Early Breast Cancer Screening, Unnecessary and Risky
A new study out of Norway shows that women who screen early for breast cancer are likely to get the wrong result--a false positive--called overdiagnosis. This industry term, “overdiagnosis” describes the identification and treatment of symptoms of cancer, where none exist.
“Any screening test that attempts to identify a disease early on will come with a risk of overdiagnosis,” says Mette Kalager, study researcher at Telemark Hospital, Norway.
In the study, Kalager and colleagues analyzed cases of invasive breast cancer over a 10 year period beginning in 1999, the inception year for mammogram screening for women in Norway, from ages 50 to 69. “Different regions of the country began the screening program at different times, and the researcher compared cases among women offered screening from those not offered screening.”
During the 10 year study some 7,800 women were diagnosed with breast cancer of which 15 to 25 percent were overdiagnosed. This means between 1,169 and 1,950 women thought they were pre-cancer patients and were taking the necessary precautions and treatments that went along with that diagnosis.
Overdiagnosis is a real problem linked to early screening.Two important reasons to worry are: 1) it leads to further tests and possible, aggressive treatments in women, that are not needed, and are harmful, and 2) no current tracking tools are available to pinpoint which of the women fall in this category, to help reduce incidences of false positive treatments.
Most guidelines recommend mammograms for older women, but there are differences about what age they should start and how frequently they should be done. For example, women with a history of breast cancer in their family, and in particular their immediate family (parents and siblings) may require earlier testing than age 40, which is the starting age recommended by the American Cancer Society.
Compare the American Cancer Society’s age guideline to that of The U.S. Preventive Services Task Force (USPSTF), which recommends ages 50 to 74 years receive mammograms, every two years. Therefore the USPSTF is “against routine screening mammography in women aged 40 to 49 years.”
Kalager says, “You have to weigh the benefits and the harms, and you have to make up your mind [about] what is most important to you.”
Breast screening recommendations start at an earlier age in the United States than in Norway and for this reason overdiagnosis may occur more often for American women and should be a serious concern for them.
The study appears in the April 3 issue of the Annals of Internal Medicine; it also provides more clinical guidelines on breast cancer screening.