1. ¹Department of Surgery, Veterans Affairs Medical Center, Durham, NC, USA
2. ²Division of Urologic Surgery, Department of Surgery and the Duke Prostate Center, Duke University School of Medicine, Durham, NC, USA
3. ³Department of Pathology, Duke University School of Medicine, Durham, NC, USA

Correspondence: Dr SJ Freedland, Division of Urologic Surgery, Duke University School of Medicine 571 Research Drive, Room 455, Box 2626 DUMC, Durham, NC 27710, USA. E-mail: steve.freedland@duke.edu

Received 9 December 2008; Revised 17 February 2009; Accepted 19 February 2009; Published online 7 July 2009.

Abstract

Obesity is associated with increased risk of positive surgical margins and prostate specific antigen (PSA) recurrence among men undergoing radical prostatectomy. To what degree positive margins contribute to poorer outcome is unclear. Thus, we sought to examine the association between body mass index (BMI) and more objective measures of tumor aggressiveness, tumor grade and size. We carried out a retrospective analysis of 2302 patients treated with radical prostatectomy at the Duke Prostate Center from 1988–2007. Tumor volume was calculated by multiplying prostate weight by percent of specimen involved with cancer. Associations between BMI and tumor volume and high-grade disease (Gleason4+3) independent of pre-operative clinical characteristics of age, race, PSA, clinical stage, biopsy Gleason sum, and year of surgery were assessed using linear and logistic regression, respectively. Mean and median BMI among all subjects was 28.1 and 27.6 kg m^–2, respectively. Increased BMI was significantly associated with younger age (P<0.001), black race (P<0.001), more recent year of surgery (P<0.001), and positive surgical margins (P<0.001). After adjusting for multiple clinical pre-operative characteristics, higher BMI was associated with a greater percent of the prostate involved with cancer (P=0.003), increased tumor volume (P<0.001), and high-grade disease (P=0.007). Men with a BMI 35 kg m² had nearly 40% larger mean tumor volumes than normal weight men (5.1 versus 3.7 cc), after adjustment for multiple clinical characteristics. In this study, obese men undergoing radical prostatectomy had higher-grade and larger tumors, providing further evidence that obese men undergoing radical prostatectomy have more aggressive prostate cancers.