The American Cancer Society (ACS) released new guidelines recommending that women undergo mammograms at 45 years old, revising its 2003 recommendation that breast cancer screenings should start at age 40, according to a news release from the organization.

After reviewing relevant literature on the benefits and harms of breast cancer screenings and questioning how often the screenings should be done, the ACS decided women do not need to have mammograms until they turn 45.

Additionally, women should have mammograms every two years until they turn 55 instead of every year, the group said. The ACS gave two reasons for this: 1. Breast cancer grows more slowly after menopause, and most women reach the postmenopausal stage at age 55; 2. The risk of getting more false positive results increases with more frequent screenings over time.

"The biggest evolution has been not in the American Cancer Society, but in the science of cancer screening and the evolution of health care in general," Richard Wender, ACS chief cancer control officer, told USA Today.

According to Wender, the new cancer screening guidelines adapt to the risk a woman faces as her age progresses. For example, a woman faces the highest risk of breast cancer at 45 years old, but getting a mammogram at a younger age gives a greater chance of getting false positive results, which could lead to unnecessary follow-up procedures.

The ACS also wants to avoid overdiagnosis of tumors that are not really harmful. These tumors may be detected by the screening test, but because doctors cannot tell if a tumor is harmful or not, they generally subject the patient to treatment, which can give them more harm than good. According to ACS, 1 to 10 percent of breast cancer cases are overdiagnosed, reported USA Today.

"Today, screening guidelines are expected to judge the balance between benefits and harms," he told NPR. "And that was actually not a standard approach in 2003, which was a time when virtually all of the emphasis was only on the potential benefits of screening."

The full text of the American Cancer Society's recommendations for breast cancer screening was published in the online Oct. 20 issue of JAMA.