Long term risk prediction of p16/Ki-67 dual stain in triage of HPV-positive women

Background: Human papillomavirus (HPV) testing has been approved as a primary strategy for cervical cancer screening, either alone or in combination with cytology (co-testing), based on its high sensitivity and long-term reassurance against cervical precancer following a negative test result. However, nearly twice as many women will screen positive for HPV compared with cytology-based screening. Thus, effective management of HPV-positive women requires triage markers to distinguish those at high-risk who should be referred to colposcopy from those with benign infections who can safely return to routine screening. p16/Ki-67 dual stain cytology has previously shown good risk stratification for triage of HPV-positive women; however, studies with follow-up extending beyond 3 years are lacking. We evaluated the long-term risk prediction of p16/Ki-67 for detection of cervical precancer (cervical intraepithelial neoplasia grade 3 or worse, CIN3+) in a large population of HPV-positive women. Methods: 1,588 HPV-positive women screened with HPV/cytology co-testing were enrolled in 2012 at Kaiser Permanente Northern California. p16/Ki-67 cytology was performed on residual Surepath material and slides were evaluated for p16/Ki-67 positivity. Cervical histology endpoints were ascertained from the clinical database with follow-up through 2017. We conducted a Kaplan Meier analysis to estimate risk of CIN3+ by p16/Ki-67 and cytology (atypical squamous cells of undetermined significance or worse, ASC-US+, versus normal cytology). Risks were compared to internal benchmarks for colposcopy referral and for a one year return interval. Results: In women testing p16/Ki-67 positive at baseline, the 2-year risk of CIN3+ was 14.3%, compared with 2.2% in p16/Ki-67-negative women. For ASC-US+, the risk was 12.6% and 2.9% for normal cytology. The 5-year risk of CIN3+ in p16/Ki-67-positive women was 21.6% and 5.0% in p16/Ki-67-negatives. The 5-year risk of ASC-US+ was 17.1% compared to 8.2% for normal cytology. Among p16/Ki-67-negatives, the risk remained below the colposcopy referral threshold for 5 years while in women with normal cytology, the colposcopy referral threshold was crossed after year 3. Conclusion: In the first study evaluating long-term risk stratification of p16/Ki-67 dual staining, p16/Ki-67- negativity provided strong reassurance against CIN3+ for at least five years. In contrast, the risk in women with normal cytology crossed the colposcopy referral threshold after three years. These data support use of p16/Ki-67 for triage of HPV-positive women with the possibility of extending surveillance intervals in p16/Ki-67-negative women. Citation Format: Megan A. Clarke, Barbara Fetterman, Mark Schiffman, Philip E. Castle, Eric Stiemerling, Diane Tokugawa, Nancy Poitras, Walter Kinney, Thomas Lorey, Nicolas Wentzensen. Long term risk prediction of p16/Ki-67 dual stain in triage of HPV-positive women [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2202.