September 9, 2008

New Test More Accurate In Cervical Cancer Screenings

A study by researchers in Italy has found that a new cervical cancer test is more accurate than conventional pap smears at detecting dangerous pre-cancerous lesions.

The new test includes a combination of the traditional test for the human papilloma virus (HPV), which causes most cervical cancers, and another test that indicates the presence of a specific cancer-causing activity in cells, said Guglielmo Ronco, who led the study.

"This simple test for a protein called P16INK4A provided a biomarker showing cell changes that indicated a woman likely has pre-cancerous lesions," Ronco and his team wrote in a published report about the research.

"The marker shows there was some sort of disruption by the HPV virus," said Ronco, a cancer epidemiologist at the Center for Cancer Prevention in Turin.

"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.  An estimated 500,000 women are diagnosed with the disease each year, and about 300,000 die from it. Most deaths occur among women in the developing world. 

GlaxoSmithKline's Cervarix and Merck & Co's Gardasil are vaccines that protect against some strains of HPV.

Although more countries are increasingly using screening tests, pap smears produce too many false positive results, in which a test suggests a woman may have potentially cancerous or pre-cancerous changes when they actually do not.

An HPV test looks for the presence of the human papilloma virus, whereas a pap smear examines cells a doctor scrapes from the cervix for abnormalities that could indicate precancerous lesions.

"Most HPV infections simply regress without causing disease," Ronco said in a telephone interview with Reuters.

"They disappear spontaneously, which is the reason there are so many false positives."

Ronco's team collected cervical cell samples from women who had already tested positive for HPV.  Most of these women had already undergone a costly colposcopy exam, which involves a close examination of the cervix with a magnifying instrument.

The researchers then tested for the presence of the protein P16INK4A, which is more active in cervical-cancer cells, in more than 1,100 of these women.  They found that this new test helped identify 88 percent of women with the cancer-causing lesions.  It also produced fewer false positive results.    

Ronco said the new test also found 50 percent more of the dangerous lesions than did pap smears, and required fewer patients to undergo a colposcopy exam.

The study was reported in the journal Lancet Oncology.


Image Caption: ThinPrep Pap smear with group of normal cervical cells on left and HPV-infected cells on right. The HPV-infected cells show features typical of koilocytes: enlarged (x2 or x3) nuclei and hyperchromasia. (Wikipedia)