Primary-care physicians and gynecologists continue recommending breast cancer screening for younger and older women despite changes to breast cancer screening guidelines, a study published Monday found.

Trust in different guidelines and a physician's specialization affect their screening recommendations, according to the study published in the Journal of the American Medical Association Internal Medicine.

The optimal time to begin and end breast cancer screening and how often to have screenings are highly debated topics among professional organizations. The American Congress of Obstetricians and Gynecologists is a relatively pro-screening organization. It recommends yearly mammograms for women 40 and older. The American Cancer Society revised its guidelines in 2015 to encourage personalized screening decisions for women ages 40 to 44, with routine mammograms starting at 45. The U.S. Preventive Services Task Force revised its guidelines in 2016 to encourage more personalized screening decisions rather than routine mammograms for women ages 40 to 49.

The researchers conducted this study as part of a broader project to understand what factors affect whether physicians adhere to the recommendations given by different organizations. A physician recommendation is one of the most important determinants of whether people obtain screening.

“Sometimes when cancer screening guidelines change, they recommend that we do less, that we start screening later, screen less frequently and end screening after a certain age,” said Craig Pollack, a co-author of the study and an associate professor of medicine at Johns Hopkins University. “I think this can be incredibly challenging for doctors and patients because we are used to doing things in a certain way, so telling people to do less can run counter to our prior experiences caring for patients,” he said.

Of all physicians surveyed, 26 percent reported primarily trusting the American Congress of Obstetricians and Gynecologists guidelines, 23.8 percent in the American Cancer Society guidelines and 22.9 percent in U.S. Preventive Services Task Force guidelines. Recommendations differed sharply based on which guidelines physicians trust, the survey found.

Physicians who trusted the ACS and ACOG were significantly more likely than their counterparts who trusted the U.S. Preventive Services Task Force to recommend breast cancer screening to women younger than 45, the study found.

“With different guidelines for mammography, recommendations for screening can be confusing not only to patients, but also to ordering physicians,” said Mitva Patel, a breast radiologist at the Ohio State University Comprehensive Cancer Center-Arthur G. James Cancer Hospital and Richard J. Solove Research Institute, who was not involved in the new survey.

The researchers mailed 2,000 surveys to physicians who were randomly selected based on whether they reported providing primary care or general gynecologic care to women 40 or older.

Among all respondents, 81 percent of physicians recommended screening to women ages 40 to 44, and 88 percent recommended screening for women ages 45 to 49. As far as when to discontinue mammograms, only 67 percent of the surveyed physicians recommended screening to women 75 or older, the study found.

Different guidelines from professional societies reach different opinions in part because they weigh the available evidence by comparing the benefits of screening, which can help find cancer earlier and potentially help women live longer, against the potential downsides of screening, which include false positives in mammograms and over-diagnoses. Personalized decision-making exists to help women understand those benefits and risks while also allowing them to incorporate their own values in these decisions.

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