Competing Risks Survival Analysis of Cervical Cancer Progression and Regression among Women in Kenya
Joseph Mungania Mugambi
Department of Mathematics and Statistics, University of Embu, Embu, Kenya.
Maurice Wanyonyi *
Department of Mathematics and Statistics, University of Embu, Embu, Kenya and African Institute for Capacity Development (AICAD), Nairobi, Kenya.
*Author to whom correspondence should be addressed.
Abstract
Background: Cervical cancer is a leading cause of cancer-related death among Kenyan women. The bidirectional natural history of cervical intraepithelial neoplasia (CIN) – both progression and regression – remains poorly understood in low-resource settings. We quantified competing risks of CIN progression and regression and identified their predictors using longitudinal data from a Kenyan referral hospital.
Methods: We conducted a retrospective cohort study of 550 women with histologically confirmed CIN or normal cervix and documented HPV testing at Meru Level 5 Hospital. Progression (to a higher grade lesion or invasive cancer) and regression (to a lower grade lesion or normal epithelium) were competing first events. Cause-specific Cox and Fine-Gray subdistribution hazard models estimated associations with age, HPV status, HIV status, smoking, parity, and screening frequency. Cumulative incidence functions and bootstrap resampling assessed model stability.
Results: HPV positivity was the strongest predictor of progression (cause-specific HR = 7.90, 95% CI 4.71–13.26; subdistribution HR = 7.22, 95% CI 4.27–12.21). Higher parity reduced progression risk (HR = 0.88 per additional birth, 95% CI 0.78–0.98). Five-year progression probabilities increased with baseline CIN stage: 0.09 (CIN1), 0.25 (CIN2), 0.45 (CIN3). The model showed good short-term discrimination (1-year AUC = 0.882). Bootstrap confirmed robustness.
Conclusion: HPV infection and parity are key determinants of CIN progression in this Kenyan cohort. Competing risks modelling provides clinically meaningful estimates of progression and regression that can support risk-based cervical cancer screening and management in resource-limited settings.
Keywords: Cervical intraepithelial neoplasia, competing risks, cumulative incidence, disease progression, disease regression, Fine-Gray model, HPV infection, HIV status, Kenya, risk stratification