Recent studies have suggested that obese men have lower serum prostate specific antigen (PSA) concentrations relative to non-obese men. Researchers from centers across the USA hypothesized that the increased circulating plasma volume in men with higher body mass index (BMI) dilutes curculating PSA resulting in lower serum PSA concentrations on blood tests.

To test this they analyzed the relationship between serum PSA concentration, body mass index (BMI), plasma volume (calculated based upon age and estimated body surface area) and total PSA mass (PSA concentration multiplied by plasma volume) using a linear regression model adjusting for age at surgery, race, year of surgery, clinical stage, SEARCH site, pathological Gleason sum, extracapsular extension, surgical margins, seminal vesicle invasion and prostate specimen weight among 1304 men who underwent radical prostatectomy within the Shared Equal Access Regional Center Hospital (SEARCH) Database between 1991 and 2006.

Results: After controlling for clinical and pathological factors, higher BMI was significantly associated with higher plasma volume (p=0.005, see table) and lower PSA concentrations (p<0.001). There was no significant association between BMI and adjusted PSA mass (p=0.52).

Conclusions: In a cohort of men with prostate cancer, hemodilution due to greater plasma volume explained all of the lower serum PSA concentration observed among obese men. Future studies are needed to confirm these findings and to assess whether this phenomenon of tumor marker dilution occurs among obese people with other cancers as well. If confirmed, these findings may have broad implications for cancer screening in general among obese people.

Article title authorships:

CAN HEMODILUTION EXPLAIN THE LOWER PSA CONCENTRATIONS AMONG OBESE MEN?

Lionel L Baez, MD, Robert J Hamilton, MD, Robin T Vollmer, MD, Judd W Moul, MD, Christopher L Amling, MD, Christopher J Kane, MD, William J Aronson, MD, Matha K Terris, MD, Joseph C Presti, Jr, MD, Stephen J Freedland, MD. Duke University Medical Center, Durham, NC; Durham VAMC, Durham, NC; University of Alabama at Birmingham, Birmingham, AL; VAMC San Francisco, San Francisco, CA; VA Greater Los Angeles Healthcare System, Los Angeles, CA; VAMC Augusta, Augusta, GA; VAMC Palo Alto, Palo Alto, CA