Stacey Burling / The Philadelphia Inquirer

PHILADELPHIA — Patients enduring the excruciating pain of cancer that has spread to the bones are often given multiple doses of radiation.

There is strong evidence, however, that one dose controls pain as effectively as 10 or more. In addition, one treatment is cheaper and far more convenient for patients who already have plenty on their minds.

Yet a new study by University of Pennsylvania researchers has found that only 3.3 percent of Medicare patients receiving radiation for prostate cancer that had metastasized to the bone received a “single-fraction” treatment.

While 10 fractions, or treatments, was long considered the standard, more than half the 3,050 patients whose records were reviewed received more than 10 fractions.

About 250,000 patients a year suffer from cancer bone pain, said Justin Bekelman, a radiation oncologist at Penn Medicine’s Abramson Cancer Center, who led the study. Typically, their cancers cannot be cured. Radiation only reduces the pain. It does not extend life.

Bekelman said the study illustrates how difficult it is to change medical practice, especially when payment systems reward doctors for sticking to the status quo.

Doctors are paid more when they give more treatments. According to the study, published last week in the Journal of the American Medical Association, Medicare pays an average of $1,873 for a single treatment compared with $4,967 for a group of treatments.

“It’s profoundly difficult to change practice,” Bekelman said. While he said most doctors are simply doing what they have always done, he conceded that it might take more than publicity about newer evidence to change their behavior.

“Pretty clearly, practice change might only materialize if payment reform incentivizes high-quality care,” he said. “In this case, it’s not incentivizing high-quality care. In fact, it’s the opposite.”

Ezekiel Emanuel, chair of Penn’s department of medical ethics and health policy, and senior author of the study, called that “a perfect example of misalignment” between goals and financial incentives. Insurers should begin paying doctors the same amount for one radiation treatment as for a series, he said.

Single-fraction patients are given a relatively larger dose in one treatment. In multiple-fraction radiation, patients get smaller doses, usually on consecutive work days. That means patients, often older and not feeling well, must come repeatedly to the treatment center.

Bekelman said a large clinical trial in 2005 concluded that the two regimens provide equal pain control with similar side effects. Some say patients are more likely to require a second round of treatment with single-fraction therapy, but Bekelman said evidence was mounting that the two forms of treatment are equal, even when it comes to retreatment.

The American Society for Radiation Oncology 2011 guidelines favored a single treatment, he said. ASTRO and the American Academy of Hospice and Palliative Medicine include multiple-fraction radiation in lists of potentially unnecessary treatments doctors and patients should discuss.