CHICAGO (Reuters) - Cancer doctors should consider the financial as well as the medical impact of treatment for patients as healthcare costs continue to grow faster than the overall economy, according to experts in Chicago at the annual meeting of the world's largest organization of oncologists.

The American Society of Clinical Oncology is developing a system to rate drugs for advanced cancer based on a combination of benefit, side effects and price. The cost of such drugs can easily run into tens of thousands of dollars a year, even though many have been shown to extend the lives of later-stage cancer patients by just a few months.

"The problem is that the current system is unsustainable because it threatens access to high-quality cancer care," said Dr. Neal Meropol, chief of hematology and oncology at University Hospitals Case Medical Center in Cleveland.

The price issue has led some doctors to balk. In April 2013, more than 100 leukemia specialists complained in the American Society of Hematology's journal "Blood" that cancer drug prices were "too high, unsustainable, may compromise access of needy patients to highly effective therapy and are harmful to the sustainability of our national healthcare systems."

Insurers are looking to partner with doctors to reduce the chance of unnecessary spending.

"There are therapies that have high value and there are therapies that may not have much value," said Lee Newcomer, a senior vice president at UnitedHealth Group Inc.

He noted insurance companies' motives are viewed with suspicion when it comes to deciding whether a treatment is cost-effective, so having ASCO play a key role in establishing such guidelines would be crucial to their implementation.

Gregory Rossi of AstraZeneca stressed that any conversation about the value of cancer drugs needs to take into account the benefits of new, targeted cancer drugs that are based on an understanding of the biology of cancer.

"There are things we can do today that were unable to do a few years ago," Rossi said.

Rossi said drug companies should be rewarded for meaningful innovation.

But former Obama health adviser Dr. Ezekiel Emanuel had little sympathy for that argument.

"Everyone wants continued innovation," he said, while noting that the price of some cancer drugs, such as Novartis' Gleevec, have tripled since they first reached the market despite the launch of new competitors.

He noted that Gilead Sciences Inc has taken a lot of flack for its $84,000-per-treatment drug for hepatitis C infection, even though it cures the disease.

"Seems like a good value to me," he said. "One-time treatment over a few months and yet we are having a lot of consternation because of the cost."

Cancer doctors, he suggested, need to do much more to consider both the volume and the price of the treatments and tests they prescribe for patients.

"We are not doing everything we can to lower costs," he said.