Mammograms Every Year or Every Other Year?

Breast cancer screening mammography every other year okay for women between 50 and 74

(RxWiki News) Quick – if you’re 55, how often should you have a mammogram? Every year or every two years? What if you have dense breasts? What if you’ve taken hormone therapy for menopause symptoms?

A new study suggests that women between the ages of 50 and 74 should have screening mammograms every other year.

That recommendation remains regardless of breast density (how fibrous the breast tissue is) or hormone therapy use.

However, one breast cancer screening specialist disagrees with this assessment.

"Talk to your doctor about a breast cancer screening program that’s right for you."

In 2009, the US Preventive Services Task Force recommended that women aged 50 to 74 receive screening mammograms every two years (biennial) instead of every year.

This recommendation did not account for other breast cancer risk factors, including breast density and hormone therapy use.

Hormone therapy has been established as a risk factor for breast cancer – a finding that’s now being questioned.

The new study, led by Karla Kerlikowske, MD, of the University of California, San Francisco, evaluated the benefits (early cancer detection) and harms (false positive results and referrals for biopsies) relating to the frequency of screening mammograms according to age, breast density and postmenopausal hormone therapy use.

False positive results are screenings that show the presence of cancer which further testing shows to be false.

Researchers analyzed data from 11,474 women with breast cancer and 922,624 without breast cancer. The information, which spanned 1994 to 2008, was gathered from mammography facilities that participate in the Breast Cancer Surveillance Consortium (BCSC).

“Our results are consistent with those of randomized controlled trials, a population-based screening program, a community-based study, and statistical models that report annual mammography has minimal if any additional benefit over biennial mammography for women aged 50 to 74 years,” the authors wrote.

Women in this age group who had biennial screenings were not more likely to have advanced disease or larger size tumors.

Women 40 to 49 years old with extremely dense breasts may want to consider annual mammography because biennial screenings are more likely to detect advanced disease, according to the researchers.

False positive results and referral to biopsies (harms) occurred in 65.5 percent of women ages 40 to 49 years with extremely dense breasts, and in 65.8 percent of postmenopausal women who used hormone therapy. False positives were less frequent (12.1 to 30.7 percent) in women ages 50 to 74 with less dense breasts who had mammograms every two or three years

The authors said "[...] women aged 50 to 74 years, regardless of breast density or hormone therapy use, can undergo biennial rather than annual mammography because biennial screening does not increase the risk of presenting with advanced disease but does substantially reduce the cumulative risk of a false positive mammography result and biopsy recommendation."

"Women aged 40 to 49 years with extremely dense breasts who choose to undergo mammography should consider annual screening to decrease the risk of advanced stage disease but should be informed that annual screening leads to a high cumulative probability of a false positive mammography result because of the additional screening examinations," the authors concluded.

“The study is fundamentally flawed. They compared apples to oranges. The groups were looked at retrospectively and are completely different women,” Daniel B. Kopans, MD, professor of radiology at Harvard Medical School and senior radiologist in the Breast Imaging Division of Massachusetts General Hospital, told dailyRx. "Why were some screened every year vs. every two years?  They have no idea.  This was not a randomized trial which is the only way to look at the effect of screening interval."

Dr. Kopans continued, "They do not actually tell us the total number of women screened each year vs. every two (or three) years so that their math cannot be checked."

"It is fairly meaningless. Do cancers actually stop growing so that you can wait two or even three years and they will have not changed in size?  They do not even try to explain it because they know it makes no biological sense," Dr. Kopans said.

This study was published March 18 in JAMA Internal Medicine. The research was supported by grants from the National Cancer Institute. No conflicts of interest were reported.

Review Date: 
March 18, 2013