The Quadrella: a novel approach to analyzing optimal outcomes after permanent seed prostate brachytherapy.

Abstract

To study a four-point combined analysis (Quadrella) of optimal outcome among patients treated with exclusive permanent seed prostate brachytherapy (PB), as defined by the likelihood of achieving disease control and preserving normal urinary, gastro-intestinal (GI) and sexual function. 384 patients with localized prostate cancer underwent PB at our institution with (125)I at a dose level of 144Gy. Subjects with erectile dysfunction who did not respond to medication were excluded. 281 patients with minimum 3-year follow-up were evaluated. Patients with concurrent biochemical progression-free survival (bPFS), absent urinary and GI toxicities (grade 0 toxicities according to CTCAE v 3.0) and preserved sexual potency (with our without medication) were classified as the Quadrella group. Among the 281 patients analyzed, the Quadrella was achieved in 49.1%, 48.0%, 50.4%, 41.7% and 65.2% in years 3-7, respectively. bPFS rates were 82.6-96.1%, corresponding potency rates were 63.6-82.3%, and normal urinary and GI function rates were 64.8-82.6% and 95-100%, respectively. By multivariate analysis, significant predictors of Quadrella were age (p=0.015), baseline IPSS (p=0.03) and time since PB (p=0.02). Urinary and sexual toxicity remained the most common reasons for excluding patients from a perfect outcome (Quadrella), defined by strict criteria. This analysis can be useful for subsequent comparison between treatment modalities.