Prostate cancer accounts for an estimated 30,000 deaths each year in the U.S., according to the study authors, and is the most common cancer to afflict men as well as the third most common cancer overall. It is possible that using complete metastatic ablation could be an alternative to early androgen deprivation therapy (ADT) initiation.
The researchers reported the outcomes of the Observation vs Stereotactic Ablative Radiation for Oligometastatic Prostate Cancer (ORIOLE) study, a phase 2 randomized trial encompassing patients from three U.S. radiation treatment facilities affiliated with a university hospital between May 2016 and March 2018. Patients with recurrent hormone-sensitive prostate cancer were eligible for inclusion; 54 patients with one to three metastases who did not have a six-month history of ADT were randomized 2:1 to either receive SABR or be observed. The main outcome measures was six-month progression, measured by prostate-specific antigen level increase, conventional imaging, and symptoms; all-cause ADT initiation; and death. Secondary outcomes included toxic effects of SABR, six-month local control with SABR, progression-free survival, quality of life measured by the Brief Pain Inventory (Short Form), and concordance between conventional imaging and prostate-specific membrane antigen (PSMA)–targeted positron emission tomography in the identification of metastatic disease.
SABR Superior to Observation
In the SABR group, the median (range) age was 68 (61 to 70) years; median age (range) in the observation group was 68 (64 to 76) years. At six months, progression was observed in 19% of SABR patients and 61% of observation patients. Median progression-free survival was also improved in SABR patients (not reached vs. 5.8 months; hazard ratio=0.30; 95% confidence interval, 0.11 to 0.81; P=0.002). At six months, total consolidation of PSMA radiotracer-avid disease lowered new lesion risk (16% vs. 63%; P=0.006). There were no grade 3 or greater toxic effects.
The researchers summarized, “Treatment with SABR for oligometastatic prostate cancer improved outcomes and was enhanced by total consolidation of disease identified by PSMA-targeted positron emission tomography. SABR induced a systemic immune response, and baseline immune phenotype and tumor mutation status may predict the benefit from SABR. These results underline the importance of prospective randomized investigation of the oligometastatic state with integrated imaging and biological correlates.”