What is oropharyngeal cancer?
Oropharyngeal cancer is cancer of the oropharynx which is the middle part of the pharynx. Pharynx is a hollow tube starting from the nose down the neck into the esophagus which is food passage down to the stomach. Oropharynx is made of base of the tongue, the tonsils, the soft palate (back of the mouth) and walls of the pharynx.
Oropharyngeal cancer occurs when the squamous cells that line the oropharynx undergo mutation and turn into cancerous cells and form squamous cell carcinoma. Oropharyngeal cancer is a subset of head and neck cancer.
What are the risk factors for oropharyngeal cancer?
There are several risk factors which lead to the mutation of the squamous cells into tumor cells and developing into cancer. The risk factors include:
1.HPV infection: There are increasing evidence to support that HPV infection is a predisposing factor to oropharyngeal cancer.
2.Smoking and alcohol consumption
3.Diet low in vegetables and fruits
4.Drinking a stimulant drink called mate in South America
5.Chewing Betel common in Asia
Symptoms of oropharyngeal cancer
The clinical presentation of oropharyngeal cancer may present symptoms of other benign non-cancerous conditions. The symptoms patient may present with include:
1.Pain: behind the sternum
2.Sorethroat: that persists
3.Dysphagia: difficulty swallowing
4.Cough: that persists
6.Lump: at the back of the mouth, throat, or neck.
7.Change in voice
8.Unintentional loss of weight
Clinical signs of oropharyngeal cancer
The clinical physician will ask you questions on your clinical symptoms and perform a physical examination on you. The clinician will look at your general health to see if you are cachectic losing too much weight.
He/she will also examine your oral cavity with mirror and lights and also do a fiber-optic scope to examine the pharynx for any abnormal tissue. If there is a suspicious mass then biopsy will be done and the tissue cells will be sent to the laboratory to check for cancer cells. The neck will also be examined for any palpable lymph nodes which suggest spread of cancer to the lymphatic system.
Diagnostic tests for oropharyngeal cancer
Diagnostic tests will be ordered by your physician to confirm the diagnosis and also for staging of the cancer. The tests include:
1.Nasoscope: a thin tube-like instrument fitted with lens and light for visualization is inserted through the nose down to look at the pharynx to identify any cancerous mass.
2.Biopsy: Any suspicious mass found during nasoscopy will be biopsied and the tissue sent to the laboratory to examine for presence of cancer cells.
3.Chest X-ray: to make sure cancer cells have not spread to the lungs
4.CT Scans: A dye may be injected into a vein or swallowed so that the organs or tissues show up and a series of images of the body is taken to see how extensive the cancer is.
5.Pet Scan: Positron Emission Tomography scan involves injection of small amount of radionuclide glucose (sugar) into the vein and images are taken to identify cancer cells which are active and take up the glucose more than normal cells.
Staging and prognosis of oropharyngeal cancer
Oropharyngeal can spread via 3 ways: through tissue to invade adjacent structures, via bloodstream to other distant organs and also via lymphatic system to the surrounding lymph nodes.
Staging of oropharyngeal cancer will depend on how far the cancer cells have spread (metastasize). The staging of the disease is done via the diagnostic tests mentioned above. The staging of the oropharyngeal cancer not only aid in determining the treatment it also helps predict the prognosis of the disease.
The prognosis which is the survival rate post treatment of oropharyngeal cancer is dependent on the stage of the cancer at presentation, whether it is associated with HPV infection and also the location of the primary tumor. HPV positive cancers have a better prognosis.
Stage 0 (carcinoma in situ): There are abnormal cells found at the lining of oropharynx. These abnormal cells may later turn into cancerous cells.
Stage 1: The cancer cells are ≤ 2cm and is only at the oropharynx.
Stage 2: The cancer cells are ≥ 2 cm but < 4cm and is only at the oropharynx.
Stage 3: Either the cancer cells are ≤ 4cm, has spread to one lymph node at neck at same side of cancer and lymph node is ≤ 3 cm
Cancer cells is > 4cm, or has spread to epiglottis, has spread to one lymph node at neck at same side of cancer and lymph node is ≤ 3 cm
Stage 4A: Cancer has spread to the larynx, lower jaw, or muscles that move the tongue/ for chewing. Cancer may have spread to 1 lymph node on the same side of the neck as the cancer and the lymph node is ≤ 3 centimeters
Cancer has spread to one lymph node (> 3cm ≤ 6cm) on the same side of the neck as the tumor or to more than one lymph node (≤ 6cm) anywhere in the neck AND one of the following is true:
-Cancer in the oropharynx of any size and may have spread to the epiglottis or
-Cancer has spread to the larynx, lower jaw, or muscles that move the tongue/for chewing.
Stage 4B: Cancer surrounds the carotid artery or has spread to the muscle that opens the jaw, the bone attached to the muscles that move the jaw, nasopharynx, or base of the skull. Cancer may have spread to one or more lymph nodes of any size
Cancer of any size and has spread to one or more lymph nodes that are > 6 cm.
Stage 4c: Cancer of any size which has spread beyond the
oropharynx to other parts of the body like the lung, bones or liver.
Treatment of Oropharyngeal Cancer
Treatment of oropharyngeal cancer is dependent on the stage of cancer and also whether the patient is fit for surgery. Treatment modalities include surgery, radiation, and chemotherapy and hyperthermia therapy. Post operation care with regards to speech and feeding also must be taken care of.
The care of oropharyngeal cancer patients is a multi-disciplinary one consisting of head&neck surgeon, medical oncologists, radiation oncologist, speech therapist, dietician and rehabilitation specialist.
Surgery involved removal of the cancerous tissue with a margin of healthy tissue. After surgery, to eradicate any remaining cancer cells, radiation and chemotherapy may be given as adjuvant therapy.
Chemotherapy involves either ingesting of injecting anti-cancer drugs into the body to inhibit the growth of cancer cells by killing them or preventing them from dividing.
Radiation therapy involves high energy X-ray beams targeted at the cancer to stop them from dividing and killing them. Internal radiation uses a radioactive substance inserted to the site of the cancer and target it directly. External radiation uses external machine to direct the radiation to the body.
Radiosensitizers are drugs that make the cancer cells more sensitive to radiation. Combining radiosensitizers and radiation will kill more cancer cells.
Radiation around the neck area may induce radiation on the thyroid gland and cause hypothyroidism. Thyroid function tests should be monitored before and after radiation therapy.
Hyperthermia therapy make uses of extreme heat to damage and kill cancerous tissue. It also makes cancer cells more sensitive to anti-cancer drugs and radiation therapy.
Treatment according to stage of oropharyngeal cancer
Stage 1: Can be treated with surgery or radiation therapy
Stage 2: Can be treated with surgery or radiation therapy
Stage 3: Can be treated with surgery followed by radiation and chemotherapy.
Stage 4: For patients with cancer that can be removed by surgery, post-surgery adjuvant radiation and chemotherapy is added on.
For patients whose cancer is too extensive to be removed surgically, radiation and chemotherapy is the only modality of treatment.
Recurrent cancer: Surgical removal of recurrent cancer cells and also radiation and chemotherapy +/- trial of hyperthermia therapy.
All oropharyngeal patients after treatment must be followed up with their specialists to look out for any recurrence of disease. They will go through careful head and neck clinical examination and sometimes imaging studies as surveillance.
They should be follow up at least monthly for the 1st year, every 2 months for the 2nd year, 3 monthly for 3rd year and 6 monthly thereafter.