Is My Chemo Working? Scans May Give Faster Answer
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 tumors 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 theres no outward sign.
To do a PET scan, doctors inject a patient with a radioactive substance that shows up on the scan in places where certain processes are happening – like hungry cancer cells gobbling up a lot of blood sugar. Think of it as looking around your neighborhood late at night for light in bedroom windows to see who is still awake.
Many cancer patients get PET scans now to assess their disease before treatment, or to spot recurrences later on. But except for lymphoma, PET scans arent routinely used to get a quicker answer on how cancers are responding to therapy.
The new research tests both standard PET scans and a newer approach that involves injecting a different tracer substance.
The standard scan, which looks for blood sugar usage, has gotten good results in tests with a variety of tumors including breast, prostate, colorectal and esophageal cancers, said Dr. Steven Larson of the Memorial Sloan-Kettering Cancer Center in New York.
“I think its going to be extremely valuable for most tumors where there are effective treatments,” he said. Some experiments have revealed chemos effects within 10 days to two weeks.
As a practical matter, the goal of researchers is to convince federal regulators to cover the procedure under Medicare and Medicaid, which would open the door to routine use. That might take two or three years, he said.
Farther out on the research horizon is a PET scan that uses injections of a different radioactive material and has revealed chemotherapys impact even faster. Larson figures it will be especially useful for assessing newer drugs that aim to stop a patients cancer from growing rather than killing the tumor.
“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 doesnt respond, doctors would “go on to Plan B,” he said. “This is really … giving us the ability to tailor the therapy to the disease.”
Research into FLT PET is still in the early stages. Graham said there are maybe a dozen published human studies so far, most involving too few patients to draw a firm conclusion.
One report that impressed him involved 28 patients in Korea who were treated for advanced lung cancer – just like Stevens, who had to wait six weeks to learn whether it was working. The researchers reported that just one week after treatment began, they could tell with 93 percent certainty which patients would eventually respond to the drug and which would not.
In a much smaller study at the University of Wisconsin in Madison, seven patients with acute myeloid leukemia were scanned at various times during a week of aggressive chemotherapy. Normally, doctors wait a month after chemo is stopped to see if it worked. But the FLT PET scans offered an answer as soon as a day after treatment started.