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Stronger Association between Obesity and Biochemical Progression after Radical Prostatectomy among Men Treated in the Last 10 Years

Authors' Affiliations: Departments of ¹ Urology, and ² Pathology, The Johns Hopkins School of Medicine; ³ Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins Medical Institutions; and ⁴ Department of Epidemiology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland

Requests for reprints: Stephen J. Freedland, The James Buchanan Brady Urological Institute, The Johns Hopkins Medical Institutions, 600 North Wolfe Street, Baltimore, MD 21287-2101. Phone: 410-955-2520; Fax: 410-502-9336; E-mail: sfreedl1{at}jhmi.edu.

Background: Prior prospective cohort studies found that obesity was associated with increased risk of prostate cancer death. However, in the last 20 years dramatic changes in both the extent of obesity and prostate cancer screening and treatment have occurred. Whether the association between obesity and aggressive disease has changed as a result of these temporal changes is unclear.

Methods: The study population consisted of 2,832 men treated by anatomic radical retropubic prostatectomy between 1985 and 2004 by a single surgeon. We evaluated the associations of obesity (body mass index 30 kg/m²)with tumor stage and grade using logistic regression and with biochemical progression using Cox proportional hazards regression. We examined whether these associations have changed over the last 20 years.

Results: On multivariable analysis, the strength of the positive association between obesity and high-grade disease increased over time whereas the strength of the positive association between obesity and positive surgical margins decreased over time. The strength of the positive association between obesity and extraprostatic extension fluctuated over time, although the strongest and only statistically significant association was among men treated since 2000. The association between obesity and biochemical progression was strongest among men treated since 1995 (relative risk, 1.90; 95% confidence interval, 1.09-3.30; P = 0.02).

Conclusions: In the current study, with the exception of positive surgical margins, the positive association between obesity and high-grade disease, advanced stage, and biochemical progression after radical retropubic prostatectomy was in general strongest among men treated in the last 10 years. The reasons for these findings are not clear, although factors possibly related to prostate-specific antigen–based screening and/or other temporal changes in prostate cancer diagnosis and treatment may play a role.

Key Words: Genitourinary cancers: prostate • Descriptive, Risk Factor, and Methodological Studies • Diet, alcohol, smoking, and other lifestyle risk factors • Methodology, modeling, and biostatistics

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