The performance characteristics of prostate-specific membrane antigen positron emission tomography improves with increasing prostate-specific antigen (PSA) level. This, coupled with insurance approval concerns if applied for too early, causes some physicians to delay post-radical prostatectomy salvage radiation therapy (sRT) until well after PSA failure, typically at PSA levels exceeding 0.30 ng/ml.
To determine whether such a delay increases mortality risk, a multinational group led by researchers from Dana-Farber Brigham Cancer Center studied radical prostatectomy and lymph node specimens from 25,551 patients with no more than one high-risk factor (prostatectomy Gleason score of 8–10 or evidence at surgery of extension of the cancer outside the prostate). They sought to identify a PSA level above which initiating sRT is associated with increased mortality risk.
The research team used multivariable Cox regression analysis beginning at a PSA level of 0.10 ng/mL and in 0.05 increments up to 0.50 ng/mL versus at or below that level. The model was adjusted for age at and year of surgery, established prostate cancer prognostic factors, institution, and time-dependent use of androgen deprivation therapy.
The study found that after a median follow-up of six years, patients who received sRT at a PSA level higher than 0.25 ng/mL had approximately a 50 percent higher risk of death compared with those who received sRT when the PSA was at or below 0.25 ng/ML.
"At Dana-Farber Brigham, we tend to be more medically conservative and not allow these restraints to drive patients to a lower cure rate," said principal investigator Anthony Victor D'Amico, MD, PhD, chief of Genitourinary Radiation Oncology, Dana-Farber Brigham Cancer Center. "Normally, we would want to start sRT at a PSA level of 0.2, or even 0.1 ng/ml in most cases, to decrease the risk of the cancer metastasizing or becoming resistant to existing salvage treatments such as radiation and androgen deprivation therapy and to maximize curability."
