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This article is from the WebMD News Archive
Obesity Affects Prostate Cancer Test
Nov. 20, 2007 -- Obese men may have prostate cancer despite relatively low values on a prostate cancer screening test called the PSA test, a new study suggests.
The PSA test detects PSA -- prostate-specific antigen -- in the blood. Only prostate cells give off PSA. PSA levels can rise as prostate tumors grow.
Earlier studies showed that obese men have slightly lower PSA concentrations than lean men do. It's not clear why this is so. New findings from Duke University researcher Stephen J. Freedland, MD, and colleagues now suggest an answer.
"Being a big guy, you have enormous blood volume, so PSA is diluted," Freedland tells WebMD. "Obese men having these lower PSA values due to the dilution factor means we are going to miss some of them early on."
The researchers reviewed medical records from some 14,000 men with prostate cancer who had their prostate glands removed. Based on the men's body mass index, and adjusting for differences in the men's clinical conditions and prostate pathology, the researchers used pre-operative PSA test values to calculate the actual amount of PSA in the men's blood.
They found that obese men had lower PSA values than did non-obese men even though they had equal or even higher amounts of PSA in their blood.
"What this suggests is if we use the same PSA threshold for obese and normal-weight men, we may be missing some cancers," Freedland says. "For example, a PSA score of 4.1 in an obese man would be diluted down to a 3.3."
Alan R. Kristal, DrPH, one of the researchers investigating the link between obesity and prostate cancer, strongly disagrees with Freedland's calculation. Kristal is associate head of the cancer prevention program at Seattle's Fred Hutchinson Cancer Research Center.
"This is an over-interpretation of the data. Most studies show the difference is much smaller," Kristal tells WebMD. "Doctors will look not just at the PSA level but the speed of PSA increase over time, the PSA relative to other men the same age, findings from a digital rectal exam, and other information before they make a decision on whether to do biopsy. These teeny-tiny differences due to obesity have no impact."
It's an important dispute to resolve. As Freedland points out, there soon will be other blood tests for other kinds of cancer.
"This issue is something we need to keep in mind as we move forward with blood-based cancer screening," Freedland says.
Freedland and colleagues report their findings in the Nov. 21 issue of The Journal of the American Medical Association.
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Indication
Uroxatral® (alfuzosin HCl 10 mg extended-release tablets) is an alpha1-blocker for the treatment of the signs and symptoms of BPH.
Important Safety Information
Do not take UROXATRAL if you have liver problems or if you are taking antifungal drugs like ketoconazole or itraconazole, or HIV drugs like ritonavir.
UROXATRAL can cause a sudden drop in blood pressure, especially when starting treatment. This may lead to fainting, dizziness, and lightheadedness. Do not drive, operate machinery, or do any dangerous activity until you know how UROXATRAL will affect you. This is especially important if you already have a problem with low blood pressure or take medicines to treat high blood pressure. There may be an increased risk of low blood pressure and fainting when taking UROXATRAL in combination with blood pressure medication or nitrates, or erectile dysfunction medication.
If considering cataract surgery (clouding of the eyes), tell your eye surgeon that you are currently taking UROXATRAL or have previously been treated with an alpha-blocker.
Before taking UROXATRAL, tell your doctor if you have kidney problems.
Also, tell your doctor if you or any family member(s) have or take medications for a rare heart condition known as congenital prolongation of the QT interval.
BPH and prostate cancer can cause the same symptoms. However, UROXATRAL is not a treatment for prostate cancer.
The most common side effects with UROXATRAL are dizziness, upper respiratory tract infection, headache, and tiredness.
Please see UROXATRAL full prescribing information.
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