Body mass index, surgery, and risk for prostate cancer-specific death


It is well understood that there is an association between obesity and future risk for prostate cancer-specific mortality among cancer-free men. What has not been so clear is the relationship between obesity and long-term outcomes, post-treatment, among men diagnosed early with localized disease.

A new study by Vidal et al., published in Prostate Cancer and Prostatic Diseases (and also discussed online in Renal & Urology News), has used data from the Shared Equal Access Regional Cancer Hospital (SEARCH) database to conduct as retrospective analysis of the available data to examine this question among a cohort of > 4,000 men treated at Veterans Administration hospitals and medical centers here in the US.

Here are the core findings from this study:

  • The study database included 4,268 men who underwent a radical prostatectomy in 1990 or later at a total of 6 VA medical canters.
  • Median follow-up among all men still alive at last follow-up was 6.8 years.
  • During the follow-up period
    • 1,384 men (31.6 percent) had a biochemical recurrence (BCR) of their prostate cancer.
    • 117 men (2.7 percent) developed castration-resistant prostate cancer (CRPC).
    • Prostate cancer-specific mortality was documented in  84 men (2.0 percent).
  • On a crude analysis, compared to men with a normal body mass index (BMI) of < 25 kg/m2, i.e., men with a BMI of ≥ 25 kg/m2, were at
    • No increase in risk for BCR (P = 0.259)
    • No increase in risk for CRPC (P = 0.277)
    • No increase in risk for PCSM (P = 0.112)
  • When BMI was categorized, then, compared to men with a normal BMI of < 25 kg/m2
    • Overweight men with a BMI of 25 to 29.9 kg/m2 were at
      • No increase in risk for BCR (P ≤ 0.189)
      • No increase in risk for CRPC (P ≤ 0.189)
      • Significantly increased risk for PCSM (hazard ratio [HR] = 1.99, P = 0.034)
    • Obese men with a BMI of ≥ 30 kg/m2 were at
      • No increase in risk for BCR (P ≤ 0.189)
      • No increase in risk for CRPC (P ≤ 0.189)
      • Significantly increased risk for PCSM (HR = 1.97, P = 0.048)
  • On multivariable analysis adjusting for both clinical and pathological features, again compared to men with a normal BMI of < 25 kg/m2
    • Overweight men with a BMI of 25 to 29.9 kg/m2 were at
      • No increase in risk for BCR (P ≤ 0.114)
      • No increase in risk for CRPC (P ≤ 0.114)
      • Non-statistically significant increased risk for PCSM (hazard ratio [HR] = 1.88, P = 0.061)
    • Obese men with a BMI of ≥ 30 kg/m2 were at
      • No increase in risk for BCR (P ≤ 0.114)
      • No increase in risk for CRPC (P ≤ 0.114)
      • Significantly increased risk for PCSM (HR = 2.05, P = 0.039)

Vidal et al. conclude that men who were either overweight or obese at the time of treatment of localized prostate cancer were at “increased risk of PCSM after radical prostatectomy.”

In the full text of their paper, which is available on line, the authors also discuss, in some detail, why this may be the case (see the Discussion section of this paper). They offer a number of possible reasons, but they come to no specific conclusions about this.

2 Responses

  1. it’s very interesting that the study shows an increase in risk for PCSM but not for BCR or CRPC, since both BCR and CRPC are, of course, precursors for PCSM. Usually with prostate cancer studies it is the reverse, where an effect is found for BCR and/or CRPC but not for PCSM. Any thoughts on the possible meaning or interpretation of this unusual finding?

  2. Nope. No clue. I thought it was unusual too … but I am just the messenger! :O)

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