The oral cavity has numerous functions. One function is called oral competence, which is the ability to hold food and saliva in the mouth without drooling. The specialized lining of the mouth as well as the many saliva glands provide lubrication which aide in speech, swallowing and in the digestion of food. The grinding and crushing of food, which occurs in the oral cavity, is also important for digestion. Once foods are prepared for swallowing, the oral cavity helps in swallowing as the tongue and the mouth push the food backward towards the swallowing tube – the esophagus. Finally, our highly coordinated and specialized speech, which is so important to communication, would not be possible without the structures of the oral cavity.
Incidence, Epidemiology and Pathology
There is roughly 22,000 new cases per year of cancers of the lip are not included. Between 6,000 and 7,000 deaths per year occur because of oral cavity cancer. As can be easily seen from the review of the anatomy and functions of this area, cancers of the oral cavity left untreated can have devastating effects on critical life functions for people who have this disease. Similarly, choice of treatment must take into account the potential loss of function in this area.
Cancers of the oral cavity may involve any single one of these specialized types of tissue or more than one. As noted, tissues in this area includes bone, teeth, muscle, nerves, a rich supply blood vessels, numerous saliva gland, and the specialized lining called mucosa. Although tumors may arise in any of these types of tissues they are most commonly related to changes in the lining of the mouth.
The most common cancer of the oral cavity is called squamous cell carcinoma and arises from the lining of the oral cavity. Over 95 percent of oral cavity cancers are squamous cell carcinomas and these cancers are further subdivided by how closely they resemble normal lining cells: well differentiated, moderately differentiated and poorly differentiated. Other types of cancers of the oral cavity include cancers of the salivary glands such as mucoepidermoid carcinoma and adenoid cystic carcinoma, sarcomas (tumors arising from bone, cartilage, fat, fibrous tissue or muscle), and melanomas.
Tobacco and alcohol use are the major risk factors for most cancers of the head and neck including the oral cavity. Although the most common use of tobacco in the United States a cigarette smoking, the use of smokeless tobacco, or chew, is associated with oral cavity cancers. The most common site for oral cavity cancer in the United States is the tongue. In other regions of the world, different areas are more commonly affected. In countries such as India, where the use of a specific type of smokeless tobacco and a substance called beetle nut is common, the inner cheek area of the oral cavity is most commonly affected. Although there has been some decrease in the overall numbers of oral cavity cancers and deaths from the disease noted in the last 20 years, the decrease has not been dramatic.
There are many symptoms that raise concern for the possibility of the oral cavity cancer being present. The most common of these is a non-healing wound on the tongue, in the floor of mouth or along the inner cheek. These can be painful, but in some cases do not cause significant discomfort. There may be bleeding from the area which occurs in an “on and off” manner. As the lesions increase in size, more symptoms occur. Complaints may include new or increased pain, pain was swallowing, ear pain, a change in speech, uncoordinated swallowing, or a lump in the neck. The most important factor to note is that sores in the mouth, whether they are related to trauma or to a variation of canker sores, should fully heal within three weeks. If this does not occur attention should be sought and trained professional should evaluate this region.
Evaluation and Diagnosis
Examination will usually be done of the entire head and neck region including the throat nose and ears. Particular attention will be given to feeling the neck to note if there are signs of cancer spread to lymph nodes in the neck called metastases. Once the clinical examination is completed, recommendation may be given to obtain a specialized type of X-ray, such as a CT scan or MRI. One or both of these can may be necessary at each can provide very specific information concerning the extent of disease. The physician may also order an X-ray or CT scan of the chest to see if there is any spread of disease to the lungs, the most common site of spread outside of the neck.
At this point, a biopsy – a small piece of tissue taken from the suspected tumor – is often advised. This tissue is sent to a pathologist to define which types of cells are making up the tumor
Once a full examination has been completed as well as the necessary X-rays and biopsies, the tumor is “staged.” Staging is a well-defined method of describing the exact extent of a specific tumor in an individual patient and then placing that tumor in a specific category. This not only assists in choosing treatment options, but also helps predict how successful therapy will be. There are three categories used to describe the tumor: T (tumor), N (lymph node involvement), M (metastasis – spread to other areas of the body.) This is called the TNM classification system. Tumors of the oral cavity are described by their size. Tumors less than 2 cm are called T1. Tumors that are greater than 2 cm, but less than 4 cm are called T2. Tumors greater than 4 cm are called T3. Any tumor that is deeply invading bone, skin or other areas of the head and neck is labeled T4. Lymph node involvement is labeled as N1 if there is one lymph node less than 3 cm on the same side as the tumor. Lymph node involvement is labeled as N2 if a single lymph node is greater than 3 cm but less than 6 cm, or is on the opposite side of the tumor, or if there are more than one lymph node present. If a lymph node in the neck is greater than 6 cm then it is called N3. The M classification is M0 if there is no evidence of cancer spread elsewhere in the body or labeled as positive if there is evidence of cancer spread to tissues such as the lungs, liver, bones or brain.
Once each part of the TNM classification is completed tumors are then staged into four separate groups: I, II, III, IV. Stages I and II are usually defined as early-stage tumors, whereas stages III and IV are usually defined as advanced stage tumors. Treatment is then based on the stage of the tumor, with more advanced tumors requiring more advanced treatments.
The three main tools for treating cancers of the oral cavity are surgery, radiation therapy, and chemotherapy. For this reason, someone with a cancer of the oral cavity may also meet a specialist from radiation oncology as well as medical oncology. In some cases of advanced cancers of the oral cavity, a specialist in reconstructive surgery may also become involved to assist with specialized reconstruction should it be required.
In general, Stage I and Stage II cancers require one type of treatment, either surgery or radiation therapy, to successfully control the cancer. Advanced Stage III and Stage IV cancers will often require combinations of surgery, radiation therapy and chemotherapy or even the use of all three.
Overall survival rates for any cancer of the oral cavity are about 70 percent five-year survival for stage I or II disease. Five-year survival drops to about 50 percent for stage III cancers and further drops to roughly 35 percent for stage IV cancers.