With conflicting recommendations about the right age for women at average risk to begin breast cancer screenings and how often to be tested, it’s no wonder that some women are confused. While two of the major health organizations recommend mammograms starting at age 40, the American Cancer Society in 2015 started recommending that screening begin at age 45 and, starting at age 55, that women only have a mammogram alternating years. These guidelines were put in place to reduce the so–called harms of screening, but for Debra L. Monticciolo, MD, professor of radiology at the Texas A&M College of Medicine and Section of Breast Imaging chief at Baylor Scott & White Health Central Texas, such guidelines are misguided, as they could cause cancer to be caught at later stages and will not reduce the rate of overdiagnosis.

Monticciolo and her colleagues recently published an article in the Journal of the American College of Radiology reporting the results of a study in which they found no cases of a cancerous tumor found via mammography shrinking or spontaneously disappearing.

“People who question the need to screen for breast cancer often tell patients, ‘The cancer may just go away on its own,’” Monticciolo said. “Those of us who actually work in breast cancer know that’s ridiculous, but we’ve not had a scientific way to approach the problem.”

To address this, Monticciolo and her colleagues gathered data from 42 fellows of the Society of Breast Imaging – all of whom are experts in the field – about how untreated, but biopsy–proven, breast cancers progressed. They gathered a total of about 6.9 million mammogram results over a ten–year period, of which 240 were cases of untreated invasive breast cancers and 239 were untreated cases of ductal carcinoma in situ (DCIS). “None of the cancers regressed,” Monticciolo said. In other words, not one of either type of disease disappeared or even became smaller at follow up exams, according to the fellows surveyed.

Therefore, guidelines of less–frequent mammograms simply delay the diagnosis of breast cancer. “Lengthening the screening interval or waiting until a woman is 45 or 50 to screen will not prevent whatever small amount of overdiagnosis that may exist; it will simply delay it,” Monticciolo said. “Most of the improved survival rates of breast cancer are because of early detection.”

On the other hand, the risks of mammography are small. The doses of radiation are relatively low – about the same amount someone gets naturally every seven weeks. Over 90 percent of people get a normal result from a mammogram, and even for those called back for additional imaging, most don’t end up needing a biopsy. “When you weigh the stress and worry for those who have a possible abnormal result against the mortality rates of breast cancer, most women would choose to be tested,” Monticciolo said. “Screening can reduce the mortality from breast cancer by 40 percent.” Mammograms are also relatively cost effective and can generally be done in just a few minutes.