Résultats d'une étude rétrospective incluant 11.660 hommes ayant subi une prostatectomie radicale pour adénocarcinome de la prostate.

        C'est l'hémodilution due à l'augmentation du volume plasmatique qui est responsable des niveaux bas de PSA observés chez les hommes obèses ayant un cancer de la prostate.

En revanche la quantité de PSA ne diminue pas avec l’augmentation de l'IMC.

JAMA. 2007;298(19):2275-2280.

Context  Recent studies have suggested that obese men have lower serum prostate-specific antigen (PSA) concentrations than nonobese men. Because men with higher body mass index (BMI) have greater circulating plasma volumes, lower PSA concentrations among obese men may be due to hemodilution.

Objective  To determine the association between hemodilution and PSA concentration in obese men with prostate cancer.

Design, Setting, and Participants  Retrospective study of men who underwent radical prostatectomy for prostate adenocarcinoma from 1988 to 2006, using data from the databases of the Shared Equal Access Regional Cancer Hospital (n = 1373), Duke Prostate Center (n = 1974), and Johns Hopkins Hospital (n = 10 287). Multivariate linear regression models adjusting for clinicopathological characteristics were used to analyze the main outcome measures.

Main Outcome Measures  Associations between BMI and mean adjusted PSA concentrations, mean plasma volume, and mean adjusted PSA mass (total circulating PSA protein, calculated as PSA concentration multiplied by plasma volume), assessed by determining P values for trend.

Results  After controlling for clinicopathological characteristics, higher BMI was significantly associated with higher plasma volume (P < .001 for trend) and lower PSA concentrations (P  .02 for trend) in all cohorts. In 2 of the 3 cohorts, PSA mass did not change significantly with increasing BMI. In the third cohort, higher BMI was associated with increased PSA mass (P < .001 for trend), but only between BMI category less than 25 and the other categories.

Conclusions  In men undergoing radical prostatectomy, higher BMI was associated with higher plasma volume; hemodilution may therefore be responsible for the lower serum PSA concentrations among obese men with prostate cancer. Prospective studies are needed to evaluate this association in screened populations.