CLINICAL EFFECTIVENESS AND COST-EFFECTIVENESS OF QUADRIVALENT HUMAN PAPILLOMAVIRUS VACCINATION IN HIV-NEGATIVE MEN WHO HAVE SEX WITH MEN TO PREVENT RECURRENT HIGH-GRADE ANAL INTRAEPITHELIAL NEOPLASIA

Purpose: Recent evidences show that high-risk populations like HIV-negative men who have sex with men (MSM) benefit if vaccinated with quadrivalent human papillomavirus (HPV) vaccine (qHPV) on the onset of receipt of treatment for high-grade intraepithelial neoplasia (HGAIN), a precursor to anal cancer. This is because the vaccine may lower the risk of recurrent or persistent HGAIN. We examined the long-term clinical and economic benefits of qHPV as a secondary/adjuvant prevention strategy in the prevention of recurrent HGAIN, in HIV-negative MSM, 27 years or older.

Method: A cost-effectiveness analysis was conducted from a health care perspective. We constructed a Markov model to evaluate the clinical effectiveness and cost-effectiveness of: (1) no qHPV after treatment for HGAIN versus (2) qHPV after treatment for HGAIN. Model parameters, including natural history of anal cancer, vaccine efficacy measured in terms of hazard ratio (HR) (reduction in the chance of developing recurrent HGAIN), HGAIN treatment efficacy, utilities, and costs, were obtained from the literature. The outcomes were measured in terms of lifetime risk of anal cancer, lifetime cost, quality-adjusted life years (QALYs), and incremental cost-effectiveness ratios (ICERs). Sensitivity analysis was conducted on all model parameters measured at three scenarios — base case vaccine efficacy (HR = range from 0.41 to 0.52), high vaccine efficacy (HR=0.25), and low vaccine efficacy (HR=0.75).

Result: Vaccinating HIV-negative MSM reduced the lifetime risk of anal cancer by 60.77% at an ICER of US$87,240 (95% CI: $22,301-$144,187) per QALY. The results were highly sensitive to vaccine efficacy, transition of HGAIN to anal cancer, cost of treatment for HGAIN, and the vaccine duration of protection, and less sensitive to HPV clearance, cost of qHPV, and the transitions from normal to low-grade anal intraepithelial neoplasia (LGAIN) and normal to HGAIN. With an HR of 0.3, the ICER was well below the $50,000 willingness to pay (WTP); with an HR of 0.5, the ICER was still below the WTP of $100,000. The most critical disease-related factor influencing the cost-effectiveness was the progression of HGAIN to anal cancer. At the annual transition probability lower than 0.001, the vaccine was almost always cost-effective (i.e., the ICER was below $50,000).

Conclusion: Vaccinating HIV-negative MSM treated for HGAIN decreases the lifetime risk of anal cancer and is likely to be a cost-effective intervention.