Prostate Cancer Test Can Be Falsely Interpreted in Obese Men

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Knoxville (WVLT) - Prostate cancer is the second leading cause of cancer deaths in men, behind only lung cancer. Early detection and treatment are the means to beating most forms of the disease, but as medical reporter Jessa Goddard tells us, one of the telltale tests to detect it can be falsely interpreted.

PSA or Prostate Specific Antigen is the gold standard for detecting prostate cancer, but according to a new study, just released today by Duke Prostate Center researchers, PSA scores in obese men are causing their cancer to be missed.

One in three Americans is obese, and it's not just the very large people you think of who fall into this category. A man who is 5'11" and weighs 215 pounds is considered obese, making the findings of the Duke University study important because of the sheer number of people they affect.

"It's an interesting study, and I can see where they're coming from, but I think we have to be a little bit cautious, we don't want to go out and biopsy everybody who walks in the office," Urologist Dr. Fred Kline said.

According to the study, doctors may be missing cancers in obese men because the telltale blood marker, PSA, used to detect the disease can be falsely interpreted as low.
Because obese men have more blood circulating throughout their bodies than normal weight men, the concentration of PSA in their blood can become diluted.

UT Medical Center Urologist Fred Kline says the findings are also significant because digital rectal exams -- usually performed in conjunction with PSA tests are also less accurate in obese men.

"But the other thing you have to consider, for patients who are extremely overweight, it's not that easy to feel their prostate, so PSA values become a little more important," Dr. Kline said.

Doctors have known for some time that obese men tend to have lower PSA scores than normal weight men, but this study proposes a reason as to why, and points to the need for an adjustment in the way doctors interpret PSA scores that will take body weight into account.

"If someone who is in what we call the PSA reflex range, which is approximately 2.5 - 10 nannograms per milliliter, we do something that is called a PSA-2," Dr. Kline said.

An adjustment in the way doctors interpret PSA scores could make the difference in detecting or missing thousands of prostate cancer cases every year.

Previous studies have linked obesity to more aggressive prostate cancers. The finding that prostate cancer may also be more difficult to detect in obese men presents a dangerous one-two punch for men who are already overweight or obese and shows another serious consequence of this country's growing obesity epidemic.