Precisely targeted radiation therapy can eradicate tumors that have spread to other parts of the body, offering more months or years of life to patients who have no other options, U.S. researchers reported on Wednesday.
They said new radiation techniques can attack metastases — tumors that have spread — one by one.
Experiments in 29 patients showed the radiation stopped all the tumors in six, or 21 percent, of the patients, for anywhere between 10 months and more than two years.
"This was proof of principle in patients who had failed the standard therapies and had few, if any, remaining options," said Dr. Ralph Weichselbaum of the University of Chicago Medical Center, who led the study.
Treatment doesn't always work
But the results were inconsistent — in another six patients, only the treated tumors grew, while in yet another six, untreated tumors remained and grew, the team at the University of Chicago Medical Center reported in the journal Clinical Cancer Research.
In eight of the patients, new tumors appeared but the treated tumors were stopped.
Higher doses of radiation have been shown to be safe for many places on the body and might work better, Weichselbaum said in a telephone interview.
He said more patients with a variety of cancers, including lung, head and neck, breast, colon and ovarian, are being treated now with higher doses and are surviving longer.
All have stage IV cancer, meaning it has spread to more than one place throughout the body. Almost all patients with stage IV cancer die, even with chemotherapy, except for patients with testicular cancer and some blood cancers.
"These patients had been through experimental treatments, so it is not like we got anybody who had standard of care left, Weichselbaum said.
Each volunteer got three doses of precisely targeted radiation to their tumors. New guided radiation techniques can limit the amount of damage to healthy tissue and new imaging techniques, such as CT and PET scans, can help doctors find tumors they previously might have missed.
Few serious side effects
All the patients had some fatigue but few had serious side effects. One developed severe vomiting and another had internal bleeding that required a blood transfusion.
"Although our radiation wasn't able to control the disease in everybody, if we had treated where they had recurred with further radiation, surgery or other types of ablation, they could have been rendered disease-free," Dr. Joseph Salama, who worked on the study, said in a telephone interview.
"Not all metastatic cancer is the same. In some people, more aggressive therapy can potentially be beneficial," Salama added.
Ten patients out of the original 29 are still alive, Salama said, and nine lived more than 20 months. They are treating more patients with higher doses of radiation now and of 51 patients treated so far, 15 are alive.
The researchers hope to find a genetic signature or some other way of identifying the patients who may hope to benefit from this radiation.
One key question is whether chemotherapy must first get rid of the tiny tumor seeds that spread and grow into metastases, Weichselbaum said.
"Most likely this will be used with the targeted therapies," he said.
New targeted drugs go straight for the mutation that causes the cancer, as opposed to traditional chemotherapy and radiation approaches that kill quick-growing cells, which include tumors but also healthy tissue.