According to a recent article in Medical Life Sciences, the radiation dose rates used by the new FLASH radiotherapy are over three hundred times more intense than conventional treatments. The new regimen delivers its radiation dose in a fraction of a second.
Normal radiation therapy injures cells through the destruction of the genetic material controlling the way cells divide and grow. As noted, cancerous and healthy cells are both subject to injury. Yet the goal of normal radiation treatment is to leave healthy cells unharmed. Normal cells are able to repair some of the radiation damage.
Thus far the regimen (the FLASH RT effect) has proven to reduce harmful side effects to healthy tissue in areas surrounding the tumor.
About the Study
The technology has been tested on animals. The current small study FAST-01 (NCT04592887) involves patients with bone cancer. This trial is the first to test FLASH RT in humans The findings are being presented today at the ASTRO Annual Meeting.
In the FAST-01 study, ten patients (21 to 81 years of age) were given extremely high dose radiation. Each patient was found to have several painful metastases in their arms or legs and was treated at these sites.
Proton vs. Electron Beams
As aforesaid, the FLASH RT study involves patients with bone cancer as electron beams do not penetrate deeply into tissue. The FDA approved the study based on the use of electron beams in order to test the safety of the procedure before targeting organs, such as the lungs, the brain, and the gastrointestinal area.
Clinical trials will not be authorized until studies confirm that radiation using a high dose rate is safe in areas of the body that are less sensitive than major organs.
Electron beam therapy is unlike protons or photons as it treats extremely shallow tumors. Lead Author of the study, Dr. Emily Daugherty, said that the study found that FLASH RT with protons reduces the painful side effects of conventional radiation.
Dr. John Breneman, the principal investigator of the study, added that the ultra-high dose emitted by FLASH RT seems to cause less injury to normal tissue. Therefore, the researchers used higher doses of radiation successfully targeting the more resistant tumors but with fewer side effects.
A follow-up to the Study
The researchers measured the patients’ pain, use of pain medication, and other adverse events starting at the first treatment and continuing at intervals thereafter for a total of thirteen months. The median time for follow-up was 4.8 months.
Dr. Daugherty further stated that the researchers used the FLASH radiation dose but the patients’ experience was the same as if they were given conventional radiation. The difference is that the treatment is of a shorter duration.
About Study Results
Of the ten patients in the study, seven patients reported a complete or partial reduction in pain. Twelve areas were treated and six patients reported that they had complete relief for six sites and partial relief for two other sites. Temporary painful flares appeared in four of the twelve sites.
Patients experienced mild side effects as a result of the treatment such as darkening skin tone (hyperpigmentation), swelling or puffiness (limb edema), itchy skin (pruritis), and one patient reported extremity pain.
Currently, the FAST-02 trial (NCT05524064) is enrolling patients with thoracic bone metastases. The thoracic bone is between the cervical spine and the lumbar spine.
Further, the research team is preparing to conduct a study enrolling patients with metastases that are close to the heart and lungs.