Contemporary salvage post prostatectomy radiotherapy: Early implementation improves biochemical control.

Abstract

The optimal time to commence salvage radiotherapy (SRT) for a rising PSA post radical prostatectomy is not known. We wished to assess the impact of index PSA (iPSA) level prior to SRT on rates of biochemical failure (BCF) post treatment. Patients referred to our institution for SRT for a rising PSA post surgery were accrued onto a prospective database. Baseline demographic data, tumour and treatment factors were collected including pathologic T and N stage, margin status, Gleason score (GS), lymphovascular space invasion (LVSI), use of androgen deprivation therapy (ADT) and time from surgery to salvage radiotherapy. Our endpoint was time to BCF. Between January 2008 and December 2013, 189 patients received SRT to a mean dose of 69.8Gy in 34 fractions using Intensity Modulated Radiotherapy (IMRT). Median follow-up was 50months. For patients with an iPSA of <0.2ng/mL (n=92), iPSA≥0.2 to <1.0ng/mL (n=75) and≥1.0ng/mL (n=22), rates of BCF at 5years were 28.3%, 44.3% and 73.7% respectively. Compared to the iPSA <0.2ng/mL group, the hazard ratios for time to BCF for an iPSA≥0.2 to <1.0ng/mL was 1.73 (P=0.05) and >1.0ng/mL was 3.1 (P=0.002). Factors predicting time to BCF on univariate analysis included iPSA, GS, T stage, PSA nadir post surgery and LVSI. On multivariate analysis, GS, iPSA, use of ADT, T stage, PSA post surgery nadir and margin status remained significant. Rising iPSA levels are associated with an increasing risk of biochemical failure after adjusting for known prognostic factors and early salvage post prostatectomy radiotherapy is recommended.