BODY MASS INDEX AS ADVERSE PATHOLOGY PREDICTOR AFTER PROSTATECTOMY 497

racy or operating characteristics of the PSA test.The sensitivity/specificity combination for a partic-ular PSA value or range of values does not have to beidentical across BMI categories to yield a similarAUC and different-shaped curves can have similarAUCs. Thus, there is no paradox in finding thatobese men have lower PSA and PSA has similaroperating characteristics in obese and nonobese

REFERENCES

REPLY BY AUTHORS

serum markers, including carcinoembryonic antigen

be vigilant when treating obese patients and makeappropriate adjustments to evaluate PSA despitethe similarity in operating characteristics acrossBMI groups.

Daniel A. Barocas

Department of Urologic SurgeryVanderbilt University Medical Center

men. As these authors contend, we must continue to Nashville, Tennessee

These authors performed a large, multicenter, ret-rospective multivariate analysis in 3 cohorts of menwho underwent RP to assess the impact of obesity onthe prognosticating value of preoperative PSA. Theapparent effect of hemodilution on PSA in obese mento date was reported to be minimal at best and itsclinical value remains controversial.1 Most reportedlinkage is based on observational studies, which tra-ditionally perform poorly to establish a cause-and-effect relationship. This study shows no significantimpact of BMI on PSA predictability of high gradecancer recurrence or occurrence and time to bio-chemical failure. Although obesity is associated with

postulate that changes in PSA in the postoperativeperiod in obese men should be blamed. The currentstudy result appears to refute this claim. Likewise arecent large study from The Netherlands showingthat BMI has no prognostic value on biochemicalfailure after RP3 may indicate that PSA changes dueto possible hemodilution (if such exists) are too smallto make any difference in daily clinical practice.

Al B. Barqawi

Division of UrologyDenver School of Medicine

University of Colorado

a higher CaP recurrence rate,2 some investigators Aurora, Colorado

1. Rundle A, Richards C and Neugut AI: Body com-position, abdominal fat distribution, and prostate-specific antigen test results. Cancer Epidemiol Bio-

2. Freedland SJ, Wen J, Wuerstle M et al: Obesity isa significant risk factor for prostate cancer at thetime of biopsy. Urology 2008; 72: 1102.

vide prognostic inf

3. van Roermund JG, Kok DE, Wildhagen MF et al:Body mass index as a prognostic marker for bio-chemical recurrence in Dutch men treated withradical prostatectomy. BJU Int, Epub ahead of print

markers Prev 2009; 18: 331.February 11, 2009.

These study results, which show no significant differ-ence in AUC (prediction ability of preoperative PSA todetermine adverse pathological features and biologicalrecurrence) across BMI categories mean that urolo-gists can detect and treat CaP as well in obese patientsas in normal weight patients despite lower PSA. Thedilution hypothesis may be an explanation of the re-sults but there may be other possible explanations.Another explanation may be that physicians rely notonly on PSA, but also on other signs or symptoms, such

These authors also mention that patients withhigher BMI were younger and as a result more likelyto have been treated in recent years. These resultsmay indicate bias if RP techniques advanced duringthe study period of 1988 to 2007.

BeLong Cho

Health Promotion CenterDepartment of Family Medicine

Seoul National University Hospital

as rectal examination results and urinary symptoms. Seoul, Korea

Evidence for obesity related hemodilution of PSAcontinues to emerge in the scientific literature. Arecent report on a cohort of 28,380 men from theprostate arm of the Prostate Lung Colon and Ovarystudy indicated that increased plasma volumes inobese men could lower PSA concentrations.1 More-over, 2 additional studies on hemodilution of other

and carbohydrate antigen 19-9 in men undergoingannual physical examination2 and alkaline phos-phatase in men with castrate resistant prostate can-cer,3 further support the hypothesis that lower se-rum marker levels in men with increased BMI aredue to larger plasma volume.

In our study the predictive ability of PSA to pro-

ormation in men treated similarly