Abstract
BackgroundProstate-specific antigen (PSA) nadir + 2 ng/mL, also known as the Phoenix definition, is the definition most commonly used to establish biochemical failure (BF) after external beam radiotherapy for prostate cancer management. The purpose of this study is to compare BF rates between permanent prostate brachytherapy (PPB) and radical retropubic prostatectomy (RRP) as a function of PSA nadir plus varying values of X and examine the associated implications.Methods and materialsWe retrospectively searched for patients who underwent PPB or RRP at our institution between 1998 and 2004. Only primary patients not receiving androgen-deprivation therapy were included in the study. Three RRP patients were matched to each PPB patient on the basis of prognostic factors. BF rates were estimated for PSA nadirs + different values of X.ResultsA total of 1,164 patients were used for analysis: 873 in the RRP group and 291 in the PPB group. Patients were equally matched by clinical stage, biopsy Gleason sum, primary Gleason grade, and pretherapy PSA value. Median follow-up was 3.1 years for RRP patients and 3.6 years in the PPB group (P = .01). Using PSA nadir + 0.1 ng/mL for the definition of BF, the 5-year BF rate was 16.3% for PPB patients and 13.5% for RRP patients (P = .007), whereas at nadir + 2 ng/mL or greater, the BF rates were less than 3% and were indistinguishable between PPB and RRP patients.ConclusionsIn a cohort of well-matched patients who had prostatectomy or brachytherapy, we examined BF as a function of nadir + X, where X was treated as a continuous variable. As X increases from 0.1 to 2.0 ng/mL, the BF curves converge, and above 2.0 ng/mL they are essentially indistinguishable. The data presented are of interest as BF definitions continue to evolve.
Highlights
Prostate-specific antigen (PSA) nadir + 2 ng/mL, known as the Phoenix definition, is the definition most commonly used to establish biochemical failure (BF) after external beam radiotherapy for prostate cancer management
Using PSA nadir + 0.1 ng/mL for the definition of BF, the 5-year BF rate was 16.3% for permanent prostate brachytherapy (PPB) patients and 13.5% for retropubic prostatectomy (RRP) patients (P = .007), whereas at nadir + 2 ng/mL or greater, the BF rates were less than 3% and were indistinguishable between PPB and RRP patients
In a cohort of well-matched patients who had prostatectomy or brachytherapy, we examined BF as a function of nadir + X, where X was treated as a continuous variable
Summary
Prostate-specific antigen (PSA) nadir + 2 ng/mL, known as the Phoenix definition, is the definition most commonly used to establish biochemical failure (BF) after external beam radiotherapy for prostate cancer management. In 1997, the American Society for Therapeutic Radiology and Oncology (ASTRO) defined BF after external beam radiotherapy (EBRT) as 3 consecutive increases in PSA after treatment; the date of failure is set (backdated) at the midpoint between the time of PSA nadir and the first of the 3 increases [2] This definition allowed for comparison of outcomes between treatment methods and institutions, but it had limitations. In 2006, using data from a multi-institutional database of patients treated with EBRT, ASTRO revised the definition of BF to be a PSA value 2 ng/mL greater than the patient’s absolute PSA nadir (“nadir + 2 ng/mL”) after EBRT [5] This definition, known as the Phoenix definition, has been shown to have improved sensitivity and specificity in predicting subsequent clinical failure after radiotherapy as compared with the ASTRO definition and many other definitions [6,7,8,9]. Another advantage of the new definition is that it tends to limit the number of patients who are designated as having BF because it does not include those who merely experience a benign PSA “bounce” [10,11]
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