People with salivary gland cancer may have questions about their prognosis and survival. Prognosis and survival depend on many factors. Only a doctor familiar with a person's medical history, type of cancer, stage, characteristics of the cancer, treatments chosen and response to treatment can put all of this information together with survival statistics to arrive at a prognosis.
A prognosis is the doctor's best estimate of how cancer will affect a person, and how it will respond to treatment. A prognostic factor is an aspect of the cancer or a characteristic of the person that the doctor will consider when making a prognosis. A predictive factor influences how a cancer will respond to a certain treatment. Prognostic and predictive factors are often discussed together and they both play a part in deciding on a treatment plan and a prognosis.
The following are prognostic factors for major salivary gland cancer. The use of radiation therapy after surgery (post-operative) for high-risk cancers has greatly improved survival rates overall.
Tumour stage is one of the most important prognostic factors. The survival rate decreases as the stage of the cancer increases.
Both grade and tumour type are important prognostic factors. Doctors classify salivary gland tumours by evaluating their behaviour using both the grade and tumour type. Low-grade (slow-growing) tumours have a better prognosis than high-grade (fast-growing) tumours. Some types of salivary gland cancers have a better prognosis than others. For example, acinic cell carcinomas, which tend to be slow growing, have a better survival rate than other salivary gland cancers.
This classification gives us information about prognosis and survival. For example, low-grade acinic cell carcinoma and low-grade mucoepidermoid tumours have a better prognosis than high-grade tumours like adenocarcinoma, malignant mixed tumour, carcinoma ex pleomorphic adenoma, adenoid cystic carcinoma, squamous cell carcinoma, high-grade mucoepidermoid carcinoma and undifferentiated carcinoma.
The prognosis is more favourable when the tumour is in a major salivary gland. Parotid gland cancers have the most favourable prognosis, than the submandibular gland and the least favourable primary sites are the sublingual and minor salivary glands. Minor salivary gland tumours tend to be more aggressive in nature than major salivary gland tumours.
People with salivary gland cancer that has spread to the nearby neck (cervical) lymph nodes have a poorer prognosis than those who have no metastasis. Some tumours are more likely to spread to the lymph nodes in the neck, while other tumours do not spread as often. High-grade mucoepidermoid carcinoma, squamous cell carcinoma and adenocarcinoma are cancers that tend to spread to the neck lymph nodes. Acinic cell carcinoma and adenoid cystic carcinomas do not spread to the cervical lymph nodes as often.
Cancers that spread to distant sites within the body generally have a poor prognosis. The chances of having distant metastasis is greater with increased tumour size (T) and lymph node (N) involvement (T and N classifications).
A salivary gland cancer that causes a loss of facial muscle movement (facial nerve paralysis) is often associated with cancer that has spread to the lymph nodes and distant sites. It usually indicates a poor prognosis. Undifferentiated carcinoma, adenocarcinoma, adenoid cystic carcinoma and squamous cell carcinoma are the types of salivary gland cancers that most often affect the facial nerves.
Men seem to have poorer outcomes than women. The reasons for this are unknown at this time.
The following are prognostic factors for minor salivary gland cancer. The benefit of radiation therapy following surgery for minor salivary gland cancers has not been as clearly defined as it has for major salivary gland cancers.
As with major salivary gland cancers, the grade and tumour type are very important prognostic factors. The extent of the cancer and the location are also important factors.
As there is no formal staging system for minor salivary gland cancers, the impact of stage on prognosis is not as clearly understood. However, the TNM staging system for squamous cell cancers by site does provide prognostic information: the higher the stage, the lower the survival rate.
Minor salivary gland cancers located in the oral cavity have a better prognosis than cancers that start in the paranasal sinuses.
Spread of the cancer to distant sites indicates a poor prognosis and greatly influences survival rates.