A survey of cancer doctors finds that some believe they get paid more when they administer their patients’ chemotherapy and other drugs, raising concerns about conflict of interest and the potential for overtreatment.

Researchers found that oncologists, surgeons and other cancer specialists who get paid based on the number of services they provide were seven times more likely to say their pay increases when they oversee their patients’ chemotherapy treatments, compared to doctors who are paid a flat rate or salary.

“I think there is evidence out there that doctors are very responsive to financial incentives… So I think some patients should realize that doctors who are prescribing chemotherapy may be benefiting financially,” said Dr. Nancy Keating from Boston’s Harvard Medical School and Brigham and Women’s Hospital, the study’s senior author.

According to Keating and her colleagues, who published their study in the Journal of Clinical Oncology on Wednesday, some cancer doctors offer chemotherapy and other therapies in their offices.

Indeed, the researchers note, previous studies have found that as much as 65 percent of an oncologist office’s income typically comes from administering treatments. The rest comes from evaluating and managing patients’ cancers.

There are some advantages to patients in getting treatments at their doctors’ offices, such as not having to travel to a hospital, but some observers worry the practice gives doctors incentive to prescribe more chemotherapy or more expensive drugs because they’ll make more money.

In the last decade, the U.S. government tried to reduce the profit margin doctors were able to make by administering chemotherapy to their patients, but Keating told Reuters Health that didn’t solve the problem.

“I think there is some evidence out there that doctors just started prescribing more profitable drugs. So this is still an issue,” she said.

While the study could not determine whether patients received any unnecessary treatments, the researchers wanted to see whether doctors believe their pay is tied to their ability to give patients chemotherapy.

The researchers used a survey from 2005 through mid-2007 of 480 oncologists, who treated patients from across the country.

Overall, most participants said their income would be unaffected by prescribing chemotherapy or other drugs, or by referring patients to other specialists or hospices.

But 27 percent of the doctors said their pay would increase based on how much chemotherapy they administered and 25 percent said they’d get paid more if they administered more growth factors, such as so-called hormonal drugs, that regulate cell growth.

Doctors who were in some way paid based on how many services they provide - known as fee for service - were about seven times more likely to say their incomes would increase if they administered more chemotherapy or growth factors, compared to doctors who got a flat salary.

Doctors who had their own practices or were part of a smaller oncology group were about nine times more likely to say their income would increase if they administered their patients’ chemotherapy, compared to those who worked in a hospital.

“It really is pretty substantial differences. And often, I don’t think people pay that much attention to where their doctor works, but I think it does make a difference,” Keating said.

But Dr. Yu-Ning Wong of the Fox Chase Cancer Center in Philadelphia cautions that the new study only looks at whether the doctors believed their pay would increase if they could administer chemotherapy or other treatments.

“It didn’t say it actually did,” said Wong, who wrote a commentary accompanying the study.

She also told Reuters Health that she would not want cancer patients thinking they are receiving unnecessary care or treatments based on this study.

Still, Keating and her fellow researchers say, there needs to be a new way to pay doctors “to counter or eliminate these incentives to decrease unnecessary care and ensure that health care resources are used most effectively.”

Until then, Keating said patients should feel free to ask doctors whether they’ll benefit financially from their treatments.

“It’s certainly something I would want to know,” she said. “But I agree it’s not an easy thing to ask, but I do think it’s something to be aware of and I think it’s a fair question to ask.”

SOURCE: Journal of Clinical Oncology, online December 26, 2012.