Predicting absolute risk of CIN3 during post-colposcopic follow-up: results from the ASCUS-LSIL Triage Study (ALTS).

OBJECTIVE: At present, clinical management of women referred to colposcopy but found to have <CIN2 remains unclear. Using data from the ASCUS-LSIL Triage Study (ALTS) to inform clinical management, we calculated the absolute risk for developing CIN3 within 2 years of referral to an enrollment colposcopy. STUDY
DESIGN: Women included in the analyses: (1) were initially referred to ALTS with a community cytologic interpretation of atypical squamous cell of undetermined significance (ASCUS) or low-grade squamous intraepithelial lesions (LSIL); (2) had a colposcopic evaluation and biopsy, if indicated, resulting in a diagnosis <CIN2; and, therefore (3) were followed without treatment. Results from subsequent human papillomavirus (HPV) testing, liquid-based cytology interpretations, and a second colposcopic evaluation at least 6 months after and within 2 years of the first colposcopic evaluation were used to calculate absolute risks for CIN3.
RESULTS: Women with HPV-negative test results were at low risk for CIN3 regardless of other test results. Among HPV-positive women, increasing absolute risks of CIN3 were observed with increasing cytology severity: 7% (normal), 11% (ASCUS and LSIL), and 45% (HSIL). The highest absolute risk for CIN3 (67%) was observed for HPV-positive women with HSIL and a colposcopic impression of high-grade/cancer on the second colposcopy.
CONCLUSION: In the ALTS population, after the first colposcopic diagnosis of <CIN2, clear risk stratification for CIN3 outcomes was obtained among women with a subsequent HPV-positive test. Because absolute risk for histologic CIN3 outcomes was high for women with HPV positive tests, HSIL cytology, and a high-grade impression at second colposcopy, it is worth considering whether this combination of findings might warrant immediate excisional therapy in some circumstances.