Imaging Tests For Hypopharyngeal And Laryngeal Cancer

Imaging Tests For Hypopharyngeal And Laryngeal Cancer
Image 1 : Hypopharyx And Laryngopharyx Anatomy
Hypopharyngeal cancer is a term used for tumors of a subsite of the upper aerodigestive tract, and like most other subsite designations, the distinction is anatomic rather than pathophysiologic within the group of head and neck malignancies. The hypopharynx is the region between the oropharynx above (at the level of the hyoid bone) and the esophageal inlet below (at the lower end of the cricoid cartilage). Embryologically, the larynx interjects into the hypopharynx anteriorly and is therefore considered a separate structure.

Hypopharyngeal cancers are often named for their location, including pyriform sinus, lateral pharyngeal wall, posterior pharyngeal wall, or postcricoid pharynx (see images below). Most arise in the pyriform sinus. In the United States and Canada, 65-85% of hypopharyngeal carcinomas involve the pyriform sinuses, 10-20% involve the posterior pharyngeal wall, and 5-15% involve the postcricoid area. 

Cancer that arises in the hypopharynx represents approximately 7% of all cancers of the upper aerodigestive tract. The incidence of laryngeal cancer is 4-5 times that of hypopharyngeal cancer. All pharyngeal subsites accounted for approximately 124,000 cancer cases worldwide in 2002.

In a retrospective cohort study, Kuo et al reported a decline in the incidence of hypopharyngeal cancer in the United States by an average of -2.0% annually between 1973 and 2010. The study involved 3958 adults with the disease, with information culled from the Surveillance, Epidemiology, and End Results (SEER) program database.

Patients diagnosed with hypopharyngeal cancer are typically men aged 55-70 years with a history of tobacco use, alcohol ingestion, or both. The combined use of tobacco and alcohol has a synergistic effect on the incidence of hypopharyngeal cancer.

One exception is an increased incidence of postcricoid cancer in women aged 30-50 years with Plummer-Vinson or Paterson-Kelly syndrome. This syndrome includes dysphagia, hypopharyngeal and esophageal webs, weight loss, and iron deficiency anemia. Currently in the United States, because of the reduced incidence of Plummer-Vinson syndrome, postcricoid carcinoma is more common in men. Asbestos may pose an independent risk for the development of hypopharyngeal cancer. 

The etiology of squamous cell cancers is similar for most anatomic subsites. Tobacco and ethanol are the principle carcinogens responsible. Long-term exposure causes progressive cellular dysregulation by alteration of tumor suppressor genes such as TP53, amplification of proto-oncogenes such as cyclin D1, and damage to regulatory factors such as transforming growth factor–beta (TGF-beta) and retinoic acid receptors. The progression from normal mucosa to cancer correlates with accumulation of genetic abnormalities.

The role of human papilloma virus (HPV) in cancers of the hypopharynx is unclear, although it may play more of a role in cancers of the oropharynx and oral cavity. Nonsmokers with cancers of the head and neck are more likely to have detectable HPV, although this is less common than hypopharyngeal cancer in persons who smoke.
  1. Clinically, the mucosa first develops dysplastic lesions that may appear white (leukoplakia) or red (erythroplasia), and with time and continued carcinogen exposure, lesions can develop into frank malignancy.
  2. Nutritional and metabolic deficiencies are implicated in rare instances. Plummer-Vinson syndrome, mucosal webbing of the postcricoid area with iron deficiency, is associated with a higher incidence of cancer in that region. This is most common in women from northern Europe, including nonsmokers. The pathophysiology is not clear.
  3. Genetic factors are under investigation. Heritable polymorphisms of expression of enzymes that activate tobacco-related protocarcinogens (eg, aryl hydrocarbon hydroxylase) and detoxify carcinogens (eg, glutathione S-transferase) have been identified. Certain polymorphisms in the alcohol dehydrogenase genes may increase the risk of oral and pharyngeal cancers related to alcohol consumption. Racial differences in the metabolism of carcinogens may be a possible cause of the increasing incidence in African Americans.
  4. Clinical testing for peripheral blood lymphocyte chromosome fragility shows promise for identifying individuals at high risk of primary and secondary head and neck cancers, but it is still investigational.
  5. Deficient DNA repair mechanisms increase susceptibility to head, neck, and other cancers. Clinically recognized syndromes include xeroderma pigmentosum, Bloom syndrome, ataxia-telangiectasia, and Fanconi anemia. Head and neck cancers are not constituents of the most common cancer family syndromes, which includenonpolyposis colorectal cancer, Li-Fraumeni, or BRCA1/BRCA2 mutation kindreds.

