Predictive Factors for Urinary Retention after Hdr Brachytherapy as Monotherapy for Prostate Cancer

Abstract

prostate volume (D90), has been used as a measure of implant quality. Although a D90O130 Gy is considered adequate, various studies have shown that a D90$140 Gy is associated with improved biochemical control. Previous studies have found that specific factors such as prostate volume, post implant prostatic edema, and the number of seeds can influence D90. Identifying factors that lead to suboptimal dosimetric outcomes is important in order to improve implant quality as well as clinical outcomes. In this retrospective analysis, we sought to study the effect of BMI on post implant dosimetric quality. Methods: After institutional approval, records of patients with nonmetastatic prostate cancer treated in Puerto Rico with LDR brachytherapy from 2008-2013 were reviewed. All patients were implanted with 12 ⁵I seeds to a prescription dose of 145 Gy. CT based dosimetry was performed 1 month after implant. Patients with at least 1 year of PSA follow-up were included. Factors predictive of adequate D90 coverage ($140Gy) were compared via Pearson chi square or Wilcoxon rank-sum test as appropriate. Factors evaluated included prostate volume, BMI, initial PSA, age, hormone use, percent of cores positive, risk group, tumor stage, and Gleason Score (GS). Results: One-hundred and four patients were included in this study, with 53 (51%) patients having a D90$140Gy. Majority of the patients were GS 6 (n590, 87%) with a median PSA of 4.7 ng/mL. The median age was 66 years of age, with a median prostate volume of 29cc. The only factor found to be predictive of D90 (!140Gy vs. $140Gy) was BMI (median: 28.3 vs. 26.7 kg/m2, p50.023). Prostate volume (p50.26), initial PSA (p50.236), age (p50.49), hormone use (p50.93), percent of cores positive (p50.95), risk group (p50.24), tumor stage (p50.66), and Gleason Score (p50.61) did not predict for D90. Conclusions: In this study we show that BMI is a significant pre-implant predictor of D90 (!140Gy vs. $140Gy ). Although other studies have reported that prostate volume also affects D90, our study did not find this correlation to be statistically significant; likely because all of our patients had a prostate volume ! 50 cc. Our study results may suggest that in order to achieve a D90$140 Gy in patients with higher BMIs, a D90 that is greater than the target post implant D90 should be planned. PO204Predictive Factors for Urinary Retention after Hdr Brachytherapy as Monotherapy for Prostate Cancer

Incidence of genitourinary complications following radiation therapy for localised prostate cancer

“…Similarly, the data on dose-related genitourinary dysfunction has been controversial, and whilst some studies suggested a correlation between dose to the bladder and genitourinary toxicity [ 23 , 24 , 35 – 41 ], this has generally been unconfirmed by other authors [ 26 ], including the current study in univariable regression analysis ( p = 0.4). This inconsistency may be due to confounding differences in treatment scheme (target volume, position during treatment, bladder volume variation, technique, dose), patient characteristics, grading scale and the length of follow-up [ 42 – 44 ].…”