Association Of Body Mass Index With Prostate Cancer Biochemical Failure

Main Category: Prostate / Prostate Cancer
Also Included In: Urology / Nephrology
Article Date: 24 Jul 2010 - 16:00 PDT

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UroToday.com - Our study of prostate cancer patients' outcomes relative to their body mass index (BMI) is interesting because of the lack of effect we observed between BMI and the study's endpoint: biochemical failure. Our study group was comprised of low- and intermediate-risk patients in order to minimize the potential for disease virulence to overwhelm or negate the effect of BMI on the endpoint. We also tried to account for the frequency of post-therapy PSA testing, one of the major problems with measuring biochemical failure.

We did observe that the "usual" predictors of biochemical failure (pre-treatment PSA and biopsy Gleason score) were found to significantly affect the endpoint. Whether one treated BMI as a continuous variable or as a categorical variable, it was a poor predictor of biochemical failure. Two secondary findings are worth mentioning. The first is that African American patients were at a slightly higher risk to experience a biochemical failure. The second is that patients with a high BMI treated with radical prostatectomy fared worse than those with a lower BMI.

Reasons for the lack of correlation between BMI and biochemical failure are not clear. It may be due to the fact that our study population is very homogeneous relative to BMI, and without variability, it is very difficult to show a correlation with an endpoint. The endpoint itself, biochemical failure, may be a bad surrogate for disease recurrence despite our efforts to account for the PSA testing frequency. Also, there is the potential for measurement error since patient heights were generally not directly measured and weights were measured with different scales across our institution. Alternatively, it is plausible that BMI has no effect on disease outcomes after treatment.

Many other investigators have noted worse outcomes for African American patients. One of the arguments for this observation is that African Americans are more poorly screened for prostate cancer and therefore are more likely to present with more advanced disease. This is not a tenable explanation here because all of the patients in our study had low or intermediate-risk disease. The explanation that seems most applicable is that African Americans are known to have a higher average testosterone level than other racial or ethnic groups and this may translate into prostate cancer that has a more aggressive behavior, regardless of pre-treatment PSA or Gleason score.

The finding that patients with a high BMI do worse after radical prostatectomy relative to those with a lower BMI is probably a technical issue. Patients with a large BMI present greater difficulty with access to the prostate, thereby potentially limiting the extent and/or quality of resection.

Though the role of BMI and the risk of being diagnosed with prostate cancer and the severity of prostate cancer are unclear, BMI does not appear to impact a patient's outcome after treatment for prostate cancer. A patient with a large BMI who has been diagnosed with low or intermediate-risk disease does not need to be treated more aggressively than normal weight patients. A large BMI may be an important factor to consider however when offering such a patient a radical prostatectomy.

Written by Jay P. Ciezki, MD as part of Beyond the Abstract on UroToday.com. This initiative offers a method of publishing for the professional urology community. Authors are given an opportunity to expand on the circumstances, limitations, etc., of their research by referencing the published abstract.

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