May 19, 2011

HPV Test More Effective For Predicting Cancer Risk

Researchers have found that a test for HPV is better than a pap smear for predicting cervical cancer risk for women over 30, while a single PSA for men in their mid 40s might predict risk of developing advanced prostate cancer 30 years later.

The two studies found new ways to screen healthy people for cervical or prostate cancers. 

Researchers found that screening women with no symptoms for ovarian cancer with a blood test and an ultrasound exam is harmful.  It did not prevent deaths and led to thousands of false alarms.

The researchers say that the results are a warning to people who get screening test that are not recommend, or who question whether screening can ever hurt.

"The answer is, it could hurt a lot," Dr. Allen Lichter, chief executive of the American Society of Clinical Oncology, said in a statement.

The new study was the first big one to determine if an HPV test is an effective way to screen over Pap smears.

During Pap smears, cells are scrapped from the cervix and are checked under a microscope.  This test has been known to raise false alarms.

HPV tests detect the human papilloma virus, which causes most cases of cervical cancer.

Debbie Saslow, the American Cancer Society's director of breast and gynecologic cancer, said HPV is "the common cold" of the nether regions.  She said most infections go away on their own and they are only a cancer risk when they last a year or more.

"Women still want their annual Pap and doctors still want to give them," and think it's rationing care to test less often, Saslow said.

Lichter said the new study gives "very, very solid support" for screening less often.

Hormuzd Katki of the National Cancer Institute studied over 330,000 women getting HPV and Pap tests through Kaiser Permanente Northern California during the past five years.

About three out of 100,000 women each year developed cervical cancer after negative HPV and Pap test.  HPV tests were twice as good as Paps for predicting risk.

The study did not look at the downside of HPV testing.  HPV tests cost between $80 and $100, compared to $20 to $40 for Paps.

They found that a single PSA blood test at ages 44 to 50 might help predict a man's risk of developing advanced prostate cancer or dying of it up to 30 years later. 

The PSA test is known to be unreliable, but using it this way could help separate men who need a close watch from those who are so low-risk that they can skip testing for five years or more.

Most groups do not recommend PSA tests, but most men over 50 get them anyways.

The new study "is not going to end the controversy, but it suggests a very interesting middle ground," Lichter said in a statement.

Researchers used 12,000 blood samples from Swedish men between the ages 44 to 50 years old. 

The team found that 27 years later, 44 percent of cancer deaths occurred in men whose initial PSAs had been in the top 10 percent when they were 44 to 50 years old.

The cancer society says men should be informed of the risks and benefits of PSA tests starting at age 50, and sooner or blacks and those with a family history of prostate cancer.

The National Cancer Institute, the Swedish Cancer Society and several foundations paid for the PSA study.  The ovarian cancer study involved about 80,00 women and was largely funded by the government.


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