whether she should get screened. But predicting breast cancer risk for any one woman can be tricky; an editorial published along with the new guidelines acknowledges that such predictions are "extremely inexact."

"While such factors as family history of breast cancer, breast density, and genetic mutations may help identify women at increased risk, most women with diagnosed breast cancer have none of these risk factors," write the University of Washington's Joann Elmore, MD, MPH, and John Choe, MD, MPH, in the editorial.

That fact is key, says Smith.

"If we were to screen only those women in their forties who had significant, known risk factors, we would fail to detect the majority of breast cancers that arise during that decade of life," he points out.

The ACP guideline also says doctors should discuss with women the "benefits and potential harms" of mammography.

The most important benefit, of course, is the drop in breast cancer deaths. The potential harms include pain from the procedure, a small amount of radiation exposure, and the anxiety and fear that can result when a mammogram detects something suspicious that turns out not to be cancer -- a so-called false-positive finding.

Guideline committee chair Owens acknowledges that the benefit of mammograms will probably outweigh other concerns for most women in their 40s.

"We still think many women will choose to get mammography, and we're supportive of that," he says. "The most important thing is that women be well-informed about the decision they're making."

Smith agrees that women should be given the facts about mammography. It's not a perfect test. Sometimes mammograms miss tumors, and sometimes they give false-positive results.

But he worries that the ACP guidelines will cause some women to skip these lifesaving tests.

"It would be a major public health setback if these new guidelines caused some women and their doctors to conclude that screening can safely be postponed," he says.

Citation: "Screening Mammography for Women 40-49 Years of Age: A Clinical Practice Guideline from the American College of Physicians." Published in the April 3, 2007, Annals of Internal Medicine (Vol. 146, No. 7: 511-515). First author: Amir Qaseem, MD, PhD, MHA, American College of Physicians.

"Breast Cancer Screening for Women in Their 40s: Moving from Controversy about Data to Helping Individual Women." Published in the April 3, 2007, Annals of Internal Medicine (Vol. 146, No. 7: 529-531). First author: Joann G. Elmore, MD, MPH, Univeristy of Washington.