ASTRO 2020: Metastasis-Free Survival as Surrogate for Overall Survival in Recurrent Prostate Cancer
Posted: Friday, November 13, 2020
In a presentation during the virtual edition of the 2020 American Society for Radiation Oncology (ASTRO) Annual Meeting (Abstract 130), a team of investigators, led by William C. Jackson, MD, of the University of Michigan, reported that for patients receiving salvage radiotherapy following prostatectomy for recurrent prostate cancer, metastasis-free survival was a “strong surrogate” for overall survival. The investigators also concluded that biochemical failure was not a strong surrogate endpoint to determine overall survival.
“These findings highlight that the two-stage meta-analytic approach should be the preferred method when assessing surrogacy,” Dr. Jackson commented in an NRG Oncology press release.
This study was based upon an analysis of the phase III NRG Oncology clinical trial RTOG 9601 in which patients received salvage radiotherapy following prostatectomy. However, in this study, a two-condition approach was used to determine surrogacy. Thus, metastasis-free survival was strongly correlated with overall survival. Other endpoints were not significantly associated with overall survival: distant metastasis was only moderately correlated with overall survival, and biochemical failure was weakly correlated with overall survival.
The investigators analyzed the rates of clinical pain response, differences in acute and late toxicity, duration of pain response, and retreatment rates between the two groups. The overall clinical pain response rate was 97%; for those receiving high-dose radiotherapy, it was 98%, and for patients receiving low-dose radiotherapy, it was 95%. Acute toxicity appeared to be greater with the high-dose therapy than the low-dose therapy (24.5% vs. 9.5%).
“From this analysis, we believe that researchers should be cautious when inferring clinical benefit from studies utilizing biochemical failure as a surrogate for overall survival,” Dr. Jackson stated.
Disclosure: For full disclosures of the study authors, visit redjournal.org.