Interval to biochemical failure is prognostic for distant metastases after salvage radiation therapy for prostate cancer

We assessed the prognostic value of the interval to biochemical failure (IBF) after salvage radiation therapy (SRT) following radical prostatectomy (RP) for prostate cancer to identify patients at high risk for distant metastasis (DM), prostate cancer-specific mortality (PCSM), and overall mortality (OM). From 1991 and 2007, 222 men with T2a-4a, N0/X, M0 prostate cancer received SRT for a rising PSA after RP. Of these, 48 experienced BF. Univariate and multivariate analyses (UVA, MVA, respectively) included initial PSA; T-stage; RT dose; nadir PSA; risk group; IBF; time from surgery to SRT; seminal vesicle invasion; Gleason score; and PSA doubling time. Median follow-up from SRT was 67 months. The median IBF was 33 months (range, 4-96). On UVA, IBF < 12 or < 18 months and risk group predicted for DM, PCSM, and OM (p < 0.05). On MVA, IBF < 12 or < 18 months predicted for DM (HRs 36.1, 15.3, respectively, p = 0.02). The 5-year DM, PCSM, and OM rates for an IBF of < vs. a parts per thousand yen18 months were 50 vs. 17 %, 45 vs. 0 %, 53 vs. 0 %, respectively (all p < 0.01). Patients with IBF < 18 months are at significantly higher risk of DM and death from prostate cancer. The IBF may be used to guide patients and physicians considering the initiation of salvage ADT. Furthermore, an IBF < 18 months could be used to select "high-risk" patients for clinical trials investigating novel salvage systemic therapy.