Toxicity and early treatment outcomes in low- and intermediate-risk prostate cancer managed by high-dose-rate brachytherapy as a monotherapy

Abstract

Purpose To determine the acute and late genitourinary (GU) and gastrointestinal (GI) toxicity and present short-term biochemical no evidence of disease (bNED) rates after high-dose-rate brachytherapy (HDR-B) monotherapy. Methods and Materials Between October 2003 and June 2006, 36 patients with low (28) and intermediate (8) risk prostate cancer (PCA) were treated by HDR-B monotherapy. All patients received one implant and four fractions of 9.5 Gy within 48 h for a total prescribed dose (PD) of 38 Gy. Five patients received hormonal therapy (HT). Median age was 63.5 years and median followup was 3 years (range, 0.4–4 years). Toxicity was scored according to the CTCAE version 3.0. Biochemical failure was defined according to the Phoenix criteria. Results Acute and late Grade 3 GU toxicity was observed in 1 (3%) and 4 (11%) patients, respectively. Grade 3 GI toxicity was absent. The three- year bNED survival rate was 100%. The sexual preservation rate in patients without HT was 75%. Late Grade 3 GU toxicity was associated with the planning target volume (PTV) V100 (% PTV receiving ≥100% of the PD; p = 0.036), D90 (dose delivered to 90% of the PTV; p = 0.02), and the urethral V120 (urethral volume receiving ≥120% of the PD; p = 0.043). The urethral V120 was associated with increased PTV V100 (p < 0.001) and D90 (p = 0.003). Conclusions After HDR-B monotherapy, late Grade 3 GU toxicity is associated with the urethral V120 and the V100 and D90 of the PTV. Decrease of the irradiated urethral volume may reduce the GU toxicity and potentially improve the therapeutic ratio of this treatment.