Head and neck cancer is diagnosed in approximately 650,000 patients each year worldwide.1 The term head and neck cancer refers to a group of biologically similar cancers originating from the upper aerodigestive tract, including the lip, oral cavity (mouth), nasal cavity, paranasal sinuses, pharynx, and larynx. Oropharyngeal refers to all the structures of the mouth and pharynx, including the tonsils and tongue. Oral squamous cell carcinoma (OSCC) is the most common form of head and neck cancer.2 Seventy-five percent of all OSCCs are attributable to tobacco and alcohol use.3 People who smoke cigarettes are 4 times more likely to develop oral cancer than nonsmokers. Furthermore, individuals who consume alcohol are 3 times more likely than nondrinkers to develop oral cancer.3 According to the Substance Abuse and Mental Health Services Administration, the prevalence of cigarette smoking has decreased among Americans, and alcohol use has also declined since the 1970s.4,5 However despite this, the incidence of oropharyngeal cancers, including cancer of the base of the tongue and tonsils, has increased, especially in younger patients. These trends have led researchers to investigate other potential risk factors.6-8
New studies suggest that there may be an alternative pathway for the development of oropharyngeal cancers. The high-risk types of human papillomavirus (HPV), especially type 16 (HPV-16), are now thought to be potential etiologic agents.2,3 The concept that HPV plays a role in head and neck cancers is not new. This link has been under investigation for at least 20 years.6 This is a worrisome public-health concern because patients with HPV-positive OSCC are 3 to 5 years younger at diagnosis than those with HPV-negative OSCC, and they have a history of high-risk sexual behavior.9-12 Interestingly, patients with HPV-positive OSCC are also less likely to have a history of alcohol and tobacco abuse.3 Therefore, educating patients regarding the disturbing trend of HPV-positive oropharyngeal cancer is important.
INCIDENCE AND PREVALENCE
In the United States alone, an estimated 34,360 people received a diagnosis of oropharyngeal cancer in 2007; of these, 7,550 (5,180 men and 2,370 women) died.13 On average, more than 25% of people who develop oropharyngeal cancer will die of the disease, with only 60% surviving for more than 5 years.14 In fact, oropharyngeal cancer is as common as leukemia and claims more lives than either melanoma or cervical cancer.13
Since the mid 1970s, oropharyngeal cancer rates have increased approximately 15%, with significant disparities in some population groups. For instance, oropharyngeal cancer prevalence is significantly higher in males than in females.14 Prevalence is also higher in Hispanic and black males than it is in white males.14 The risk of oropharyngeal cancer increases with age, and occurrence is highest in persons older than 50 years and peaks between ages 60 and 70 years.14 However, there has been a startling 5-fold increase in the incidence of oral cancer in patients younger than 40 years, many of whom have no known risk factors.4
HPV is associated with 15% to 35% of head and neck cancers worldwide.11 Fifty percent to 90% of OSCCs in the pharynx, tonsil, and tongue are HPV-positive.11 Chaturvedi and colleagues investigated the impact of HPV on the epidemiology of OSCCs in the United States.9 These researchers reported that HPV-positive OSCCs were diagnosed at younger ages than HPV-negative OSCCs (mean age at diagnosis was 61.0 and 63.8 years, respectively) and the incidence increased significantly for HPV-positive OSCC from 1973 to 2004, particularly among younger white men.
Kreimer and colleagues conducted a systematic review of 60 studies and determined that 25.9% of the 5,046 patients with head and neck squamous cell carcinoma (HNSCC) were HPV-positive.2 Furthermore, these researchers noted that HPV-16 was the most prevalent genotype in these cancers, accounting for 86.7% of cases.
Although there is research that supports the association between HPV and oropharyngeal cancers, some studies dispute that relationship. Specifically, controversy exists over the prevalence and significance of HPV in oral tongue cancers (cancer of the anterior two-thirds of the tongue). In a 2008 Mayo Clinic study, researchers examined fresh-frozen tissues from 51 patients with oral tongue cancers.15 Their findings suggest that the incidence of oral HPV in oral tongue cancer was low and was unlikely to play a significant role in the etiology, pathogenesis, and clinical outcomes of oral tongue cancers.15 The authors admit the study was limited by a small sample size and that more research is needed.