(Reuters Health) - The kind of imaging U.S. women receive after treatment for non-metastatic breast cancer can vary widely, a new study finds.

While some women don't even get the recommended annual mammograms, others with similar low-risk cancers are receiving expensive PET and full body scans, which expose patients to higher levels of radiation, researchers reported in the Journal of the National Comprehensive Cancer Network.

Ultimately, "where you live has an effect on the amount of imaging you get," said the study's lead author, Dr. Benjamin Franc, of the University of California, San Francisco. "There was a 10-fold difference between the highest and lowest rates of high-cost scans."

Overall, nearly a third of the women in the study got those high priced scans.

These days, with high insurance deductibles, patients can end up paying a lot out of pocket. The cost for full body scans range from $2,000 to $8,000 - and that's for scans that aren't recommended in any of the guidelines for follow-up care in women with low-risk breast cancers.

"By spending money they don't need to spend now, patients could be risking their future because of an inability to pay later for medical care they really need," Franc said.

Beyond the issue of cost, there are concerns about radiation. Some of these scans expose patients to 20 times as much as radiation as they would encounter with a mammogram, Franc said, adding that there have been estimates that 0.4 percent of all cancers can be traced to radiation from imaging.

Franc said there were no real patterns in the data that would explain the variations in care. He and his colleagues suspect they have more to do with local physician preferences and practices than anything else.

The researchers scrutinized data from 36,045 women, ages 18 to 64, who had surgery between 2010 and 2012 for cancer in a single breast. To focus the study only on women with low risk cancers, the researchers included only patients who received no chemotherapy. The data for the study came from the Truven Health MarketScan Commercial Database, which breaks down information by metropolitan areas.

Current guidelines recommend that women with non-metastatic breast cancers get annual physical exams and mammograms only, and no full body or bone scans. One of the top factors predicting whether a patient would get one of these non-recommended scans was the metropolitan area she came from.

"It tells me that the existence of guidelines and the distribution of guidelines is not enough," Franc said.

Franc recommends that patients being offered one of these expensive scans ask their doctor why it's necessary.

The data used by Franc and his colleagues can't show whether the excess use of these high-cost scans is being driven by patients or physicians, said Dr. Nancy Keating, a professor of health care policy and medicine at Harvard Medical School and a primary care physician at Brigham and Women's Hospital.

"But I'd put money on it being the physicians and not the patients," Keating said. "While patients often ask for things, when it's really not indicated by the guidelines, the physician can explain that."

It's not clear what can be done to rein in this kind of over treatment. There was a time when policy experts thought that HMOs and insurance companies would bring costs under control.

"It would be interesting to know over time if restrictions in approvals and requirements for pre-certifications by insurance companies have impacted the ordering of these expensive imaging tests," said Dr. Dawn Hershman, a professor of medicine and epidemiology and leader of the breast cancer program at the Herbert Irving Comprehensive Cancer Center at Columbia University.

SOURCE: bit.ly/2NXXSHp Journal of the National Comprehensive Cancer Network, July 2018.