ASTRO 2019: SABR Versus Observation for Men With Oligometastatic Prostate Cancer
Posted: Friday, October 4, 2019
Results from the phase II ORIOLE trial, presented at the 2019 American Society for Radiation Oncology (ASTRO) Annual Meeting in Chicago (Abstract LBA3), suggest that stereotactic ablative radiation therapy (SABR) is an effective and safe option for men with oligometastatic prostate cancer who are considering delaying hormone-suppression therapy. Ryan Phillips, MD, of the Johns Hopkins School of Medicine, Baltimore, and colleagues observed that SABR “affords significant benefits” in disease progression and induced an immune system response not prevously found in this type of cancer.
“This is the first bit of evidence that I’m aware of showing that SABR can induce a systemic imune response in patients with prostate cancer,” said principal investigator Phuoc Tran, MD, PhD, of the Johns Hopkins Kimmel Cancer Center, in an ASTRO press release. “These are probably the most robust, sensitive, and controlled observations that SABR can excite a systemic immune response.”
In this randomized trial, the investigators enrolled 54 patients with recurrent hormone-sensitive oligometastatic prostate cancer to receive either SABR therapy or observation. At 6 months, the authors observed disease progression in 19% of patients treated with SABR, compared with 61% of those who were not. For patients treated with SABR, the median progression-free survival was not reached, whereas those in the observation group exhibited a median progression-free survival of 5.8 months.
Of the 35 patients treated with SABR who also received prostate-specific membrane antigen–based positron-emission tomography–computed tomography imaging, those with total consolidation of radiotracer-avid disease were less likely to develop new lesions than those with subtotal consolidation (16% vs. 63%, respectively) and also had a significantly longer median progression-free survival time (unreached vs. 11.8 months, respectively).
“Cancer of the prostate is a tumor that does not typically incite a response from the immune system, so seeing this response is exciting,” Dr. Tran noted.
Disclosure: The study authors’ disclosure information may be found at redjournal.org.