mardi 20 octobre 2015

What You Should Know About The New Breast Cancer Screening Guidelines

What You Should Know About The New Breast Cancer Screening Guidelines

The American Cancer Society has issued newly revised guidelines on mammography and breast cancer screening. Here a woman is screened in Los Angeles in 2010. (Damian Dovarganes/AP/File)

The American Cancer Society has issued newly revised guidelines on mammography and breast cancer screening. Here a woman is screened in Los Angeles in 2010. (Damian Dovarganes/AP/File)

If you follow women’s health, there’s big news today from the American Cancer Society, which just issued newly revised (and frankly head-spinning) guidelines on mammography and breast cancer screening. Why all the fuss? Because breast cancer is the most common cancer among women worldwide; in the U.S., about 230,000 cases are expected to be diagnosed in 2015 with an estimated 40,300 deaths. And when such an influential organization changes its recommendations, it can radically shift the conversations between doctors and patients.

Here’s the crux of the news: In 2003, the ACS recommended annual mammography screening for all women starting at age 40 and continuing as long as women remain healthy. The group also recommended clinical breast exams (CBE), which is simply when your doctor examines your breasts, periodically for women in their 20s and 30s and every year for women 40 and up.

The new recommendations, published Tuesday in The Journal of the American Medical Association, change all of that, and come at a time of growing awareness about the potential downside of screening and the harms of over-diagnosis.

Here are the new guidelines from the report (my bold added):

The ACS recommends that women with an average risk of breast cancer [no family history, genetic predisposition, etc.] should undergo regular screening mammography starting at age 45 years (strong recommendation).

Women aged 45 to 54 years should be screened annually (qualified recommendation).

Women 55 years and older should transition to biennial screening or have the opportunity to continue screening annually (qualified recommendation).

Women should have the opportunity to begin annual screening between the ages of 40 and 44 years (qualified recommendation).

Women should continue screening mammography as long as their overall health is good and they have a life expectancy of 10 years or longer (qualified recommendation).

The ACS does not recommend clinical breast examination for breast cancer screening among average-risk women at any age (qualified recommendation).

Nancy Keating, professor of health care policy at Harvard Medical School and a primary care doctor at Brigham and Women’s Hospital in Boston, co-wrote an editorial accompanying the new guidelines.

In an interview, Keating described the four most striking aspects of new recommendations:

1) the more conservative starting age for mammography (45 vs. 40 years), which brings the ACS recommendations closer to the guidelines from another important advisory group, the U.S. Preventive Services Task Force (USPSTF), which endorse biennial screening for women aged 50 to 74 years;

2) the proposal for more frequent (annual) screening intervals among women aged 45 to 54 years;

3) the recommendation against routine screening CBE, a marked deviation from prior ACS guidelines and a stronger statement than that of the USPSTF, which in 2009 concluded that the evidence was insufficient to recommend for or against CBE;

4) the recommendation to stop screening among women with a life expectancy of less than 10 years.

Keating said that for some women, the new guidelines should make things easier because both the cancer society and the federal preventative task force basically line up on guidance. The big disagreement, Keating said, is over what to do for women age 45-54.

“This exemplifies the uncertainties of evidence,” Keating said. “Two really smart groups of people looked at the evidence and came up with different conclusions.”

Specifically, the cancer society included in its analysis findings from a large, observational study of mammography. That study concluded that for premenopausal (but not postmenopausal) women, annual mammograms were associated with smaller tumors.

“Smaller tumors should be better,” Keating said, “but we don’t have long-term data from that population. So we don’t know for sure if this leads to better outcomes.”

The context of all this is a greater awareness of the harms of false positive mammograms and the the real harm of over-diagnosis, which basically is when you’re diagnosed with a cancer that would never become “clinically evident” in your lifetime except for the fact that you underwent screening. This over-diagnosis, of course, can lead to the real harm of treatment for a cancer that you may never have needed to deal with.

All of this is complicated and nuanced. That’s why it’s more important than ever for patients to have in-depth conversations with their doctors about what kind of screening is or isn’t right for them, Keating said, and what level of risk they can tolerate. These are intimate discussions, obviously, because every woman is completely different in this context.

Keating offered a few numbers that sometimes help women ages 40 to 50:

“If …10,000 women have a mammogram annually for 10 years, about five to 10 of them will have their lives saved; 30 to 60 will die of breast cancer anyway, regardless of the mammogram; 200 to 300 will have breast cancer that can be cured; 6,000 will have at least one false positive test; about 700 to 800 will have one unnecessary biopsy; and among the 200 to 300 women diagnosed with breast cancer, 30 to 60 will have an over-diganosed cancer, meaning their cancer never would have been clinically evident, yet they’ll be treated like the others.”

Click to enlarge. (Source: The Journal of the American Medical Association)

Click to enlarge. (Source: The Journal of the American Medical Association)

As for the recommendation to stop the breast exams, Keating says:

I follow the reasoning of the guideline panel… there is no good evidence of benefit (because no studies have rigorously compared clinical breast exam with no clinical breast exam), and some evidence of harm (false positives primarily) and importantly, to do it right, it takes 6 minutes … which is a lot of time and a big opportunity cost that docs could better spend on a shared decision about mammography. That said, it is important to note that this is based on “very low” quality of evidence.  I’ve still been doing them, but I’ve been starting to talk with my patients about the limited evidence and these new recommendations against doing them routinely, and letting them know that we should continue to discuss if we think it makes sense to continue them.

Still confused? Here’s the conclusion of Keating’s editorial:

…it is important to remember and emphasize with average-risk women older than 40 years that there is no single right answer to the question “Should I have a mammogram?”

Instead, women should be supported in estimating and understanding their risk of developing breast cancer and articulating their values and preferences so that clinicians can help them make informed decisions.

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