A Paradigm Shift in Understanding Risk for Cancer in Dentistry

In a recent article in the Journal of the American Dental Association, a study of the literacy of dentists on the topic of oral cancer risk factors, specifically the human papilloma virus, indicated a need for improvement in the knowledge base among dentists about oral cancer risk factors and in how to handle such discussions with patients. 

As someone who was somewhat of a pioneer in the field of adjunctive screening technologies and a strong advocate for early recognition of suspicious tissue changes and early intervention as key components of improving the outcomes of oral cancer, this author was “all over this HPV thing” when it was first identified as a risk factor for oropharyngeal cancer. The fact has remained for nearly a decade that dentists need more information and require better tools to share that information with patients; however, there are significant challenges that must be overcome.

There is first a need to understand the common risk factors that are well-known for oral cancer - specifically squamous cell carcinoma, which is the most common form of cancer discovered in the oral cavity. Classically, the typical oral cancer patient is a male who is older than 50, who smokes and consumes alcohol heavily and frequently. In fact, it has been suggested that tobacco use in combination with alcohol - but not so much independently - accounts for approximately 75 percent of all oral cancer. Poor oral hygiene, lack of regular dental care and the presence of chronic infections like herpes simplex virus, candidiasis, lichen planus and various forms of the human papilloma virus present additional classic risk factors for oral cancer.

It is important to note that these statistics deal with oral cancer, which is anterior to the anterior tonsillar pillar and includes the anterior two-thirds of the tongue, the hard palate and the floor of the mouth. Oropharyngeal cancer - which is often lumped into the “oral cancer” category and involves the tissues posterior to the anterior tonsillar pillars and the soft palate (Figure 1) - requires an endoscopic evaluation by an otolaryngologist and, therefore, may fall outside the scope of general dentistry.

While papillomas and condylomas can and do occur in the oral cavity and may be associated with dysplasia that can progress to squamous cell carcinoma, oral cavity lesions typically are caused by the non-oncogenic varieties of the human papilloma virus, 6 and 11. (Figure 2)  

HPV 16 and 18 have been identified as the primary types implicated in cervical and oropharyngeal cancer, but the other oncogenic types that have been identified to date are 31, 33, 45, 52 and 58. Unfortunately, their clinical appearance is unknown and often involves tonsillar crypts and lymphoid tissues that are not easily identifiable by routine clinical examination unless pain, induration, or loss of function has developed. At this point, immediate referral to an otolaryngologist is imperative because the prognosis of oropharyngeal cancer is time dependent. Oncogenic HPV lesions are typically unassociated with epithelial dysplasia.

It has been proposed that open discussions about HPV and its relationship with oral cancer should be a routine activity in the general dental practice as a prudent preventive measure.^i,While this is noble and ethical in this author’s opinion, it appears currently to be outside of social norms for dentists to be having discussions about oral sex practices with patients. It may even prove to be extremely offensive to many patients. This may be a significant reason why most dentists who have been interviewed on this topic do not discuss this topic with their patients routinely.ⁱ 

As an example, there is at least one case where a dentist had his life personally threatened by a father of an adolescent female who presented with a papilloma in her oropharynx, and an appropriate professional discussion occurred between the clinician, the patient and the patient's mother about possible causes of the lesion.^viii  The implication that his daughter would be sexually active at her age was beyond the limits of comprehension by the father; however, the possibility of sexual abuse had to be ruled out. 

In fact, the patient was evaluated and managed by an otolaryngologist, who confirmed the original finding. While the care given was appropriate and timely intervention occurred, it was clear that an alternative approach to the process was necessary that would have still achieved the goal of intervention without the social drama and negative experience for all concerned.

Possibly a more socially acceptable approach to the HPV dilemma in the dental practice would be to parallel that which is typically used regarding herpes labialis. It is well-known that cold sores are a viral infection resulting from close contact with an infected individual and that nearly everyone is exposed to the virus at some point in their life. Discussions occur when a patient presents with an active lesion about preventing spreading the virus through contact through self and others, but seldom is it necessary or even appropriate to discuss how the patient actually got the virus unless the patient asks for an explanation. 

Who would benefit from telling the patient that they likely got the virus from a parent or sibling, and how would it affect the treatment plan? The fact is that they have the virus, and it needs to be managed.

This author has opted to adapt this approach to HPV as well, except that now it is possible to incorporate some basic education into the medical history interview with patient and parent. A simple question about HPV vaccines on the medical history form that is routinely asked of everyone easily opens the door for discussion, when appropriate, in a professional manner.

For example, having a single yes/no question on the form with a date of the vaccination will enable the dentist to enter a discussion about the general benefits of an inoculation, just like a question about cold sores enables the dentist to discuss expectations regarding dental care during active lesions for the protection of the dental staff and the patient and appropriate treatment strategies.

Just as in the case of the herpes virus, it is still essential that the clinician understands how HPV is acquired, spread and functions in histological modification so that if the patient or parent asks, the clinician can provide educated answers; therefore, a basic review of the HPV family is important.

It is important to understand that the oropharynx is comprised of similar tissue to that of the cervix. Therefore, it is reasonable to extrapolate much of the information known about HPV from gynecological research to oral HPV, including the information about vaccines. 

Essentially, like all viruses, HPV infects susceptible host cells - in this case, via contact with infected bodily fluids or contact of lesions with susceptible mucosa. The virus then enters the host cells and then goes into the nuclei of each infected cell to hijack the normal genetic expression of the cell. The oncogenic varieties of HPV specifically transform the epithelial cells in the genital and upper respiratory tracts. The genetic mutations inactivate normal tumor-suppressing protein synthesis and form oncoproteins that stimulate mitosis and proliferation of the host cells and shut down normal cell regulation, such as apoptosis (cell death). In fact, this same process mimics the normal cancerous process, except that there is an external living entity (the virus itself) rather than a carcinogen.ⁱⁱ 

The risk factors for oral cancer now need to be modified by adding the risk factors for HPV infection. ^v  (Table 1.)  It seems that alcohol use remains a risk factor, especially if it is consumed concomitantly with smoking; however, it is interesting that smoking alone may slow the progress of HPV-related cancers. Marijuana use tends to correlate with higher HPV incidence, but this may be due to risky social practices more than the drug itself. However, risky sexual practices create the highest risk factor for HPV infection, including a proportionate risk increase for the number of lifetime sexual partners, the age of first sexual experience with a partner, and unsafe sexual practices - including the use of prophylactics, which have not been proven to be effective against the transmission of HPV. 

The fact that the younger age of sexual contact with a partner, along with the increased risk per sexual partner in the course of a lifetime, create a significant public health concern because of exponential transmission through vicarious exposure. In other words, if an individual who has never been sexually active participates with a partner who has been exposed to three other partners, then the individual potentially now has equivalently been exposed to four partners since HPV can be carried without symptoms.

This cycle continues and increases the need for a vaccine against this potentially deadly disease, because it is nearly impossible to change the behaviors of society entirely, even with diligent training, counseling and phenomenal healthcare. Therefore, there is risk of an epidemic.