A Model Approach for Assessing the Benefits of HPV Testing against Cytology in Screening for Cervical Cancer Precursors in Thailand

OBJECTIVE: The aim of this study was to compare the efficacy of HPV 16/18 genotyping test, high risk HPV DNA testing, alone and in conjunction with the liquid-based cytology method in screening for cervical cancer precursors. METHODS: A Markov model was used to describe the course of the cases of CIN2+ that had been detected over a 35 year period. Screening programs started at age 30 and were performed at an interval of once every five years. The model compared three strategies of HPV 16/18 genotyping with reflex cytology triage, high-risk HPV testing alone with referral to colposcopy and cytology-based screening with referral to colposcopy. We assumed the rate of patients lost to follow-up for those referred to colposcopy would be 0%. The clinical parameters were estimated using the data from a study conducted by the Thailand National Cancer Institute. RESULT: Of the three screening strategies evaluated, the high risk HPV DNA testing alone was the most effective for detecting CIN2+ over the 35 year study period. It detected 143 and 510 cases per 100,000 women more than the HPV 16/18 genotyping test and cytology-based strategy, respectively. The HPV genotyping test detected 368 cases per 100,000 women more than the cytology-based approach. In addition, when viewed with five year intervals, there were missed cases totaling approximately half of the detected cases screened by the cytology strategy and 10% of cases detected with screening by the HPV genotyping test. CONCLUSION: This study strongly indicates that HPV/DNA testing is preferable to cytology-based screening for cervical cancer precursors. However, the balance between the benefits, burdens and cost of each screening program should be considered.