BACKGROUND: The ideal prostate-specific antigen (PSA) doubling time (PSADT) threshold for identifying patients at high-risk for poor clinical outcome following salvage radiation therapy (SRT) has not been well established.
We sought to assess what PSADT threshold is most clinically prognostic in this setting.
METHODS: 575 patients who received SRT at a single institution for biochemical recurrence after radical prostatectomy were retrospectively reviewed. We assessed the impact of pre-SRT PSADT on biochemical failure (BF), distant metastasis (DM), prostate cancer-specific mortality (PCSM), and overall mortality (OM). Kaplan-Meier methods, hazard ratio (HR) assessment, and Cox Proportional Hazard models were used to assess the discriminatory ability of various PSADT thresholds.
RESULTS: Sufficient data to calculate PSADTs were available for 277 patients. PSADT was prognostic for BF, DM, PCSM, and OM on univariate analysis regardless of threshold. HR assessment identified 6 months as a strong threshold. No statistically significant difference was observed in BF, DM, PCSM, or OM between patients with PSADT < 3 (n=40) and 3-6 months (n=61) or between 6-10 (n=62) and >10 months (n=114). However significant differences were seen in BF (HR:2.2, [95%CI: 1.4-3.5], p< 0.01) and DM (HR:2.2, [95%CI: 1.2-4.3], p=0.02) between a PSADT of 3-6 and 6-10 months. On multivariate analysis a PSADT < 6 months predicted BF (HR:2.0, [95%CI: 1.4-2.9], p=0.0001), DM (HR:2.0, [95%CI: 1.2-3.4], p=0.01), and PCSM (HR:2.6, [95%CI: 1.1-5.9], p=0.02).
CONCLUSIONS: A pre-SRT PSADT < 6 months was a strong predictor of outcomes in our data set, including PCSM. The most common nomogram for SRT uses a 10-month PSADT threshold for assigning points used to assess BF following SRT. If validated, our findings suggest that a PSADT threshold of < 6 months should be considered for stratification of patients in future clinical trials in this setting.
Written by:
Jackson WC, Johnson SB, Li D, Foster C, Foster B, Song Y, Schipper M, Shilkrut M, Sandler HM, Morgan TM, Palapattu GS, Hamstra DA, Feng FY. Are you the author?
Department of Radiation Oncology, University of Michigan, 1500 E. Medical Center Dr., Ann Arbor, MI 48105, USA.
Reference: Radiat Oncol. 2013 Jul 8;8:170.
doi: 10.1186/1748-717X-8-170
PubMed Abstract
PMID: 23835115
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