Background: In general population studies, obesity has been associated with risk of high-grade prostate cancer, but little is known about obesity and future prostate cancer risk among men with an initial benign biopsy of the prostate; a high-risk population. Methods: Within a cohort of 6,692 men followed up after a biopsy or transurethral resection of the prostate (TURP) with benign findings, a nested case-control study was conducted of 494 prostate cancer cases and controls matched on age, race, follow-up duration, biopsy versus TURP and date of procedure. Body mass index at the time of the initial procedure was abstracted from medical records, and initial biopsy specimens were reviewed for the presence of prostatic intraepithelial neoplasia (PIN). Results: Obesity was associated with the presence of PIN in the initial benign specimen [OR = 2.15; 95% confidence interval (CI) 1.13-4.11]. After adjustment for the matching variables, family history of prostate cancer, prostate-specific antigen (PSA) levels at the initial procedure, the number of PSA tests and digital rectal examinations during follow-up, obesity (OR = 1.57; 95% CI, 1.07-2.30) at the time of the initial procedure was associated with prostate cancer incidence during follow-up. Risk associated with obesity was confined to cases with follow-up less than 1,538 days, the median duration of follow-up among cases (OR = 1.95; 95% CI, 1.09- 3.48). Conclusions: Obesity is associated with the presence of PIN in benign specimens and with future prostate cancer risk after an initial benign finding. Impact: Obesity may be a factor to consider when planning clinical follow-up after a benign biopsy. Cancer Epidemiol Biomarkers Prev; 22(5); 898-904.
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