Biochemical Failure Not a Surrogate for OS in Recurrent Prostate Cancer

By Leah Lawrence - July 20, 2022

Metastasis-free survival (MFS) is a strong surrogate endpoint for overall survival in men receiving salvage therapy for recurrence after prostatectomy, according to an analysis of data from the NRG Oncology/RTOG 9601 trial.

“The Intermediate Clinical Endpoints in Cancer of the Prostate (ICECaP) working group identified metastasis-free survival (MFS) as a valid surrogate for overall survival (OS) in men treated for localized prostate cancer when assessed at both the individual patient level and trial level,” according to study researchers.

However, this type of endpoint is disease specific, and it remained unknown if MFS was a valid surrogate endpoint in biochemically recurrent disease after radical prostatectomy.

NRG/RTOG 9601 randomly assigned 760 men with prostate cancer recurrence after prostatectomy to salvage radiation therapy with 2 years of placebo compared with bicalutamide. Intermediate clinical endpoints assessed including biochemical failure (BF) per NRG/RTOG 9601 (prostate-specific antigen nadir 1 0.3-0.5 ng/mL or initiation of salvage hormone therapy; [BF1]) and NRG/RTOG 0534 (prostate-specific antigen nadir12 ng/mL; [BF2]), distant metastasis (DM), and MFS (DM or death). Results were published in The Journal of Clinical Oncology.

The researchers found strong correlation between MFS and OS, moderate correlation between DM and OS, and weaker correlation between BF1 or BF2 and OS.

“Similar to men with intact localized prostate cancer, MFS appears to be the preferred surrogate for OS in men receiving postprostatectomy salvage radiation therapy, and biochemical end points should not be used at the present time as surrogates for OS in this setting,” the researchers concluded.

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