Abnormal Cells in Cervix Raise Cancer Risk: Study

Whether abnormal changes in cervical cells -- known as cervical intraepithelial neoplasia (CIN) -- return or develop into cervical cancer depends in part on a woman?s age and the type of treatment she receives, a new study finds.

CIN is mainly caused by human papillomavirus (HPV), a common STD. The condition is grouped into three stages: mild or grade 1, with just a few abnormal cells; grade 2; and severe or grade 3, in which precancerous cells are found in the top layer of the cervix. Pap smears sample the cervix for evidence of CIN.

Joy Melnikow of the University of California-Davis and colleagues studied more than 37,000 women from Canada?s British Columbia Cancer Agency who were treated for CIN from 1986 to 2000. These women were compared to a group of more than 71,000 who had no history of abnormal cervical cells. Both groups were followed through 2004.

According to the researchers, the risk of cervical cancer and recurrence of grade 2 or 3 CIN was highest for women over age 40, those previously treated for grade 3 abnormal cells, and those whose cells were frozen via cryotherapy. Women who underwent cone biopsy, whereby cells are surgically removed, were the least likely to have recurrent CIN.

Melnikow added that in general, most recurrences of CIN happened in the first six years of treatment. Women who have been treated for CIN have "a low, but higher-than-average risk of invasive cancer, so they need regular screening over an extended period of time," she said.

In addition, women treated surgically have a higher risk of bleeding and preterm labor when they become pregnant, said Melnikow. "Younger women planning later pregnancies may prefer cryotherapy; their risk of recurrence is lower and a recurrence can be treated again," she said.

The study could not assess whether women experiencing recurrence had HPV infections that caused their original abnormal cells to return, the researchers noted.

The study, "Cervical Intraepithelial Neoplasia Outcomes After Treatment: Long-Term Follow-Up from the British Columbia Cohort Study," was published online in the Journal of the National Cancer Institute (2009;doi:10.1093/jnci/djp089).

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