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New government guidelines recommending that women start screening for breast cancer at age 50 instead of 40 set off a round of criticism this week and caused much confusion for women who for years have been told that early detection saves lives.

But a number of women’s health organizations, including Our Bodies Ourselves, the National Women’s Health Network and Breast Cancer Action, for years have warned that regular mammograms do not necessarily decrease a women’s risk of death. Premenopausal women in particular are urged to consider the risks and benefits.

In fact, the NWHN issued a position paper in 1993 recommending against screening mammography for pre-menopausal women. It was a very controversial position at the time — even more so than now. The breast cancer advocacy movement was in its infancy and efforts were focused on getting Medicare and insurance companies to cover mammograms. What the NWHN found — and other groups have since concurred — is that the potential harm from screening can outweigh the benefits for premenopausal women.

That statement is tricky, and based on the poor explanations I’ve seen that fail to specifically address the potential dangers, it’s no wonder women are frustrated. Some are even questioning whether the guidelines were unveiled as a cost-cutting measure — a sign of the “rationing” to come under health care reform. In addition to delaying routine screening until age 50, the guidelines recommend screening women between the age of 50 and 74 every two years. It’s important to keep in mind this is intended for women with no known risk factors; women in high-risk groups should start earlier, and it may be prudent to schedule more frequent mammograms.

Adding to the confusion, cancer groups are split. The American Cancer Society came out strongly against the new guidelines. The National Cancer Institute, meanwhile, said it would reconsider its own recommendations in light of new studies. Some doctors said they would proceed cautiously before revising screening advice for patients.

I don’t believe the new guidelines are politically motivated, nor are they “patronizing” to women simply because they call into question the stress related to biopsies and false positive results. Rather, the guidelines provide a useful framework for helping each of us to decide when is the best time to begin screenings and the intervals at which they should be repeated.

The guidelines are in sync with international recommendations; the World Health Organization recommends starting screening at age 50, and in Europe, mammograms are given to post-menopausal women every other year and detection rates are similar to the United States. During an interview on MSNBC on Tuesday, breast cancer expert Dr. Susan Love said the government’s guidelines bring us into line with the rest of the world and with current research. (Read more at her blog.)

You might be thinking: Wait a moment, isn’t earlier better? Why would delaying detection be in my best interest? I’m going to explain why, but let’s first take a closer look at the guidelines, which were released by the U.S. Preventative Services Task Force (USPSTF), an independent panel of experts in prevention and primary care. (The task force operates under the Agency for Healthcare Research and Quality, the research arm of the U.S. Department of Health and Human Services.)

The guidelines are an update of the 2002 USPSTF recommendation statement, which called for mammograms every one to two years, starting at age 40. Dr. Alfred Berg of the University of Washington, who chaired the task force in 2002, told The New York Times this week, “We pointed out that the benefit will be quite small.” He added that while older women experience the most benefits from the screening, mammograms still prevent only a small percentage of breast cancer deaths.

Breast cancer is the second-leading cause of cancer-related deaths in women (lung cancer is number one). According to the National Cancer Institute, about 192,370 women will be diagnosed with breast cancer in 2009, and 40,170 women will die of the disease this year. A woman who is now 40 years old has a 1.44 percent chance of being diagnosed with breast cancer over the next 10 years.

For the 2009 update, the panel, now with different members, examined the role of five screening methods in reducing breast cancer mortality rates: film mammography, clinical breast examination, breast self-examination, digital mammography, and magnetic resonance imaging. It also commissioned two studies:

1.) A targeted systematic evidence review of six selected questions relating to benefits and harms of screening.

2.) A decision analysis that used population modeling techniques to compare the expected health outcomes and resource requirements of starting and ending mammography screening at different ages and using annual versus biennial screening intervals.

Here is the summary of the task force’s findings, published in the Annals of Internal Medicine. The grades are explained here; A is the highest recommendation (meaning there’s a high certainty the benefits are substantial), and D is the lowest. A rating of I indicates evidence is insufficient or conflicting.

The USPSTF recommends against routine screening mammography in women aged 40 to 49 years. The decision to start regular, biennial screening mammography before the age of 50 years should be an individual one and take patient context into account, including the patient’s values regarding specific benefits and harms. This is a C recommendation. The USPSTF recommends biennial screening mammography for women aged 50 to 74 years. This is a B recommendation. The USPSTF concludes that the current evidence is insufficient to assess the additional benefits and harms of screening mammography in women 75 years or older. This is an I statement. The USPSTF recommends against teaching breast self-examination (BSE). This is a D recommendation. The USPSTF concludes that the current evidence is insufficient to assess the additional benefits and harms of clinical breast examination (CBE) beyond screening mammography in women 40 years or older. This is an I statement. The USPSTF concludes that the current evidence is insufficient to assess the additional benefits and harms of either digital mammography or magnetic resonance imaging (MRI) instead of film mammography as screening modalities for breast cancer. This is an I statement.

