HPV test beats Pap for cervical cancer screening
Marilynn Marchione | 5/25/2011, 1:19 a.m.
Two big studies suggest possible new ways to screen healthy people for cervical or prostate cancers, but a third disappointed those hoping for a way to detect early signs of deadly ovarian tumors.
• For women 30 and over, a test for the virus, HPV, is better than a Pap smear for predicting cervical cancer risk, and those who test negative on both can safely wait three years to be screened again.
• 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 notoriously unreliable, but using it this way separates men who need a close watch from those who are so low-risk that they can skip testing for five years or more.
• Screening women with no symptoms for ovarian cancer with a blood test and an ultrasound exam is harmful. It didn’t prevent deaths and led to thousands of false alarms, unneeded surgeries and serious complications.
The last study is a warning to people who get screening tests that aren’t recommended, or who question whether screening can ever hurt.
“The answer is, it could hurt a lot,” said Dr. Allen Lichter, chief executive of the American Society of Clinical Oncology. The group published these and 4,000 other studies last week, ahead of its annual meeting next month.
Cervical cancer is easy to prevent. It’s very slow-growing and screening finds precancerous cells and allows early treatment. The new study was the first big one to examine a newer screening tool, HPV tests, with or without Pap smears in routine practice.
For a Pap test, cells scraped from the cervix, the gateway to the uterus, are checked under a microscope. But this can miss problems or raise false alarms.
HPV tests detect the human papillomavirus, which causes most cases of cervical cancer. But HPV is “the common cold” of the nether regions — most sexually active young people have been exposed to it, said Debbie Saslow, the American Cancer Society’s director of breast and gynecologic cancer. Most infections go away on their own; they’re only a cancer risk when they last a year or more.
Younger women tend to have short-term infections, so Pap tests are a better way to screen them. HPV tests are approved as an option along with Paps for women 30 and older, and the cancer society says that if a woman tests negative on both, she can wait three years to be screened again. Few take this advice, though.
“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.
The new study gives “very, very solid support” for screening less often, Lichter said.
Hormuzd Katki of the National Cancer Institute studied more than 330,000 women getting HPV and Pap tests through Kaiser Permanente Northern California for five years.
Only about three out of 100,000 women each year developed cervical cancer after negative HPV and Pap tests. HPV tests were twice as good as Paps for predicting risk. Adding a Pap after a negative HPV test did little to improve risk prediction.