Biochemical outcomes for patients with intermediate risk prostate cancer treated with I-125 interstitial brachytherapy monotherapy

Background and purpose: Routine use of I-125 interstitial brachytherapy (BT) alone in intermediate risk (IR) prostate cancer is controversial. It is often combined with external beam radiotherapy (EBRT). The biochemical outcome of a large cohort of only IR disease treated with BT monotherapy is reported. Materials and methods: Between 2003 and 2007, 615 patients with Memorial Sloan-Kettering Cancer Centre (MSKCC) defined IR disease (one risk factor only-T2b, or Gleason score (GS) 7, or raised initial PSA (iPSA) 10.1–20 ng/ml) were treated with BT monotherapy. ASTRO (3 consecutive rises) and Phoenix (nadir plus 2) criteria defined biochemical failure. Potential prognostic factors (pre- and post-implant dosimetric indices, GS 3 + 4 versus 4 + 3, androgen deprivation therapy (ADT)) were analysed. Results: Median follow-up was 5.0 years. Forty-three patients had stage T2b, 180 had raised iPSA, 392 had GS 7 disease. ADT was received by 108 patients. The 5-year biochemical no evidence of disease (bNED) rates are 87.3% (by ASTRO), 88.6% (by Phoenix). Stratification by risk factor (T2b, GS7, raised iPSA) demonstrated raised iPSA to have poorer outcome only by Phoenix criteria (p = 0.0002). Other potential prognostic variables were non-significant. Conclusion: Good rates of biochemical control can be achieved in the medium term with BT monotherapy in IR disease. Raised iPSA correlated with a poorer outcome