DNA Test Beats Pap Smear in Cervical Cancer Detection, Study Finds

Miranda Curlutu remembers the first time she went to the doctor's office for a Pap smear.

"The first time I went, I cried," says Curlutu. "I was so nervous, and the doctor wasn't very comforting about the situation. I actually brought my mom, but … I still cried."

Cervical cancer screening through Pap smears conducted for years during annual pelvic exams have been the standard screening approach for detecting early phases of the disease.

For some women, however, the annual exam may one day become a thing of the past. DNA tests for the cancer-causing human papillomavirus, which are more likely to detect early forms of cancer, could eventually mean less-frequent visits to the doctor for pelvic exams.

But there's a catch. Since these tests are so sensitive, a small number of women may end up getting false positive results, leading to extra tests and unnecessary alarm.

Studies on these new tests were published Wednesday in the New England Journal of Medicine.

The studies -- one Canadian and one Swedish -- found that HPV testing had almost twice the sensitivity of traditional testing, picking up more precancerous lesions than Pap smears do.

And since these tests are so sensitive, the authors speculated that women with negative tests may be able to safely go longer between pelvic exams for cervical cancer screening.

Sensitive Tests Pick Up More Early Cancer

The DNA-based tests for HPV are performed with a pelvic exam, similar to the kind associated with traditional Pap smears.

But instead of the traditional approach of looking for cells showing early signs of cancer, the samples are sent for DNA tests that look for the presence of the human papillomavirus, a sexually transmitted virus that is the cause of most cervical cancers.

In the Canadian study, researchers assigned more than 10,000 women between 30 and 69 years of age to receive either DNA testing for HPV or traditional pap smears. HPV testing was found to be superior for picking up high-grade precancerous lesions, detecting 95 percent of these precursors to cancer, compared with 55 percent for traditional Pap smears.

"When you do screening, what you really want is a very sensitive test -- you don't want to miss any of your cases," explained the lead author of the Canadian study, Dr. Marie-Hélène Mayrand, associate professor of obstetrics and gynecology at the University of Montreal.

"The problem with Pap testing -- on average, it misses about half of the cases of cervical cancers," she said. "In our study, the sensitivity of Pap was 55 percent, but HPV testing had sensitivity of 95 percent; essentially, it almost didn't miss any high-grade lesions."

And in the Swedish study, scientists assigned 12,527 women between 32 and 38 years old to either receive routine care with Pap smears or routine care plus HPV testing. Fifty-one percent more cancers and high-grade precancerous lesions were found in women who initially received HPV testing in addition to pap smears, leading to earlier treatment.

In subsequent screening examinations, this group was later found to have 42 percent fewer cancers or high-grade precancerous lesions.

"The basic result we found is that if you also have a papillomavirus test [in addition to traditional pap smears], you will have a protection against severe lesions the next time you are screened," said lead study author Dr. Joakim Dillner, professor of virology at Lund University in Sweden. "Your risk will be reduced by half the next time."

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