Imaging Tests For Hypopharyngeal 
And Laryngeal Cancer

Imaging tests use x-rays, magnetic fields, or radioactive substances to create pictures of the inside of your body. Imaging tests are not used to diagnose laryngeal or hypopharyngeal cancers, but they may be done for a number of reasons both before and after a cancer diagnosis, including:
  • To help look for a tumor if one is suspected
  • To learn how far cancer may have spread
  • To help determine if treatment has been effective
  • To look for possible signs of cancer recurrence after treatment

1. Computed tomography (CT) scan
The CT scan (also known as a CAT scan) uses x-rays to produce detailed cross-sectional images of your body. Instead of taking one picture like a standard x-ray, a CT scanner takes many pictures of the part of your body being studied as it rotates around you. A computer then combines these pictures into an image of a slice of your body. Unlike a regular x-ray, a CT scan creates detailed images of the soft tissues and organs in the body.

This test can help your doctor determine the size of the tumor, if it is growing into nearby tissues, and if it has spread to lymph nodes in the neck. It may also be done to look for spread of cancer to the lungs.

A CT scanner has been described as a large donut, with a narrow table in the middle opening. You will need to lie still on the table while the scan is being done. CT scans take longer than regular x-rays, and you might feel a bit confined by the ring while the pictures are being taken.

You may be asked to drink 1 to 2 pints of a liquid called oral contrast before the test. This helps outline the digestive tract so that certain areas are not mistaken for tumors. You may also receive an IV (intravenous) line through which a different kind of contrast dye (IV contrast) is injected. This helps better outline other structures in your body. Some people are allergic to the dye and get hives, a flushed feeling, or, rarely, more serious reactions like trouble breathing and low blood pressure. Be sure to tell your doctor if you have any allergies or have ever had a reaction to any contrast material used for x-rays.

2. Magnetic resonance imaging (MRI) scan
MRI scans use radio waves and strong magnets instead of x-rays. The energy from the radio waves is absorbed and then released in a pattern formed by the type of tissue and by certain diseases. A computer translates the pattern into a very detailed image of parts of your body. A contrast material may be injected just as with CT scans, but it is used less often.

Because it provides a very detailed picture, an MRI scan may be done to look for spread of the cancer in the neck. These scans can be very useful in looking at other areas of the body as well.

MRI scans are a little more uncomfortable than CT scans. First, they take longer – often up to an hour. Second, you have to lie inside a narrow tube, which is confining and can upset people with claustrophobia (a fear of enclosed spaces). Newer, more open MRI machines can sometimes help with this if needed, although the images may not be as sharp in some cases. MRI machines make buzzing and clicking noises, so some centers provide earplugs to help block this noise out.

3. Barium swallow
This is often the first test done if someone is having a problem with swallowing. For this test, you drink a chalky liquid called barium to coat the walls of the throat and esophagus. A series of x-rays of the throat and esophagus is taken as you swallow. The barium can help show abnormal areas in the throat.

4. Chest x-ray
A chest x-ray may be done to see if the cancer has spread to the lungs. If any suspicious spots are seen on the chest x-ray, a CT scan of the chest may be needed to get a more detailed picture.

5. Positron emission tomography (PET) scan
For a PET scan, a form of radioactive sugar (known as fluorodeoxyglucose or FDG) is injected into the blood. The amount of radioactivity used is very low. Cancer cells in the body grow quickly, so they absorb large amounts of the radioactive sugar. After about an hour, you will be moved onto a table in the PET scanner. You lie on the table for about 30 minutes while a special camera creates a picture of areas of radioactivity in the body. The picture is not finely detailed like a CT or MRI scan, but it provides helpful information about your whole body.

A PET scan may be used to look for possible areas of cancer spread, especially if there is a good chance that the cancer is more advanced. This test can also be used to help tell if a suspicious area seen on another imaging test is cancer or not.

Some newer machines can do both a PET and CT scan at the same time (PET/CT scan). This lets the doctor compare areas of higher radioactivity on the PET with the more detailed appearance of that area on the CT.

References :
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