Current recommendations from different health organizations, including the American Cancer Society and National Comprehensive Cancer Network, are mixed. Generally these recommendations advise the average woman to start mammograms somewhere between the ages of 40 and 50, and at intervals between every one to two years.
In the study published today, researchers from the Cancer Intervention and Surveillance Modeling Network attempted to understand which groups of women could benefit from more screening and which groups of women could benefit from less screening.
While their simulations found high-risk women with dense breast tissue would benefit from yearly screenings, women at average risk without dense breast tissue could benefit from less frequent screening. They suggested these women could get screened every three years, a departure from all current recommendations in the U.S., which generally recommend annual or biennal screening.
The researchers used simulation data, meaning that they did not conduct the study on living patients, but ran computerized models based on a large database from the Breast Cancer Surveillance Consortium.
Women can be at higher risk for breast cancer due to their genetics, environment or lifestyle according to the American Cancer Society. Almost 250,000 cases of invasive breast cancer will be diagnosed in 2016 for U.S. women, with over 40,000 deaths from breast cancer. The U.S. Preventive Services Task Force recommends screening every other year after 50, while the National Comprehensive Cancer Network and the American College of Radiology recommends annual screening starting at 40. The American Society of Breast Surgeons has a hybrid approach, encouraging conversations about risks and benefits with a doctor and encouraging some women to start earlier and others later.
In the new study, researchers found annual screening prevented approximately 15 to 20 breast cancer deaths per 1,000 high-risk women with dense breasts screened. In average-risk women without dense breast tissue, there was not a major change in cancer deaths averted if they switched from annual to triennial screening (4.7 deaths averted during annual screening compared with 3.4 deaths averted), but there was a large decrease in false positives. False positives can mean increased cost, anxiety and unnecessary procedures for patients.
The authors say these low-risk women could consider screening less frequently -- once every three years -- so there are fewer false positives leading to fewer unnecessary biopsies and lower costs.
Dr. Sheldon Feldman, a practicing breast surgeon and chief of breast surgery division of New York-Presbyterian Hospital/Columbia University Medical Center, as well as the president of the American Society of Breast Surgeons, said the study was interesting but the findings were too preliminary to lead to recommendations.
“Whether it should be every three years or two years, I would question," said Feldman.
“Certainly less frequent screening based on this data would be reasonable,” said Feldman; however as far as making specific recommendations, "it’s not ready for prime time."
He said the different recommendations have been confusing for both doctors and patients.
“There have been different recommendations from different groups, which change quite frequently,” said Feldman. “It is difficult to have consistent screening recommendations as the technology and landscape shifts with time.”
Despite technological gains in screening, Feldman said, it is “extremely difficult to study and to prove that the benefits outweigh potential risks" and to determine what the optimal screening interval should be.
"The goal, of course, is to find disease early without subjecting patients to unnecessary diagnosis and biopsies," he said.
The study authors said more research is needed to affect current guidelines, but that their findings suggest that it is important to look more closely at the association between breast density and the benefit as well as harm of screening.
Dr. Wendie Berg, a professor of radiology at the University of Pittsburgh School of Medicine and Magee-Womens Hospital of UPMC, and one of the co-authors of the BI-RADS system, the widely-used standard for breast imaging classification, said she was concerned that women with less-dense breasts but over all high risk could be misclassified and not be screened as much as they should be, if these preliminary findings affected recommendations.
Berg said that risk models work great for a population, but are less effective for a specific patient.
"At the population level, we can identify women at high risk, but at the individual level they [data models] are not that great," she said. "I think at the end of the day, a woman needs to advocate for herself to get the best screening possible to find breast cancer early."
Dr. Anish Ghodadra is a chief resident at the UPMC Department of Radiology in Pittsburgh and is currently working in the ABC News Medical Unit.
Dr. Jennifer Chevinsky is a transitional medical resident at Lehigh Valley Health Network in Allentown, PA and will be continuing on to Loma Linda University Medical Center for her Preventive Medicine Residency. She is a resident in the ABC News medical unit.