HPV-positive oropharyngeal cancer

Human papillomavirus-positive oropharyngeal cancer (HPV+OPC) is a subtype of oropharyngeal squamous cell carcinomas (OSCC), associated with the human papillomavirus type 16 virus (HPV16). Historically, cancer of the throat oropharynx (throat) was associated with the use of alcohol and tobacco, but the majority of cases are now associated with the HPV virus. HPV+OPC differs in a number of respects from OPC not associated with HPV (HPV-OPC), and is considered a separate disease. HPV has long been associated with cancers in the anogenital region, but in 2007 it was also recognized as a cause of oropharyngeal cancer. HPV is common among healthy adults and is largely transmitted through sexual contact, but tobacco use increases the risk of cancer. Human papillomavirus-positive oropharyngeal cancer (HPV+OPC) is a subtype of oropharyngeal squamous cell carcinomas (OSCC), associated with the human papillomavirus type 16 virus (HPV16). Historically, cancer of the throat oropharynx (throat) was associated with the use of alcohol and tobacco, but the majority of cases are now associated with the HPV virus. HPV+OPC differs in a number of respects from OPC not associated with HPV (HPV-OPC), and is considered a separate disease. HPV has long been associated with cancers in the anogenital region, but in 2007 it was also recognized as a cause of oropharyngeal cancer. HPV is common among healthy adults and is largely transmitted through sexual contact, but tobacco use increases the risk of cancer. Detection of a tumour suppressor protein, known as p16, is commonly used to diagnose an HPV associated OPC. The extent of disease is described in the standard cancer staging system, using the AJCC TNM system, based on the T stage (size and extent of tumour), N stage (extent of involvement of regional lymph nodes) and M stage (whether there is spread of the disease outside the region or not), and combined into an overall stage from I–IV. In 2016, a separate staging system was developed for HPV+OPC, distinct from HPV-OPC. The historical treatment of OPC was surgical, with an approach through the neck and splitting of the jaw bone, which resulted in a considerable risk of death. Later, radiotherapy with or without the addition of chemotherapy, provided a less invasive alternative, and the results in terms of treating the cancer, were comparable. Newer minimally invasive surgical techniques through the mouth have improved outcomes, and surgery is often followed by radiation and or chemotherapy in high risk cases. In the absence of high quality evidence, management decisions are often based on technical factors, likely functional loss and patient preferences. Some HPV+OPC may first appear in lymph nodes in the neck, without an obvious source (cancer of unknown primary origin) but removal of tonsil tissue from the oropharynx will often show hidden disease. The presence of HPV in the tumour is associated with a better response to treatment and a better outcome, independent of the treatment methods used and a nearly 60% reduced risk of dying from the cancer. Most recurrence occurs locally and within the first year after treatment. The use of tobacco decreases the chances of survival. While most head and neck cancer has been declining with reduced smoking rates, HPV+OPC has been increasing. Compared to HPV-OPC patients, HPV+OPC patients tend to be younger, have a higher socioeconomic status and are less likely to smoke. In addition they tend to have smaller tumours, but are more likely to have involvement of the cervical lymph nodes. In the United States and other countries, the number of cases of oropharyngeal cancer has been increasing steadily, with the incidence of HPV+OPC increasing faster than the decline in HPV-OPC. The increase is seen particularly in young men in developed countries, and HPV+OPC now accounts for the majority of all OPC cases. Attempts are being made to reduce the incidence of HPV+OPC by introducing vaccination that includes HPV types 16 and 18, found in 95% of these cancers, prior to exposure to the virus. Early data suggest a reduction in infection rates. Like other cancers arising in the head and neck region, HPV+OPC may be an asymptomatic incidental finding of an abnormality in the mouth, by the patient or a health professional, present with local symptoms such as difficulties with speech, swallowing, and breathing as well as pain and infection, or as a swelling in the neck if the cancer has spread to lymph nodes there. These may be accompanied by more general symptoms such as loss of appetite, weight loss and weakness. Most mucosal squamous cell head and neck cancers, including oropharyngeal cancer (OPC), have historically been attributed to tobacco and alcohol use. However this pattern has changed considerably since the 1980s. It was realised that some cancers occur in the absence of these risk factors andan association between human papilloma virus (HPV) and various squamous cell cancers, including OPC, was first described in 1983. Since then both molecular and epidemiological evidence has been accumulating, with the International Agency for Research on Cancer (IARC) stating that high-risk HPV types 16 and 18 are carcinogenic in humans, in 1995, and In 2007 that HPV was a cause for oral cancers. Human papillomavirus (HPV)-positive cancer (HPV+OPC) incidence has been increasing while HPV-negative (HPV-OPC) cancer incidence is declining, a trend that is estimated to increase further in coming years. Since there are marked differences in clinical presentation and treatment relative to HPV status, HPV+OPC is now viewed as a distinct biologic and clinical condition. Human HPV has long been implicated in the pathogenesis of several anogenital cancers including those of the anus, vulva, vagina, cervix, and penis. In 2007 it was also implicated by both molecular and epidemiological evidence in cancers arising outside of the anogenital tract, namely oral cancers. HPV infection is common among healthy individuals, and is acquired largely through sexual contact. Although less data is available, prevalence of HPV infection is at least as common among men as among women, with 2004 estimates of about 27% among US women aged 14–59. HPV oral infection precedes the development of HPV+OPC. Slight injuries in the mucous membrane serve as an entry gate for HPV, which thus works into the basal layer of the epithelium. People testing positive for HPV type 16 virus (HPV16) oral infection have a 14 times increased risk of developing HPV+OPC. Immunosuppression seems to be an increased risk factor for HPV+OPC. Individuals with TGF-β1 genetic variations, specially T869C, are more likely to have HPV16+OPC. TGF-β1 plays an important role in controlling the immune system. In 1993 it was noted that patients with human papillomavirus (HPV)-associated anogenital cancers had a 4-fold increased risk of tonsillar squamous-cell carcinoma. Although evidence suggests that HPV16 is the main cause of OPC in humans not exposed to smoking and alcohol, the degree to which tobacco and/or alcohol use may contribute to increase the risk of HPV+OPC has not always been clear but it appears that both smoking and HPV infection are independent and additive risk factors for developing OPC. The connection between HPV-infection and oropharyngeal cancer is stronger in regions of lymphoepithelial tissue (base of tongue and palatine tonsils) than in regions of stratified squamous epithelium (soft palate and uvula). Human herpesvirus-8 infection can potentiate the effects of HPV-16. Risk factors include a high number of sexual partners (25% increase >= 6 partners), a history of oral-genital sex (125% >= 4 partners), or anal–oral sex, a female partner with a history of either an abnormal Pap smear or cervical dysplasia, chronic periodontitis, and, among men, decreasing age at first intercourse and history of genital warts.