Dr. Diana Petitti, a professor of biomedical informatics at Arizona State University and vice chair of the current task force, told The New York Times the panel knew the recommendations would surprise many women, but, she said, “We have to say what we see based on the science and the data.”

Frankly, I was surprised by the conclusion that self breast exams are not considered useful. News stories this week have included many anecdotes from women who found a lump that turned out to be cancerous, and every doctor I heard interviewed said that women should definitely contact their physician if they notice any changes in their breast. But what we’re learning is that feeling our own breasts for lumps is not statistically effective, and women who do self breast exams get twice as many biopsies.

The World Health Organization concurs: “There is no evidence on the effect of screening through breast self-examination (BSE). However, the practice of BSE has been seen to empower women, taking responsibility for their own health. Therefore, BSE is recommended for raising awareness among women at risk rather than as a screening method.”

Around 37 million mammograms are done each year. So what’s the problem there? For starters, mammograms use low-dose X-rays to examine the breast, and exposure to radiation can have a cumulative effect on the body. And they’re imperfect. About half of all premenopausal women, and one-third of postmenopausal women, have dense breasts, which makes their mammograms more difficult to read.

Mammograms produce false-positive results in about 10 percent of cases, leading to anxiety that can last for years, unnecessary and sometimes-disfiguring biopsies, and unneeded treatment, including surgery, radiation and chemotherapy — each of which present their own complications and health risks, including an increased risk of other cancers and heart disease.

According to the National Breast Cancer Coalition, U.S. estimates show a woman’s cumulative risk for a false-positive result after 10 mammograms is almost 50 percent. The risk for undergoing an unnecessary biopsy is almost 20 percent. Barbara Brenner, executive director of Breast Cancer Action, told me last year that research indicates that having more biopsies increases the risk of breast cancer, though the reason is unclear (read my post here).

Women are constantly being told “early detection saves lives,” but in reality we know some breast cancers, by the time they’re found, cannot be treated. Other cancers will never be life-threatening, and some will respond to currently available treatments. Unfortunately, the type of cancer cannot be determined at the time of diagnosis, which means we don’t know for sure whether the treatment will cause more harm than the cancer.

If you’re reading this and thinking you still want to keep that scheduled mammogram, you should certainly do so.

“No one is saying that women should not be screened in their 40s,” said Petitti, the task force vice chair. “We’re saying there needs to be a discussion between women and their doctors.”

Dr. Amy Abernethy of the Duke Comprehensive Cancer Center said she agrees with updated recommendations.

“Overall, I think it really took courage for them to do this,” she said. “It does ask us as doctors to change what we do and how we communicate with patients. That’s no small undertaking.”

Finally, I want to address the insurance question. At this point, insurance companies and Medicare administrators are saying that they will continue to pay for mammograms. Here’s what may change in the future, according to The New York Times:

The guidelines are not expected to have an immediate effect on insurance coverage but should make health plans less likely to aggressively prompt women in their 40s to have mammograms and older women to have the test annually. Congress requires Medicare to pay for annual mammograms. Medicare can change its rules to pay for less frequent tests if federal officials direct it to. Private insurers are required by law in every state except Utah to pay for mammograms for women in their 40s. But the new guidelines are expected to alter the grading system for health plans, which are used as a marketing tool. Grades are issued by the National Committee for Quality Assurance, a private nonprofit organization, and one measure is the percentage of patients getting mammograms every one to two years starting at age 40. That will change, said Margaret E. O’Kane, the group’s president, who said it would start grading plans on the number of women over 50 getting mammograms every two years.

For more information, here are some good stories and links:

NPR: All Things Considered looks at the research.

Washington Post: A good overview of the guidelines and cost controversy.

ScienceBlogs: “From my perspective, these new recommendations are a classic example of what happens when the shades of gray that make up the messy, difficult world of clinical research meet public health policy, where simple messages are needed in order to motivate public acceptance of a screening test,” writes Orac. “It’s also an example where reasonable researchers and physicians can look at exactly the same evidence for and against screening at different ages and come to different conclusions based on a balancing of the potential benefit versus the cost.”