September 9, 2008 / 4:16 AM / 11 years ago

New cervical cancer test beats pap smear

LONDON (Reuters) - A new way to test for cervical cancer is more accurate than a pap smear and identified more dangerous lesions, an Italian study showed on Tuesday.

Cervical cancer cells are seen in a handout photo. REUTERS/NCI/Handout

Researchers used the traditional test for the human papilloma virus that causes cervical cancer and combined it with another that indicated specific cancer-causing activity in cells, said Guglielmo Ronco, a cancer epidemiologist at the Centre for Cancer Prevention in Turin, who led the study.

A simple test for a protein called P16INK4A provided a biomarker showing cell changes that indicated a woman likely has pre-cancerous lesions, Ronco and colleagues reported in the journal Lancet Oncology.

“The marker shows there was some sort of disruption by the HPV virus,” Ronco said. “Only a small minority of women who have an HPV infection actually develop cancer. The challenge is to find out who are at higher risk of developing cancer.”

Cervical cancer is the second most common type of cancer in women. Each year an estimated 500,000 women are diagnosed with the disease and about 300,000 die from it, mostly in the developing world.

Merck & Co’s Gardasil and GlaxoSmithKline’s Cervarix are vaccines that protect against some strains of the virus.

More countries are also adopting screening tests, but the problem is pap smears produce too many false positives — meaning women get a test that suggests they have potentially cancerous or pre-cancerous changes when in fact they do not.

An HPV test looks for the virus while in a pap smear doctors scrape cells from the cervix and examine them under a microscope for abnormalities that could indicate precancerous lesions.

“Most HPV infections simply regress without causing disease,” Ronco said in a telephone interview. “They disappear spontaneously, which is the reason there are so many false positives.”

The Italian team collected cervical cell samples from women who had already tested positive for the HPV virus, most of whom had already undergone an expensive colposcopy exam — a close examination of the cervix using a magnifying instrument.

Then they tested for P16INK4A protein in more than 1,100 of these women and found that it helped identified 88 percent of those who had the cancer-causing lesions with far fewer false positives. The protein is more active in cervical-cancer cells.

The refined test also identified 50 percent more of the dangerous lesions than pap smears and required fewer women to be referred for colposcopy, Ronco said.

Editing by Maggie Fox

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