Weight gain over time is linked to decline in prostate-specific antigen (PSA) levels supporting ?obesity-related hemodilution? ? a phenomenon that potentially results in substantial delays in the detection of prostate cancer among obese men, according to a study released today by Lionel Ba?ez, MD, Duke University Medical Center, at the Prostate Cancer Research Program?s (PCRP?s) Innovative Minds in Prostate Cancer Today (IMPaCT) conference in Orlando, Fla.

The U.S. Centers for Disease Control and Prevention (CDC) reported that approximately 32% of men were obese in 2008, and these statistics continue to rise. Studies continue to demonstrate that obesity is strongly associated with higher rates of prostate cancer death.

Detect and diagnose
Since the late 1980?s, PSA blood levels have been commonly used to detect and diagnose early-stage prostate cancer in men. However, new research supports the ?hemodilution? theory that greater plasma volume among obese men is responsible for their lower PSA test results. If proven true, this may result in delayed detection of prostate cancer in men with excess body weight and could explain why obese men with prostate cancer are at higher risk for cancer-death than their non-obese counterparts.

A number of past studies, including Ba?ez?s 2007 report in JAMA, have examined the relationship between increased body mass index (BMI) and significantly lower PSA levels. In this recently completed study, he found new evidence for PSA hemodilution. Specifically, this study illustrated that, in an individual man, weight gain is correlated with corresponding declines in PSA test results. Through this study, Dr. Ba?ez concluded that for every 10 pounds gained in body weight, PSA levels significantly decrease by 2%. These recent findings strongly support hemodilution as the phenomenon responsible for lower PSA concentrations in obese men, making early prostate cancer detection in obese men quite challenging.

Ongoing research
Ba?ez continues to build on his discoveries, focusing future research on examining racial differences in hemodilution and determining whether excess body weight should be adjusted for during prostate cancer screening. As he has stated, ?It is imperative that we continue to ascertain the clinical impact of hemodilution. Further research will help us to determine whether adjusted cut points will provide a favorable solution to optimize early detection of prostate cancer in obese men. These findings could affect long-term survival of thousands of men afflicted with prostate cancer across the country.?

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Fighting prostate cancer
The PCRP, a program within the Congressionally Directed Medical Research Programs (CDMRP), funded the studies. The program is committed to improving early diagnosis and detection, developing new and effective therapies and prognostic tools, and improving the quality of life for all persons affected by prostate cancer.

?Since its inception, the PCRP has been committed to fighting prostate cancer,? said Navy Captain Melissa Kaime, MD, Director of the CDMRP. ?In a population where obesity is prevalent, the results of this study have the potential to transform the diagnosis of prostate cancer among overweight men and save lives.?

For more information:
– Banez LL, Goldberg KC, Hamilton RJ, Freedland SJ. Weight Gain is Associated with Lower Prostate-Specific Antigen (PSA) Concentrations in Men without Prostate Cancer Followed Over Time: Evidence for Obesity-related PSA Hemodilution (Poster session 2 – P21-8, Friday, March 11, 2011; 4:00?7:00 p.m.; Innovative Minds in Prostate Cancer Today)
– Ba?ez LL, Hamilton RJ, Partin AW, Vollmer RT, Sun L, Rodriguez C, et al. Obesity-related plasma hemodilution and PSA concentration among men with prostate cancer. JAMA. 2007 Nov 21;298(19):2275-80
– Wallner LP, Morgenstern H, McGree ME, Jacobson DJ, St. Sauver JL, Jacobsen SJ, Sarma A. The Effects of Body Mass Index on Changes in Prostate Specific Antigen Levels and Prostate Volume: Implications for Prostate Cancer Detection. OnlineFirst January 17, 2011; doi: 10.1158/1055-9965.EPI-10-1006

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