PSA trend before and during salvage radiation therapy: Prognostic factor for biochemical control.

Abstract

e15048 Background: Post-prostatectomy patients undergoing salvage radiation therapy (S-RT) has a high rate of biochemical recurrence (BR). Early initiation of androgen deprivation therapy has been shown to improve outcome in this cohort. We hypothesize that measuring the PSA trends during S-RT has predicitive value in defining a cohort of patients at higher risk of BR. Methods: Sixty-five patients with BR (ASTRO definition) were enrolled in this IRB-approved study. Patients receiving ADT prior to S-RT or adjuvant S-RT were excluded. Patients were treated by a single radiation oncologist using IMRT to a dose of 66 Gy. PSA was measured prior to the initiation of S-RT and during S-RT at two week intervals. BR after S-RT was defined as PSA value > or = 0.1 ng/ml above the post-S-RT PSA nadir confirmed by a second measurement that, or no response in PSA, or the initiation of ADT. Univariate Kaplan-Meier (KM) analysis with log rank test and Cox regression multivariate hazard ratio (HR) was used to analyze the probability of BR for the variables listed in the table below. Results: The BRFS, overall survival, and PCa specific survival in this group at a median follow-up of 40 months (m) is 71.2%, 95.5% and 97% respectively with a median time to BR of 16.4m. 90% of the patients with a decreasing PSA trend during S-RT were free of BR compared to only 15% of patients with an increasing PSA trend during S-RT (p<0.001; cox HR 0.08 [0.029<95CI<0.216 ]). In KM analysis pre-S-RT PSA velocity of <0.075/m also predicted BR (p=0.01; cox HR 0.252 [0.81<95%CI<0.782]). In multivariate Cox regression modeling, S-RT PSA trend remained significant with p<0.001 and HR of 0.044 (0.008<95%CI<0.214). Conclusions: Increasing PSA during S-RT or pre-S-RT PSA velocity>0.075/m are predictive of biochemical failure. Identifying these patients at an earlier stage of their management may be beneficial for the addition of systemic therapy leading to an improved outcome. N %BR KM log rank p Total patient # 65 28.8 Pre-treatment PSA >10 46 26.1 0.4 Pathology on Ppr G>6 47 36 0.031 VI 16 25 0.32 ECE 19 36.8 0.8 PNI 29 41.3 0.083 Margin + 38 23.7 0.23 S-RT decreasing PSA trend 14 85.7 <0.001 Pre-S-RT PSA nadir >0.2 24 37.5 0.48 Pre-S-RT PSA velocity>0.075/m 13 46 0.01 Pre-S-RT PSA >1 9 33 0.45 No significant financial relationships to disclose.