Targeting the human papillomavirus for prevention of cervical cancer

University dissertation from Medical Microbiology, Lund University

Abstract: Different types of human papillomavirus (HPV) vary in the extent they cause precursor lesions (CIN) and cancer. There are limited long-term efficacy data on HPV testing in primary screening

Among 72 cervical cancers in Mozambique, HPV 16 and 18 were the most frequent HPV types (69% of cases). Comparing 108 cervical cancers cases and 517 matched controls nested within a population-based cohort in Taiwan, HPV 16 seropositivity implied a 6-fold increased cancer risk. In a cohort of 5696 women in Sweden, HPV types 16, 31 and 33 conveyed the highest risks for future high-grade CIN (CIN 2+), attributing to 33.1%, 18.3% and 7.7% of CIN 2+ cases, respectively. In a pooled analysis of seven European longitudinal studies of HPV-based cervical screening, the cumulative incidence rate of CIN grade 3 or worse (CIN 3+) was higher after 3 years among women with normal cytology than among women with a negative HPV test after 6 years. Finally, in a randomized cervical cancer screening trial in Sweden, adding testing for HPV persistence resulted in a 51% (95% CI: 13-102) increase of CIN 2+ at prevalent screening, which was followed by a reduction of 42% (95% CI: 4-76) of CIN 2+ at incident screening.

In conclusion, HPV-based cervical cancer screening protects against future CIN 2+, and the long-term protective effect should enable extended screening intervals to 6 years. Albeit HPV 16 is the most important carcinogenic HPV type all over the world, different ?high-risk? HPV types convey distinctly different risks for CIN 2+, which should be considered in design of screening tests and vaccines.