title: The impact of body mass index on dosimetric quality in low-dose-rate prostate brachytherapy.
abstract: OBJECTIVE
  Low-dose-rate (LDR) brachytherapy has been established as an effective and safe treatment option for men with low and intermediate risk prostate cancer. In this retrospective analysis, we sought to study the effect of body mass index (BMI) on post-implant dosimetric quality.
  
  
  METHODS
  After institutional approval, records of patients with non-metastatic prostate cancer treated in Puerto Rico with LDR brachytherapy during 2008-2013 were reviewed. All patients were implanted with125I seeds to a prescription dose of 145 Gy. Computed tomography (CT) based dosimetry was performed 1 month after implant. Patients with at least 1 year of prostate-specific antigen (PSA) follow-up were included. Factors predictive of adequate D90coverage (≥ 140 Gy) were compared via the Pearson χ2or Wilcoxon rank-sum test as appropriate.
  
  
  RESULTS
  One-hundred and four patients were included in this study, with 53 (51%) patients having a D90≥ 140 Gy. The only factor associated with a dosimetric coverage detriment (D90< 140 Gy) was BMI ≥ 25 kg/m2(p= 0.03). Prostate volume (p= 0.26), initial PSA (p= 0.236), age (p= 0.49), hormone use (p= 0.93), percent of cores positive (p= 0.95), risk group (p= 0.24), tumor stage (p= 0.66), and Gleason score (p= 0.61) did not predict D90.
  
  
  CONCLUSIONS
  In this study we show that BMI is a significant pre-implant predictor of D90(< 140 Gy vs. ≥ 140 Gy). 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 suggests that in patients with higher BMI values, more rigorous peri-implant dosimetric parameters may need to be applied in order to achieve a target D90> 140 Gy.
authors.affiliation: Radiation Oncology, H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL, USA.
authors.forename: Michelle I
authors.initials: MI
authors.lastname: Echevarria
authors.affiliation: Radiation Oncology, H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL, USA.
authors.forename: Arash O
authors.initials: AO
authors.lastname: Naghavi
authors.affiliation: Radiation Oncology, H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL, USA.
authors.forename: Puja S
authors.initials: PS
authors.lastname: Venkat
authors.affiliation: Radiation Oncology, H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL, USA.
authors.forename: Yazan A
authors.initials: YA
authors.lastname: Abuodeh
authors.affiliation: Radiation Oncology, Hospital Oncológico, HIMA San Pablo, Caguas, Portorico.
authors.forename: Carlos
authors.initials: C
authors.lastname: Chevere
authors.affiliation: Radiation Oncology, H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL, USA.
authors.forename: Kosj
authors.initials: K
authors.lastname: Yamoah
keywords: BMI; low-dose-rate brachytherapy; prostate cancer; seeds