RISK OF CERVICAL CANCER ELEVATED FOR DECADES AFTER CIN

NEW YORK (Reuters Health) May 12 - Previous treatment for cervical intraepithelial neoplasia (CIN) is associated with a substantial risk of recurrence during the first 2 years, and of invasive cancer for at least 18 years, necessitating long-term surveillance, investigators report in the May 20th issue of the Journal of the National Cancer Institute.

"Lack of data on long-term outcomes, including risks of recurrence among women treated for CIN, is a critical barrier to the formulation of evidence-based recommendations for follow-up surveillance strategies," Dr. Joy Melnikow at the University of California, Davis in Sacramento, and colleagues write.

To study this issue, they used records from the British Columbia Cancer Agency cytology database linked to cancer registry and vital statistics data. The CIN cohort included 37,142 women treated for CIN 1, 2, or 3 between 1986 and 2000. A control group included 71,213 women with three consecutive normal cervical cytology tests and no previous history of CIN.

During follow-up through 2004, there were 3013 women in the CIN group diagnosed with subsequent CIN 2/3 and 989 in the control group with a first diagnosis of CIN 2/3.

Rates of CIN 2/3 declined rapidly for the first 2 years after initial treatment, falling below 1% after 6 years, comparable to the rate in the comparison cohort. Overall cumulative rates during those 6 years ranged from 5% for those treated for CIN 1 to 14% for CIN 3.

The rate of invasive cervical cancer was 37 cancers per 100,000 woman-years in the CIN group versus 6 per 100,000 in the control group. The difference between groups continued to increase with time over 18 years of follow-up.

Initial cryotherapy as opposed to excisional procedures was associated with higher risk of subsequent disease (adjusted odds ratio for invasive cancer, 2.98). Risks were also higher for initial CIN 3 versus CIN 1 and 2 (adjusted OR, 4.10), and for age over 40 versus younger age (adjusted OR, 1.75).

Dr. Melnikow's team advises "routine screening after an initial period of more intensive follow-up that may take the form of cytology, HPV testing, or cytology with colposcopy during the first 6-18 months. Given ... the ongoing elevated risk of invasive cervical cancer, it appears that consistency of follow-up for 10-20 years may be important for detecting disease after treatment."