A new study, conducted across 13 medical centers in Australia and New Zealand, strengthens the case for radiation therapy as a treatment for cancer that has begun to spread throughout the body. In the randomized phase II trial, patients with up to three lung metastases who were treated with stereotactic ablative radiotherapy (SABR, also known as stereotactic body radiation therapy, or SBRT) fared equally well whether their radiation was delivered in one or four treatment sessions. Findings of the SAFRON II trial (NCT01965223) will be presented today at the American Society for Radiation Oncology (ASTRO) Annual Meeting.
“I think the future of radiation oncology could be these ultra-short treatments,” said lead investigator Shankar Siva, PhD, an associate professor of radiation oncology and head of the SBRT program at the Peter MacCallum Cancer Centre in Melbourne, Australia. “Our results indicate that SBRT can be a safe and effective treatment for patients whose cancer has spread to their lungs, even when it’s delivered in a single session.”
Up to half of all cancers that start elsewhere in the body spread to the lungs, the second most common site for metastases to occur. These types of tumors are typically treated with drug therapy, but typically the tumors become resistant and come back. In recent years, research has shown that SBRT can help these patients to live longer without their cancer returning.
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"For patients with a limited number of metastases, recent studies have shown that there can be long-term survivors with the use of SBRT," said Dr. Siva. "These studies tend to be smaller institutional series with a wide variety of SBRT regimens, so we designed our trial to test the safety and effectiveness of SBRT in a more robust fashion."
In this phase II TROG Cancer Research trial, Dr. Siva and his team randomized 90 patients into two treatment arms: half received a single fraction of 28Gy and the other half received a biologically-equivalent regimen of four fractions of 12Gy each. Each patient had up to three lung metastases from primary tumors in other sites, most commonly colorectal cancer (47%).
A total of 37 patients in each treatment group were eligible for safety analyses at one year after treatment. In the cohort who received a single treatment, two patients had grade three side effects, including fatigue, loss of breath and chest pain; no patients experienced grade four or five side effects (i.e., hospitalization or death). In the cohort who received four SBRT treatments, one patient died after experiencing pneumonitis within three months of treatment; there were no grade three or four events. Dr. Siva explained that the events on the single-fraction arm lasted less than three months and that his team found undiagnosed interstitial lung disease in the patient who died on the four-fraction arm.