Elsevier

Urology

Volume 76, Issue 5, November 2010, Pages 1268.e1-1268.e6
Urology

Basic and Translational Science
Body Mass Index Adjusted Prostate-specific Antigen and Its Application for Prostate Cancer Screening

https://doi.org/10.1016/j.urology.2010.04.060Get rights and content

Objectives

The prostate cancer prevention trial (PCPT) prostate cancer risk calculator was developed to aid physicians in counseling men for consideration of prostate biopsy based on prostate-specific antigen (PSA) and other clinical risk factors. This study investigated the role of body mass index (BMI) in this assessment.

Materials and Methods

BMI category was defined as <25 (under/normal weight), 25.0-29.9 (overweight), 30.0-34.9 (obese [OB] I), 35.0-39.9 (OB II), and ≥40 (OB III). BMI-adjusted PSA for a man was determined by multiplying his PSA to the ratio of the geometrical mean of PSA for BMI <25 to the geometrical mean of PSA for his BMI category. Operating characteristics of PSA and BMI-adjusted PSA were compared with PCPT risks using area underneath the receiver operating characteristic curve (AUC). Statistical tests of differences between AUCs for different diagnostic tests were performed with the nonparametric U-statistic method.

Results

BMI-adjusted PSA equaled to unadjusted PSA multiplying 1.09, 1.20, 1.50, and 1.71 for men in overweight, OBI, OBII, and OBIII categories, respectively. The AUC for BMI-adjusted PSA values (0.84) did not differ from PSA; that of the PCPT calculator with BMI-adjusted PSA (0.87) did not differ from the calculator with PSA. Of 2816 men with a PSA less than or equal to 2.5 ng/mL who did not undergo biopsy, 126 (4.5%) would have a BMI-adjusted PSA exceeding 2.5 ng/mL.

Conclusions

Because of lower levels of PSA, overweight and obese men may have diminished cancer detection opportunities when undergoing PSA-based screening.

Section snippets

Material and Methods

The San Antonio Center of Biomarkers of Risk for Prostate Cancer (SABOR) is a National Cancer Institute, Early Detection Research Network–sponsored Clinical Validation Center. SABOR has enrolled community-dwelling men in a biomarker validation cohort since 2000. From this cohort, we identified 3697 men (3432 noncancers and 265 cancers) who were enrolled between November 2000 to May 2009 for this analysis. In these subjects, age, PSA, BMI, DRE, race, first-degree family history of PCa, and

Results

Characteristics of participants are summarized in Table 1. There was no significant difference between cancers and noncancers with regard to mean BMI (P = .20) but some evidence of a shift in the distribution across categories of BMI (P = .06 in Table 1 and P = .03 after combining the OBII and OBIII categories). Among cancers, BMI category did not correlate with high-grade (Gleason score ≥7) PCa (P = .75 and P = .74 for before and after the OBII/OBIII combination, respectively). The area under

Comment

Associations between increased BMI and decreased PSA have previously been reported by many researchers.3, 4, 5, 6, 7, 8, 9, 10 Two explanations have been advanced to explain the lower levels of PSA among obese men: a hemodilution effect as a result of greater blood volume or suppression of PSA production caused by lower testosterone levels and higher estrogen levels among obese men.12, 13, 14, 15, 16 Beyond PCa detection, outcomes after treatment for PCa have been found by several investigators

Conclusions

We observed that increased BMI is not a risk factor for PCa among our SABOR participants. Adjustment for diminished levels of PSA in the general population does not increase the accuracy of PSA-based risk assessment. However, because of lower levels of PSA, overweight and obese men may suffer diminished cancer detection opportunities when undergoing PSA screening and a BMI-based PSA adjustment may be considered.

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    Financial support provided by the Early Detection Research Network, National Cancer Institute, National Institutes of Health, Grant (U01-CA86402) and the San Antonio Cancer Institute (P30-CA54174).

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