Analysis: Obesity-prostate cancer link?
By Laura Gilcrest
May 25, 2006, 19:00 GMT
ATLANTA, GA, United States (UPI) -- Although researchers have not yet definitively linked obesity to a higher risk of prostate cancer, new studies have uncovered some intriguing new clues regarding a possible connection, including that obesity might indeed be predictive of the disease and that clinically obese men might have more aggressive forms of prostate cancer.
The new data also suggest that the obesity factor tends to cloud doctors` ability to diagnose prostate cancer using standard prostate-specific antigen testing.
Health experts already warn that obese patients have a 50-percent higher mortality risk from cancer generally. But while recent studies have established connections between obesity and other diseases like breast and colon cancer, the obesity-prostate cancer link remains \'controversial,\' said researchers at this week`s annual meeting of the American Urological Association in Atlanta.
However, a recent study of 587 men diagnosed with prostate cancer between 2003 and 2005 showed a relationship between patients with a body mass index of more than 30 and a higher PSA \'velocity,\' or the rate of speed with which a patient`s PSA reading climbs higher.
For example, if a patient`s PSA test score jumps from 1 to 3 in a relatively short time, that shows the patient has an aggressive form of the disease, said study author Stacy Loeb of Georgetown University Hospital in Washington.
And the more aggressive the disease, the worse the outcome for the patient after surgery, meaning the patient is more likely to die in spite of surgery to treat the disease.
\'Our data suggest that obese men are more likely to die following treatment,\' Loeb told United Press International, raising the possibility that obese patients are more likely to have aggressive, advanced disease.
Another study released at an AUA news briefing showed that obesity appears to skew PSA test results, making the disease harder to diagnose in clinically obese patients. The study, presented by Robert Grubb, with the St. Louis-based Washington University School of Medicine, focused on 38,349 mostly Caucasian prostate-cancer patients with a median age of 63.
The data pointed to an inverse relationship between BMI and PSA levels, so that the greater the patient`s BMI, the lower his PSA score, which is likely due to the obese patient`s lower testosterone levels, Grubb told UPI.
This makes diagnosing prostate cancer particularly challenging for doctors, since the data also show that obese men who were PSA-tested then sent on for biopsy were 25-percent more likely than their thinner counterparts to have a positive biopsy result, he noted.
The data show a BMI of more than 30 is predictive of prostate cancer, Grubb said.
Based on these findings, doctors should figure in the obese patient`s typically lower PSA results when determining if a biopsy is needed, the researchers said, by adjusting the PSA score upward. So an obese man`s 1.5 or 1.9 PSA score, for example, might be interpreted as a normal-weight patient`s PSA reading of 2, they said.
While these studies seem to draw researchers closer to the elusive obesity connection, a third study presented at the briefing suggested there was no relationship between obesity and the need for secondary treatment, nor a link between obesity and inferior overall survival in prostate-cancer patients.
\'Our data suggest that prostate cancer survival is related to disease characteristics,\' said study author Phillip Ross, a clinical oncology fellow at the University of California at San Francisco.
Obesity was not associated with decreased disease-specific or overall survival, he said. However, Ross noted that the study had its limits; for example, it involved a 36-month follow-up, and prostate cancer is a characteristically slow-moving disease. \'We encourage ongoing studies,\' he told UPI.
Ross added that another study that drew from the same patient database did point to an increased risk of prostate-cancer recurrence in obese patients but cautioned that other factors might also be at play in poorer outcomes for the overweight, including the fact that obese patients pose a tougher challenge in performing surgical procedures.
The study presenters also warned that PSA testing is by no means a \'perfect predictor\' of prostate cancer -- for example, older patients and those with larger prostate glands typically test at higher levels -- but that the test is a good diagnostic marker for the disease.
Despite some disagreement, experts generally agree that a PSA score of between 2.5 and 4 warrants a biopsy, they said.
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