Pride or prejudice: Does Phoenix flatter radiation therapy?

PURPOSE: To compare disease-free survival (DFS) rates using a >0.4 ng/mL biochemical failure definition with the Phoenix (nadir+2 ng/mL) failure definition by analyzing a consecutive cohort of 1006 patients treated with low-dose-rate prostate brachytherapy (LDR-PB) monotherapy. METHODS AND MATERIALS: Data for first 1006 consecutive LDR-PB implants (1998-2003) were extracted from a prospective database. Patients had low- (58%) or intermediate (42%)-risk disease. Three months neoadjuvant and 3 months concomitant androgen deprivation therapy were used in 65% of cases. The Phoenix definition was modified to "unfail" patients who had a benign prostate-specific antigen (PSA) bounce. RESULTS: The median followup is 7.5 years. The median PSA at latest followup for disease-free patients was 0.04 ng/mL. The Phoenix definition yielded 5- and 10-year Kaplan Meier DFS estimates of 96.5 +/- 1.2% and 93.7 +/- 2.0%, respectively. Applying the >0.4 ng/mL threshold reduced these estimates to 94.4 +/- 1.6% and 88.8 +/- 3.0% (log rank, p = 0.015). CONCLUSIONS: Compared with Phoenix, applying a >0.4 ng/mL failure definition increased biochemical failure by similar to 2% at 5 years and similar to 5% at 10 years. These data show that Phoenix did not greatly exaggerate DFS estimates compared with a surgical-type threshold. However, this observation is a consequence of the exceptionally low residual PSA values characteristic of LDR-PB and cannot be generalized to other forms of radiation therapy. (c) 2014 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.