The impact of obesity on the diagnosis of prostate cancer using a modern extended biopsy scheme

Abstract

Purpose: The effect of obesity on prostate cancer detection and behavior remains uncertain. We evaluated the impact of obesity, as measured by body mass index, in a case series of 500 consecutive men who underwent a modern 10 to 12 core biopsy approach.

Materials and methods: We retrospectively reviewed the records of a consecutive series of 500 men who underwent transrectal ultrasound guided prostate biopsy using a 10 to 12 core biopsy scheme. Variables, including patient age, prostate specific antigen, prostate specific antigen density, digital rectal examination findings, transrectal ultrasound prostate volume and biopsy outcome, including grade, were compared to anthropometric measures, including body mass index.

Results: Of the men 26% were obese according to body mass index (greater than 30 kg/m(2)). A total of 223 men (45%) had a positive biopsy. Obese men were younger (62.0 vs 63.8 years), had a larger prostate (57.7 vs 47.8 cc) and were less likely to have any abnormality on digital rectal examination (19.6% vs 30.8%). Obese men were also less likely to have a positive biopsy based on chi-square analysis (38.8% vs 46.2%). On statistical modeling for the OR in nonobese vs obese men there was a trend toward lower detection based on crude and age adjusted ORs but not on multivariate OR controlling for age, prostate specific antigen and prostate volume. In addition, when examining for high grade disease (Gleason 4 + 3 or greater), no differences were observed on OR modeling. In men with negative biopsies those who were obese vs nonobese had a larger prostate volume and trended toward a higher median prostate specific antigen and age. These differences and trends were not observed in obese men with positive biopsies.

Conclusions: Of men undergoing prostate biopsy using a modern extended biopsy scheme obese men were younger, had a larger prostate and were less likely to have abnormal digital rectal examinations. Although some trends toward a lower detection rate in obese men were observed, such differences were not observed on multivariate analysis, nor were any differences observed in the incidence of higher grade tumors, thus questioning the effect of obesity on prostate cancer detection and behavior in our cases series.