Analyses of baseline characteristics identified significant associations between BMI and clinical stage, biopsy Gleason score, and pathologic Gleason score. Rates of cT1 disease, higher biopsy and pathologic Gleason scores (7 and 8-10), and positive margins were all highest among men in the obese BMI categories. Mean PSA decreased with increasing BMI, but the association was not statistically significant.
“These findings point to the difficulty of performing a digital rectal exam and of performing surgery in men who are obese. In addition, it is possible that prostate cancer is being detected at a later stage in obese men, perhaps because they have a larger blood volume that results in hemodilution of circulating PSA,” said Dr. Sharma.
“We do not believe that the higher positive margin rate in the obese cohorts explains their increased odds of metastasis and prostate cancer mortality because we adjusted for positive margins in our multivariate model. We are exploring the hypothesis that the associations may be driven by some biological effect.”
The potential implication of obesity for men considering active surveillance was investigated by analyzing Gleason score upgrading and positive margin rates in a subset of 8,487 men who would have qualified for active surveillance based on having a biopsy Gleason score of 6, PSA <10 ng/mL, and cT1 or cT2 disease. Univariate analyses showed both Gleason score upgrading and positive margin rates increased across increasing BMI categories. In multivariable logistic regression analysis, the odds of Gleason score upgrading and having positive margins were 1.4- and 1.7-fold higher among men with BMI 30-34.9 kg/m2 compared with men whose BMI was <25 kg/m2. The odds for those two endpoints were increased 1.6- and 1.9-fold in the BMI ≥35 kg/m2 subgroup compared with the reference cohort.
Dr. Sharma noted that another retrospective study is being planned to investigate if weight loss can abrogate the adverse effect of obesity on prostate cancer recurrence. The study will compare outcomes for obese prostate cancer patients who have undergone bariatric surgery to those who have not.
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