Background : Staging : Treatments : Radiation Therapy

BACKGROUND:

Anatomy:

The pharynx is the part of the upper aerodigestive tract that lies behind the oral cavity and nasal cavity and above the food pipe and windpipe (esophagus and trachea).  The pharynx is divided into three parts.  The nasopharynx lies behind the nose.  The oropharynx lies behind the oral cavity and includes the tonsils, base of the tongue, and posterior wall.  The hypopharynx is below the oropharynx and lies above and behind the voice box (larynx). 

Epidemiology:

Cancer of the pharynx is, in most cases, caused by tobacco products.  Heavy alcohol use is also a contributing factor in many patients. In fact pharyngeal cancer is very rare in persons who have never used tobacco products or alcohol on a daily basis.

STAGING:

The staging of pharyngeal cancer is based on three factors.  The first of these is the size and degree of spread of the primary cancer itself.  The second is the degree in which lymph nodes are involved.  The third is the presence or absence of distant spread in other parts of the body.

Stage I cancer means that the disease is still quite small.  For cancer of the hypopharynx and oropharynx this means the disease is less than 2 cm (about ¾ of an inch) in diameter.  For nasopharyngeal cancer, this means the disease is limited to just one wall of the nasopharynx. 

Stage II disease is larger than that described above, but still has not spread outside of the pharynx and has not involved any lymph nodes. 

Stage III disease is rather massive within the pharynx or has involved lymph nodes to a limited degree. 

Stage IV means that the disease has more extensively involved the lymph node or  has spread directly into tissue outside the pharynx.  Stage IV also would be the designation for patients whose cancer has metastasized to other parts of the body, such as the lungs. 

TREATMENT OPTIONS:

Surgery:

Surgery is an effective way to treat Stage I and Stage II disease as discussed above.  In some cases, surgery can also be effective for stage III disease.  The drawback of surgery, however, is that the patient is often left with an anatomic defect, such as removal of part of a jawbone. 

Radiation:

Radiation therapy is also an effective modality for treating pharyngeal cancer.  Sometimes radiation is given after surgery when there is a high risk of residual cancer.  Radiation can also be used as a treatment in and of itself.  This requires higher doses of radiation with more potential for long-term side effects.

Chemotherapy:

Newer chemotherapy agents are proving helpful in the treatment of pharyngeal cancer.  Chemotherapy is sometimes used in conjunction with radiation (so called concomitant treatment).  In this case, the chemotherapy functions to sensitize the cancer cells to the effect of radiation without sensitizing the normal cells.  Chemotherapy may also be helpful in preventing the spread of cancer to other parts of the body.

RADIATION THERAPY:

Typical course:

Radiation therapy for pharyngeal cancer is given over a course of five to eight weeks.  Typically the patient receives treatment once or twice a day.  Each treatment is relatively mild, consisting of several radiation beams that take about a minute each to treat. 

When radiation therapy is given after surgery (so-called postoperative radiation) the treatment typically takes five to seven weeks. 

When radiation therapy is given as the sole form of treatment, without surgery, more radiation is usually necessary.  Patients often receive up to eight weeks of treatment.  Radiation fields are designed to treat both the primary cancer and any potential areas of lymph node involvement.  Thus, the radiation fields typically cover much of the throat and neck.  The radiation fields are designed with the aid of computers so as to maximize doses to the areas where the tumor is located, while minimizing doses to critical normal structures, including the teeth, jawbone, ears, brain, and spinal cord. 

In many patients there is a “cone down” procedure done during the last two weeks of treatment.  This means that the area irradiated is reduced in size, which, in effect, gives extra radiation to where it is most needed, usually where the primary cancer is located.

Side-effects:

The side effects of radiation can be considered in two separate categories.  The first category is short term reactions, which occur during or shortly after radiation therapy.  The second category is chronic side effects, which can develop years after the radiation is finished.

Short-term side effects of radiation therapy include mucositis and irritation of the skin.  Mucositis is often the most troubling side effect for the patient.  A rather severe sore throat sometimes develops.  The sore throat can be symptomatically treated with numbing medicines.  Anti-yeast medications are also helpful.  

In some cases, the sore throat is bad enough to impede adequate nutrition, at which point the radiation oncologist may recommend a feeding tube.  This tube is placed by a PEG method whereby a gastroenterologist inserts a soft rubber tube directly through the abdominal wall into the stomach.  Specially trained nurses come to the patient’s home to help the family learn how to give canned nutritional supplements through the tube. 

Skin reaction during radiation is usually not severe.  There are a variety of skin creams which can be quite helpful.  The simplest of these contain aloe and can be bought over the counter at any pharmacy.  More effective, in some cases, is Silvadene, a special-prescription-only preparation designed for burn patients.

The acute side effects mentioned above improve after the radiation is finished.  Of more concern, however, are chronic side effects, which develop months to years after the radiation is finished.

Chronic side effects cause more concern than acute side effects because they are sometimes permanent.  The most common chronic side effect is dry mouth, which is due to lack of saliva production caused by damage to the salivary glands by the radiation.  Artificial saliva can be prescribed, but most patients prefer to just carry around a bottle of water. 

The most severe chronic side effect from radiation in this region is damage to the spinal cord.  The radiation oncologist takes great care to avoid this side effect by minimizing, to the greatest extent possible, the amount of radiation to the spinal cord.  By carefully using precise techniques, this risk of damage to the spinal cord is less than 1%.  Damage to the spinal cord is devastating and can lead to paralysis, but it is very rare.  When compared to the risk of progressive cancer, this risk is considered acceptable by most patients. 

Another risk of radiation therapy is damage to the jawbone (mandible).  The radiation oncologist will take care to control the dose to the mandible as much as possible. Unfortunately, however, the pharynx and its draining lymph nodes are adjacent to the mandible, and therefore, it is not possible to completely exclude radiation to the mandible.

Careful attention to dental care is important in minimizing the risk of damage to the jawbone.  Patients with pharyngeal cancer are often evaluated by a dentist or oral surgeon prior to initiation of radiation.  Sometimes it is advisable to remove damaged teeth ahead of time.  In other cases, fluoride treatment may be prescribed.

If dental work is necessary after radiation to the pharynx, it is often advisable to consider hyperbaric oxygen.  Hyperbaric oxygen involves high-pressure treatment for several weeks prior to dental extraction or other major dental work.  In doing so, the risk of damage to the jawbone is lessened. 

While these side effects of radiation are a concern to both the patient and his physician, many techniques have been developed over the past 75 years to minimize the risks.  It is now often very beneficial to administer radiation therapy to patients with pharyngeal cancer.  The disease can be cured with a reasonably low risk of the side effects mentioned above.

Peter H. Blitzer, MD, FACR, FACRO