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Being Overweight Can Affect Prostate Cancer Aggressiveness

(This information is an adapted version for Quest readers of a medical journal article written by Stacy Loeb, MD; Xiaoying Yu, MD; Robert B. Nadler, MD; Kimberly A. Roehl; Misop Han, MD; Sheila A. Hawkins, MD; and William J. Catalona, MD)
Weight, especially being overweight, is a sensitive topic on its own. Studying whether or not weight – in this case Body Mass Index * – affects or can predict outcomes after radical prostatectomy could be an uncomfortable topic to discuss with patients.

But since men can’t change weight after the fact, it is important for them to know beforehand that obesity can affect prostate cancer treatment outcomes.

Prostate cancer researchers are spending a good amount of time taking a look at the relationship of Body Mass Index (BMI) to preoperative PSA velocity and to adverse tumor features in men treated with RRP.

Results

The final verdict is not in yet, but present study results increasingly conclude that being overweight, and especially obese, may be related to increased risks of cancer recurrence.

Our findings show that as the weight category increases, the likelihood of negative results increase. The findings for obese men were worse than for overweight men. The findings for overweight men were worse than for normal weight men.

The effects, if any, of losing weight after prostate cancer diagnosis and treatment are not part of our study.

Relationship Between Weight and Outcomes

We studied the relationship between weight and prostate cancer outcomes. Specifically, we examined the relationships among BMI, PSA Velocity and tumor features in 587 patients who underwent RRP by Dr. William J. Catalona for clinically localized prostate cancer. We compared men with a body mass index of less than 25, 25-29.9 and 30 or greater.

Men with a BMI of 30 or greater were significantly more likely to have a biopsy Gleason score of greater than 6 and a significantly higher percent of cancer in the biopsy specimen.

No differences were found among the BMI groups in percent of men with high-grade tumors, positive surgical margins, seminal vesicle invasion, lymph node metastases or prostate volume larger than 50 cc.

However, obese men had a significantly greater proportion of extracapsular tumor extension and there were a significantly smaller proportion with a tumor volume less than 1 cc.

In addition, we observed a significant association between increasing BMI and preoperative PSAV greater than 2 ng/ml per year

This study did not look directly at whether or not obese men will be more likely to have a recurrence of prostate cancer after treatment. But it is connected to other indicators – such as PSAV, PSA at diagnosis, and extracapsular tumor extension­ – which are known predictors for cancer recurrence after treatment.

Possible Connections

The reasons for the connection between weight and prostate cancer are still under investigation.

We know that levels of estrogen, sex hormone binding globulin and testosterone are affected by obesity, as are insulin and growth hormone levels.

We also know that some obese men produce less PSA than normal weight men and therefore might have delayed diagnosis of prostate cancer.

Earlier stages of cancer, which would result in PSA values calling for a biopsy in normal weight men, would be at a PSA below biopsy threshold for obese men.

Potentially, by the time they are diagnosed, their cancer is more advanced

We still need to investigate dietary factors that promote prostate cancer as well as genetic factors. For example, it might be possible that a trait for height and weight is somehow connected to a gene associated with prostate cancer aggressiveness.

Also, we know that radical prostatectomy is more challenging among obese men and the operation itself might be a factor.

While clearly more work is needed in this area, current studies suggest that obesity makes for more aggressive prostate cancer.

*Body mass index (BMI) is a measure of body fat based on height and weight that applies to both adult men and women. You can go a page from the website of the National Institutes of Health www.nhibisupport.com/bmi/ and compute your own BMI.

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