Human papilloma viruses and cancer in the post-vaccine era

Abstract

Human papilloma viruses (HPV) are strong human carcinogens, in fact today they are considered as the second most frequent carcinogen. In the middle of the 1970s the hypothesis that cervical cancer may arise from viruses was established and in the 1990s the relationship between HPV and cervical neoplasia was confirmed. HPV infections are the most common sexually transmitted infections. Specific subtypes of human papilomaviruses are now considered as the etiological agents in nearly all cases of cervical cancer and cervical epithelial neoplasia. Approximately 470,000 new cases and 23,000 deaths of cervical cancer occur each year, with the majority taking place in developing countries. Cervical cancer remains among the three leading causes of cancer deaths among women below the age of 45. Human papilomaviruses are classified into two groups: high-risk (oncogenic) types and low risk types. HPV types 16, 18, 45 and 31 are considered to be the most important oncogenic types. Subtypes 16 and 18 are the causative agents of more than 50% of cervical pre-cancerous lesions, and more than 70% of cervical cancer cases. High risk subtypes are also implicated with anal, perianal and oropharyngeal carcinomas. Recently, the prophylactic bivalent HPV 16/18 and the quadrivalent HPV 6/11/16/18/ vaccines have been approved. The development of prophylactic vaccines against human papilomavirus has been hailed as one of the most significant advances of recent years and it is expected to reduce dramatically the mortality of human papilomavirus associated cancers, but has also given rise to some of the most intense scientific debates.