PET Scan Can Detect Chemo Success Faster, Improve Cancer Therapy

by Tina Kells | March 5, 2009 at 11:24 am

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An old technology, the PET scan, is breathing new life into tracking the success of cancer treatments. Cancer patients undergoing chemo are injected with a radioactive substance prior to being given a PET scan that allows doctors to detect how well a chemotherapy course is performing.

Doctors typically must wait weeks or months to see if a treatment is shrinking tumors or at least halting their growth. But researchers are exploring a new use for medical imaging that could shorten the stay in purgatory, possibly revealing within a few days whether chemo is working.

That speed could save both lives and money. It would allow doctors to switch more quickly from an ineffective drug to a different one, and save health care dollars by waving doctors off expensive but futile treatments.

The same approach may also prove useful for monitoring radiation therapy.

This experimental imaging relies on a familiar hospital workhorse: PET scans, typically used for things like detecting cancer or revealing the effects of a heart attack. Unlike CT scans or MRIs, PET scans can show a tumor's internal activity, not just its size.

When used to assess the effects of cancer treatment, it can reveal inside information about what the therapy is doing to a tumor even when there's no outward sign.

Tracking cancer treatment with the PET scan shows doctors how well the chemotherapy is working more quickly than current tests do and with greater accuracy. Current methods can take weeks or months to guage chemotherapy success. The modified PET scan can shorten that time frame to a matter of days.

There are other advances in PET scan technology on the horizon that could offer even faster results to cancer patients undergoing chemotherapy and/or radiation treatments. Faster measures of cancer therapy success will save lives and improve the way that cancer patients live while undergoing treatment.

Farther out on the research horizon is a PET scan that uses injections of a different radioactive material and has revealed chemotherapy's impact even faster. Larson figures it will be especially useful for assessing newer drugs that aim to stop a patient's cancer from growing rather than killing the tumor.

This scan is called FLT PET, after radioactive fluorothymidine. These scans show whether cancer cells are dividing. Uncontrolled division is a hallmark of active cancer, and stopping that division should be an early effect of successful chemotherapy.

"Our hope ... is you might be able to give a single dose of a chemotherapy agent and within a day or two figure out whether the tumor is going to respond," says Dr. Michael Graham of the University of Iowa.

If the tumor doesn't respond, doctors would "go on to Plan B," he said. "This is really ... giving us the ability to tailor the therapy to the disease."