Cervical intraepithelial neoplasia risk was higher for those previously treated for disease

Active surveillance may be beneficial for women who underwent treatment for cervical intraepithelial neoplasia.

Risk for cervical intraepithelial neoplasia 2 or 3 was linked to grade, treatment type and age, according to the results of a large, retrospective cohort study. Long-term risk for invasive cancer was also higher in women previously treated for CIN.

Researchers examined data from 37,142 women from the British Columbia Cancer Agency cytology database who were treated for CIN 1, 2 or 3 from January 1986 to December 2000. The researchers compared these women with a group of 71,213 women with normal cytology and no previous diagnosis of CIN. Follow-up continued until December 2004.

In the first six years after treatment, the overall cumulative rate of CIN 2/3 after treatment for CIN 1 was 5.6%; after treatment for CIN 2, 9.3%; and after treatment for CIN 3, 14.0%.

The risk for subsequent CIN 2/3 after treatment was associated with initial grade, treatment type and age, according to the researchers. After six years, CIN 2/3 annual rates were the same or lower than rates in the cohort never treated for CIN.

In women aged older than 40, treated for CIN with cryotherapy, the risk for CIN 2/3 recurrence and cervical cancer was the highest. Over six years, the recurrence rates for CIN 2/3 ranged from 2.3% in the group at the lowest risk to 35% in the group at the highest risk.

The overall incidence of invasive cancer was 37 cancers per 100,000 woman-years (95% CI, 30.6-42.5) in the group of women treated for CIN compared with six cancers per 100,000 woman-years (95% CI, 4.3-7.7) in the group of women not treated.

The adjusted OR for invasive cancer was the highest at 2.98 (95% CI, 2.09-4.60) for cryotherapy when compared with other treatments.

“Given the rapid decline in subsequent diagnoses of CIN 2/3 after the first two years, but the ongoing elevated risk for invasive cervical cancer, it appears that consistency of follow-up for 10 to 20 years may be important for detecting disease after treatment,” the researchers wrote.

More intensive follow-up strategies may be important for women aged 40 and older when treated for CIN 3, especially if they were treated with cryotherapy, according to the researchers.

“Cost-effectiveness studies are needed to define optimal surveillance strategies that may differ by CIN grade, treatment type and age,” the researchers wrote.

"This retrospective long-term follow-up study demonstrated that our screening methods are not as sensitive as we might hope and that high-grade CIN (2/3) and/or cervical carcinoma can elude active surveillance methods," Edward J. Wilkinson, MD, professor in the department of pathology at the University of Florida College of Medicine in Gainesville, Fla., said in an accompanying editorial.

Melnikow J. J Natl Cancer Inst. 2009;101-721-728.