Blog | Wednesday, November 23, 2011

QD: News Every Day--Canadian task force recommends fewer mammographies


The Canadian Task Force on Preventive Health Care suggested fewer mammographies in a set of recommendations that mirrored those of the U.S. and U.K.

Key recommendations include:
--no routine mammography for women in their 40s because the risk of cancer is low in this group while the risk of false-positive results and overdiagnosis and overtreatment is higher
--routine screening with mammography every two to three years for women ages 50 to 74
--no MRIs to screen average-risk women, and
--no routine clinical breast exams or breast self-exam.

The full set of recommendations appear in CMAJ, the Canadian Medical Association's journal. One-page information pieces are available for both physicians and patients on the task force's website.

In the study, the Canadian task force noted the number needed to screen to prevent one death from breast cancer for women ages 40 to 49 years is 2,108. But the risk of a false-positive result from mammography is higher for women in their 40s. Screening 2,100 women in this age group once every two to three years for about 11 years would prevent a single death from breast cancer, but it would also result in about 690 women having a false-positive result on a mammogram, leading to unnecessary follow-up testing, and 75 women having an unnecessary breast biopsy.

The number needed to screen to prevent one death from breast cancer for women ages 50 to 69 years is 721. Screening 720 women in this age group once every 2–3 years for about 11 years would prevent a single death from breast cancer, but it would also result in about 204 women having a false-positive result on a mammogram and 26 women having an unnecessary breast biopsy.

Screening about 450 women ages 70 to 74 years once every 2–3 years for about 11 years would prevent one death from breast cancer, but it would also result in about 96 women having a false-positive result on a mammogram and 11 women having an unnecessary breast biopsy. No recommendation was made for women older than 74 because of a lack of data.

"There was no evidence that screening with mammography reduces the risk of all-cause mortality," state the authors. "Although screening might permit surgery for breast cancer at an earlier stage than diagnosis of clinically evident cancer (thus permitting the use of less invasive procedures for some women), available trial data suggest that the overall risk of mastectomy is significantly increased among recipients of screening compared with women who have not undergone screening."

An editorialist commented, "[T]hese guidelines are more balanced and more in accordance with the evidence than any previous recommendations."

The editorial continued that diagnosis of cancers that would otherwise be undetected leads to life-shortening treatments and mastectomies.

"The main effect of screening is to produce patients with breast cancer from among healthy women who would have remained free of breast disease for the rest of their lives had they not undergone screening," it continued.

"The best method we have to reduce the risk of breast cancer is to stop the screening program," it concluded. "This could reduce the risk by one-third in the screened age group, as the level of overdiagnosis in countries with organized screening programs is about 50%."

J. Leonard Lichtenfeld, MD, MACP, the Deputy Chief Medical Officer for the American Cancer Society, wrote that no screening takes it too far.

He wrote, "I say that such a position may not take us back to the 1960's, but not far from that. We will have more women having more mastectomies because the cancers are larger. And more women will have chest wall invasion, and more women will have lymph node involvement and our use of radiation and post-operative adjuvant chemotherapy will not get us back to baseline. Not to mention that the decline in breast cancer death rates in the United States that we have seen year over year since the early 1990's would likely stop at some point over the next 10 years."