Flash radiotherapy, a new technology that uses targeted proton beams, is safe and effective in relieving pain for terminal cancer patients, a new, small study suggests.
Flash radiotherapy delivers radiation at dose rates more than 300 times higher than those used in conventional radiation, does it in only about three-tenths of a second, and doesn't damage adjoining tissue. The hope, according to researchers, is that this technology will eventually replace current radiation therapy.
"It's kind of in its infancy, so nobody anywhere else in the world is doing it. Our trial is really the first one in the world to show that it's safe and effective," said researcher Dr. Emily Daugherty, an assistant professor of clinical radiation oncology at the University of Cincinnati Cancer Center.
"Someday, this may revolutionize how we treat patients with radiation, if we continue to see that it's just as effective and patients have minimal side effects," Daugherty added.
The research was funded by California-based Varian Medical Systems, which makes the new radiotherapy. Daugherty said studies are underway to test the technology on more people and eventually on cancerous organs.
She believes the results of this first trial might well mean that Flash would be at least as effective in treating most cancers as current radiotherapy, with no damage to surrounding tissue. Why Flash has the effect isn't clear, but it performed well in animal studies, Daugherty noted.
"This is a brand new way of delivering radiation that could potentially have practice-changing implications," she said. "Years down the road, perhaps we will treat patients' cancers faster and more effectively with fewer side effects."
For the trial, Daugherty and her colleagues used Flash radiotherapy on 10 patients whose cancers had metastasized to the bones. Treatments were delivered to 12 bone sites in patients' arms and legs.
This treatment uses a beam of protons instead of X-rays to destroy tumors without damaging healthy tissue and reduces the odds of long-term complications. Proton beams are only a few millimeters wide and are delivered through a crane that circulates 360 degrees around a patient.
Treatments took an average of 19 minutes. Over a median of five months of follow-up, side effects were mild and no different from conventional radiation. In all, for eight of 12 sites where Flash was delivered, patients reported pain relief, and in six of 12 sites, patients reported no pain. In four of 12 sites, patients experienced pain flare-ups.
Four patients experienced darkening skin tone, one had skin discoloration, two had mild limb swelling, two experienced itchy skin, one had fatigue, one had skin reddening and one experienced extremity pain.
These results are similar to those seen with conventional radiotherapy, but achieved with a single treatment, Daugherty noted.
The findings were presented Sunday at the American Society for Radiation Oncology annual meeting in San Antonio, Texas, to coincide with the online publication of the study in JAMA Oncology.
Dr. Anthony D'Amico, a professor of radiation oncology at Harvard Medical School in Boston, said this small trial is promising, but this technique could only be used to help relieve pain in terminally ill cancer patients, at least for now.
"It's an interesting technology that can provide treatment at a much quicker burst," he said. "It's one treatment as opposed to a week or two of treatments. The treatments are longer and do take anywhere from 15 to 30 minutes, as opposed to the usual five to seven minutes. But you get it all done in one day."
Still, it's too soon to tell if the pain responds to treatment as one would expect. "It's also too soon to tell whether or not those responses are durable," D'Amico said.
Right now, this treatment is for somebody who's not going to live three months, he said. "If you have somebody who's on the cusp of dying or transferring over to hospice, and you just want to give one treatment and quickly get them some pain relief for the next couple of months, this treatment might be helpful," D'Amico said.
Before Flash radiotherapy could be used to directly treat organs — such as the liver, pancreas, lung, prostate or brain — a lot more study is needed, he added.
"I'm optimistic because what you're really doing is increasing the dose rate and delivering it faster and more precisely. But you can't just assume because that's all you're doing, that it's equally effective," D'Amico said.
"I don't want people running out and saying I want the Flash radiotherapy to treat my prostate cancer in a week," he said. "We don't have the information to really prove that it's equally effective."
For more on radiation oncology, head to the American Society of Clinical Oncology.
SOURCES: Emily Daugherty, MD, assistant professor, clinical radiation oncology, University of Cincinnati Cancer Center, Ohio; Anthony D'Amico, MD, PhD, professor, radiation oncology, Harvard Medical School, Boston; presentation, American Society for Radiation Oncology annual meeting, San Antonio, Texas, JAMA Oncology, Oct. 23, 2022, online