The larynx, commonly called the voice box, is subdivided into three parts: the glottis, the subglottis, and the supraglottis. The glottic larynx is that portion which contains the vocal cords. The supraglottic larynx is that portion which lies above the glottis; the subglottis is the portion of the larynx beneath the vocal cords and leading up to the trachea (wind pipe).
Cancers of the larynx account for the majority of head and neck cancers; however, head and neck cancers account for only about 9% of all cancers diagnosed annually.
In the United States, there are more cancers affecting the glottic larynx than the supraglottic larynx. Conversely, in Europe and many other parts of the world, supraglottic cancers greatly outnumber glottic cancers. Cancers of the glottic larynx are more likely to be detected early because even small lesions produce voice changes readily noticeable by the patient and his/her family members; however, patients with smoking-related chronic laryngitis who are used to a chronically hoarse voice may not detect voice changes produced by an early cancer at this location. The supraglottis tends to be a more silent location because tumors here do not affect the voice until they are significantly more advanced. Patients with tumors in this area may present with a sore throat, pain on swallowing (odynophagia), or ear pain (otalgia).
Laryngeal cancers are staged according to the TNM system as explained in the latest manual of the American Joint Commission on Cancer. There is a separate staging system for cancers that affect different subdivisions of the larynx. Subglottic cancer is quite rare and so we will focus on cancers affecting the glottic and supraglottic larynx.
According to the staging system, a tumor is graded on factors related to the location of the primary tumor and assigned a value ranging from T1 to T4. Depending on whether or not there is evidence of cancer spread to the lymph nodes of the neck (regional metastases), the cancer is staged N0-N2. Distant metastatic spread of the cancer to other organs can occur, most commonly to the lungs, liver, and bone. If there are distant metastases present the patient is staged M1, if not, the stage is M0.
Laryngeal Cancer T staging
* T1a: Tumor is confined to one vocal cord with normal mobility
* T1b: Tumor involves both vocal cords but mobility is normal
* T2: Extension of the tumor from the vocal cords to the supraglottic or subglottic larynx or impaired vocal cord mobility
* T3: Tumor is confined to the larynx but there is fixation of the vocal cord
* T4: There is invasion through thyroid cartilage and/ or other tissues beyond larynx (e.g., trachea, thyroid, pharynx, soft tissue of neck).
* T1: Tumor is confined to one subsite of the supraglottic larynx and there is normal vocal cord mobility
* T2: Tumor invades mucosa of more than one adjacent subsite of supraglottis but vocal cord mobility remains normal
* T3: Tumor is limited to the larynx with vocal cord fixation and/or extension to postcricoid area or preepiglottic tissues.
* T4: Tumor invades through thyroid cartilage, and/or extends into soft tissues of the neck, thyroid, and/or esophagus
Staging of regional metastases is as follows:
* N0: No evidence of regional metastases to cervical lymph nodes
* N1: Single neck node up to 3 cm in greatest dimension
* N2: Single node greater than 3 cm (but less than 6 cm), or multiple lymph nodes
* N3: Any node greater than 6 cm in greatest dimension
The stage is then assigned according to the following scheme:
* TNM Stage
* T1 N0 M0 I
* T2 N0 M0 II
* T3 N0 M0 III
* T1-3 N1 M0 III
* T4, N0-N1 M0 IVA
* T1-4, N2 M0 IVA
* T1-4, N3 M0 IVB
* T1-4, N0-3, M1 IVC
In general, the more advanced the overall stage the worse the prognosis. Prognosis is best for those who have no regional metastases (N0) and worst for those who have distant metastases (M1). Cancers of the supraglottic larynx are more likely to have regional neck metastases than are cancers of the glottic larynx.
Early cancers of the glottic or supraglottic larynx can be treated effectively with radiation or surgery. Photodynamic therapy has also been used in some cases, but this is still in experimental stages. Both treatments offer high cure rates and the ability to maintain a good voice quality.
More advanced cancers of the larynx can be treated with surgery or with radiation therapy and chemotherapy. Use of chemotherapy and radiation therapy offers the possibility of retaining the larynx for some patients that may have required a total laryngectomy (total removal of the voice box). However, chemotherapy used with radiation therapy for these more advanced cancers can be very toxic, and some patients may still go on to require removal of the entire larynx.
Because there is a low likelihood of metastatic spread to regional lymph nodes in early glottic cancer, there is no need to prophylactically treat the neck in these individuals. However, in supraglottic cancer prophylactic treatment, surgery or radiation of the neck is almost always indicated because of the high likelihood of spread of the cancer to the regional cervical lymph nodes. In cases where the lymph nodes are clearly involved by tumor, surgery and radiation may both be required.
At present, there is no cure for those who have evidence of distant metastases. However, chemotherapy can sometimes be used in order to slow the growth of cancers with metastatic spread.