Associated morbidity related to high dose rate afterloading brachytherapy and neoadjuvant androgen deprivation as a boost to conventional external beam radiation therapy for initial and local advanced prostate cancer

Abstract

4746 Background: Verify acute and late intestinal (GI) and urological (GU) morbidity when high dose rate brachytherapy (HDR) was used as boost to conventional external beam radiatiotherapy (EBRT) in prostate cancer Methods: From 03/97 to 10/00 108 patients with biopsy proven adenocarcinoma Gleason scored, 1992 AJCC clinical stage T3a or lesser were treated with a course of EBRT 6MV photons to a median dose of 46Gy to the prostate only. For HDR-BT treatments patients were grouped into four groups: low risk (LR) without or with neoadjuvant total androgen deprivation (AD) and high risk (HR) without or with neoadjuvant AD. LR encompassed patients who presented GS ≤ 6, initial PSA ≤ 10ng/ml and or prostate volume ≤35 cc. They received 16Gy (4Gy fractions, BID) HDR. The remaining patients were grouped into HR and received 20Gy (5Gy fractions, BID) HDR. Biological effective doses (BED) for acuter and late responding tissue were calculated and matched with late gastro-intestinal (GI) and urological (GU) morbidity. Results: Median age of patients was 68 years old (range 47 to 83) and median follow-up 42 months (range 24 to 72). Acute GU and GI morbidity G1–2 were seen in 18.5% (20/108) and 10.2% (11/108) of patients. Late GI and GU morbidity G1–2 were seen in 12% (13/108) and 4.6 (5/108) of patients. Three patients (2,7%) developed G3 GU late morbidity, as urethral strictures (UR). When we stratified age for > or < 65 years with presence of NAAD (p=0.0234) and active length of needles greater than 3.5cm (p=0.0395) there was a statistically significant correlation with incidence of UR. Otherwise stratification by age older than 65 years and PUTV more than 35 cc (0.0593) did not have a statically significant correlation. On multivariate analysis by Cox regression age older than 65 years was the only predictive factor for the development of UR (p = 0.027). Conclusions: the most important antages in HDR-BT are the capability of on-line dosimetry and quality control. There is relative low incidence of GU and GI morbidity, but we still need to wait for results of phase III open trials that analyses HDR-BT and conformal therapy. No significant financial relationships to disclose.