Background: In Canada Cervical cytology (Pap) has been the foundation of CxCa screening for over half a century. Primary HPV DNA testing is now replacing it in some provinces whereas in the United States, Pap and HPV testing is used together (co-testing). The Cervix-HPV Cancer Risk Management Model (CRMM) is a Canadian population HPV transmission micro-simulation model that projects impacts of CxCa screening strategies.
Objectives: To assess the health and economic outcomes of 7 CxCa screening strategies in Canada using the Cervix-HPV CRMM.
Methods: We compared 3 types of screening strategies: 1) Pap only: triennial Pap in ages 21-65 (PAP3); 2) Pap/HPV: triennial Pap in ages 21-29 and HPV DNA every 3 (PAP3/HPV3) or 5 (PAP3/HPV5) years from ages 30-65; and 3) Co-testing: triennial Pap in ages 21-29 and co-testing every 5 years from ages 30-65 with 3 distinct abnormal result follow-up algorithms, (CoT1/2/3), and co-testing every 5 years from ages 21 to 65 (CoT4). We assumed 70% HPV vaccination rate of girls aged 12 starting in 2008 and 80% recruitment rate of age-eligible women, with 70% rescreening. Health system costs and quality-adjusted life-years (QALYs) were discounted at 3%. Costs were in 2008 Canadian dollars.
Results: Compared to PAP3, the PAP3/HPV3 strategy would show the most decline in incidence15.8%, followed by the 3 strategies CoT/1/2/3 (11%), CoT4 (10%), and PAP3/HPV5 (8%). Similarly, PAP3/HPV3 would show the most decline in deaths (16%), followed by CoT1/2/3/4 (11%) and PAP3/HPV5 (9%). CoT strategies required the most colposcopies in 2050, with between 50% (CoT4) and 88% (CoT1) more than for PAP3, 14% more for PAP3/HPV3 and 10% less for PAP3/HPV5 scenarios. Lifetime costs of vaccination, screening and treatment would be the least with PAP3/HPV5, 5.4% less compared to PAP3. Pap3/HPV3 and CoT1/2/3/4 would be more costly from 17.4%, and 33 to 40% more, respectively. All strategies would have gains in QALYs. Given incremental cost-effectiveness ratios, PAP3/HPV5 would dominate PAP3. Pap3/HPV3 would dominate all CoT strategies, and compared to PAP3/HPV5, would cost $141,000 per QALY gained.
Conclusions: The Cervix-HPV CRMM projects that in a setting of HPV vaccination, triennial primary HPV DNA testing replacing triennial Pap at age 30 would be more effective than triennial Pap, and more effective and less costly than the co-testing strategies. While extending the screening interval from 3 to 5 years and using HPV DNA testing would be less costly than triennial Pap, it would be less costly and less effective than HPV DNA testing every 3 years. Triennial HPV testing would cost $141,000 per QALY gained compared to HPV testing every 5 years