148 HPV, HIV, and Cancer: A Global Challenge

The seminal discovery that human papillomavirus (HPV) infection causes cervical cancer provides an opportunity for prevention by vaccination and new screening approaches. Approximately 600,000 new cancer cases per year are attributable to HPV worldwide of which about half million in less developed countries (de Martel et al, Lancet Oncology, 2012). These cancers include all cervical cancers, the vast majority of anal cancers and approximately half of cancers of the vulva, vagina, and penis. In the head and neck, HPV is clearly involved in a fraction of cancer of the oropharynx that varies between 10% and 70% by geographic area and the burden of cancer caused by tobacco use. Most HPV infection is harmless and clears spontaneously but persistent infection with high risk HPV (notably type 16) is one of the most powerful human carcinogens. HPV disrupts normal cell cycle control promoting uncontrolled cell division and the accumulation of genetic damage. Two effective prophylactic vaccines composed of HPV-16/18 and HPV-16/18/6/11 virus like particles have been introduced in many developed countries as a primary prevention strategy. HPV testing is clinically valuable for secondary prevention in triaging low grade cytology and as a test of cure following treatment. More sensitive than cytology, primary screening by HPV testing could allow screening intervals to be extended. If these prevention strategies can be implemented in developing countries, many thousands of lives could be saved. HIV-positive individuals are at increased risk of HPV infection and cancer sites associated with HPV. cART and cervical screening may avoid an increase in cervical cancer in sub-Saharan cancer.