Congressional watchdogs wonder why Department of Health and Human Services officials aren't doing something about Medicare providers who line their pockets by ignoring less-expensive cancer treatments in favor of costlier approaches in which they have a financial interest.

The Government Accountability Office reports that the use of intensity-modulated radiation therapy, one of the most expensive cancer treatments available, more than tripled between 2006 and 2010 among Medicare providers who refer patients to their own practices or to a group in which they have a financial stake.

Use of the more expensive IMRT therapy decreased during the same period among providers who refer patients to other providers.

Self-referral for IMRT rose from 80,000 referrals in 2006 to 366,000 in 2010, according to a GAO report released Thursday. The rise in referrals couldn't be traced to age, location or health reasons, according to the report.

"These analyses suggest that financial incentives for self-referring providers -- specifically those in limited specialty groups -- were likely a major factor driving the increase in the percentage of prostate cancer patients referred for IMRT," GAO said.

GAO is asking Congress to rein in the spending by requiring providers to disclose any financial interest they may have in a recommended treatment, something HHS doesn't have the authority to do on its own. The congressional watchdog agency also wants HHS to flag and monitor self-referrers.

But HHS disagrees, saying monitoring self-referrers would be complex and wouldn't keep them from over-prescribing IMRT.

"On the basis of HHS's written response to our report, we are concerned that HHS does not appear to recognize the effects IMRT self-referral can have on beneficiaries and the Medicare program," GAO responded.

Besides the integrity concerns of doctors choosing treatments for financial reasons, the GAO noted the practice poses a serious health risk for patients whose treatments are based on money instead of health concerns.

Choosing the more expensive treatment also makes taxpayers pay more, driving up Medicare costs.

The rise in costly self-referral has been under scrutiny for several years -- a 2010 Wall Street Journal story highlighted the prevalence of the practice, and the GAO's investigation was prompted by a request from members of Congress.

Self-referral is generally prohibited by federal law, but IMRT is one of the exceptions, according to the GAO.

Because reimbursements for the services varies widely, GAO didn't give an estimate of how much self-referral has cost taxpayers or benefitted providers.

HHS did not respond to a request for comment.