In recent years there has been much discussion and conflicting opinions about when and how often women should be screened for breast cancer. Specifically, the 2009 U.S. Preventive Services Task Force touched off a wave of controversy when it recommended screening mammograms every two years starting at age 50. The previous standard for women was a baseline mammogram at age 40 and then regular screening every year or every two years following.
The task force rationale was that mammograms for average-risk women in their 40s posed considerable harms, such as false-positive results causing anxiety or leading to unnecessary invasive procedures.
Instead, they suggested that women in their 40s who were at average risk of breast cancer should discuss the pros and cons with their doctors and then decide about the value of screening. Meanwhile other organizations, including the American Cancer Society, continued to advise women 40 and older to get yearly screening mammograms.
This left 40-something women and their doctors without concrete answers, such as: What risk factors make early screening worth the risk of unnecessary procedures and associated cost?
Two new studies set out to help quantify the risk/benefit ratio of mammograms for women with various risk factors. They found that women who have a family history of breast cancer or unusually dense breast tissue, should have their first test at age 40 and repeat the exam at least once every other year.
The first study analyzed data from 66 published studies to identify specific factors that increased breast cancer risk for women ages 40-49. Of 13 possible risk factors, they found extremely dense breast tissue or a direct relative with breast cancer (parent, sibling or child) doubled the risk of breast cancer in women 40 to 49. Breast density is determined by mammography.
About 13 percent of women in their 40s have extremely dense breast tissue and 9 percent have a first-degree relative with breast cancer.
Then they used computer modeling to predict the outcomes of 44,000 simulated women based on two scenarios: having their first mammogram at age 50 or at age 40. They then compared the rates of false alarms, breast cancer diagnoses and mortality in both groups.
The computer models indicated that higher-risk women 40 to 49 who start every-other-year screenings at age 40 have the same benefit-harm ratio as average-risk women 50 to 74 who have mammograms every two years.
In the course of their study, the researchers also found small differences in benefits between film mammography and the newer digital mammography. The digital forms had more false-positives.