Long-Term Outcomes Analysis of Low Dose Rate Brachytherapy (LDR-BT) in Clinically T3 High-Risk Prostate Carcinoma

Abstract

Prior utilization and reporting of outcomes with Low Dose Rate Prostate Brachytherapy (LDR-BT) in patients with prostatic extracapsular extension (T3a) and/or seminal vesicle invasion (T3b) has been limited. Herein, we report the long term clinical outcomes data for patients with cT3a/b disease receiving LDR-BT based treatment approaches and hypothesize that these approaches will achieve acceptable long term biochemical control rates. 99 men (median age: 69.4 years) with cT3a (75%) or cT3b (25%) high-risk prostate adenocarcinoma received definitive LDR-BT (29%) or LDR-BT boost following external beam (EBRT) with I-125 or Pd-103 at a single institution between 1998 and 2007. Median PSA at diagnosis was 11.4 ng/ml with 51% and 49% of men having initial gleason scores of <7 and 8-10, respectively. All patients receiving definitive LDR-BT refused receipt of EBRT. 86% of patients received Androgen Deprivation Therapy. Sources were delivered via a pre-planned, template-based, pre-loaded needle technique. Biochemical relapse free survival (BRFS), Prostate Cancer Specific Mortality (PCSM), and Overall Survival (OS) were calculated using the Kaplan-Meier method with the Phoenix definition (nadir plus 2ng/ml) as definition of failure. Outcomes are reported as estimates (+/- standard error). Cox-Regression analysis was used to compare outcomes between T3a & T3b disease, initial Gleason Scores (6-10) as well as among stratification of initial PSA (iPSA: <10ng/ml, 10-20, >20), and Percent Core Positive rates (<25%, 25-50%, 50-75%, >75%). With a median follow up time of 6.9 years, 7 year BRFS was 65.2% (+/- 5.6%), 7 year PCSM was 9.9% (+/- 3.6%), and 7 year OS was 77.9% (+/- 4.7%) for all patients. No significant difference in BRFS, PCSM or OS rates was present between T3a or T3b disease, initial gleason score, iPSA stratification or percent core positive rates. Men with cT3 high-risk disease achieve excellent biochemical control and survival outcomes with use of LDR-BT based treatment techniques, suggesting that the presence of T3 disease should not be a contraindication to use of LDR-BT. No significant difference in outcomes is present based on initial tumor related characteristics at this follow up period.