HPV-Induced Oropharingeal Cancer
Over the last two decades the incidence of HPV-induced oropharingeal cancer has greatly increased worldwide. Currently HPV-induced oropharingeal cancer accounts for 35% of all head and neck cancer. Risk factors for HPV positive head and neck cancers are young age at first intercourse, high number of sexual partners and oral sex. Typically patients affected by this disease are younger and predominately males.
Screening should be done by an internist by visual oral examination in order to treat precancerous lesions or diagnose the disease early. The most common sites of involvement by HPV induced head and neck cancer are tonsil and base of tongue.
Although there are many human papillomaviruses, HPV 16 accounts for 90% of HPV positive head and neck cancer. HPV positive tumors are more sensitive to radiation and respond better to chemoradiation and targeted therapies. The better response to various treatments is attributed to the different biological and genetic changes that the HPV virus causes to the cancer cells compared to tobacco. No TP53 genetic mutations were seen in the HPV positive tumors and the overall mutation rate was half compared to HPV negative tumors.
After 5 years, the tumor control for HPV-positive tumors was 81% compared to 55% for HPV-negative tumors, and the survival rate was 89% compared to 55% respectively. The platinum agents, the taxanes and the epidermal growth factor inhibitor cetuximab have been effective radiosensitizers. Current studies are testing the efficacy of radiation and cetuximab alone in order to eliminate the toxicity from chemotherapy.
Antiangiogenic treatments and targeted agents (bevacizumab, sunitinib, sarafenib, vandetanib) are currently under investigation. Studies utilizing vaccines targeting oncoproteins expressed by the virus are on-going. It will be interesting to see if the HPV vaccine will have a preventive effect not only on cervical cancer but also head and neck cancer in the coming years.