Introduction to Staging
The concept of describing disease by stage or extent was introduced in 1929 by the League of Nation's World Health Organization. Staging is a common language developed by medical professionals to communicate information about a disease to others. The disease can be any acute or chronic disease such as cancer, diabetes, acquired immunodeficiency syndrome (AIDS), cardiovascular disease, or rheumatoid arthritis. The first primary site so described was cancer of the cervix.
Staging for cancer has evolved over many years. Many groups have developed different staging systems. Some staging systems cover all sites; others are limited to particular ages of patients, histology, sites, study groups, or medical specialties. This learning module briefly discusses common staging schemes and classifications. The three most common staging systems used in hospital and central registries are discussed in detail.
Staging is a shorthand method for describing disease. A coded format, such as a numerical system with increasing values meaning more involvement or severity, allows electronic analysis of cases with similar characteristics.
A short definition for staging is "the grouping of cases into broad categories based on extent of disease." Extent of disease is a detailed description of how far the tumor has spread from organ or site of origin (the primary site). Extent of disease is an anatomic categorization using descriptors to group individual cases in relation to the human body.
As stated in the National Cancer Registrars Association Workbook for Staging Cancer,
Classification is the process of grouping cases based on specific criteria. Classification is an orderly arrangement showing relationships among groups. Classification does not necessarily imply a prognosis.
The relationship between staging, extent of disease and classification is: extent of disease is a type of classification (based on human anatomy) and pertains to an individual case. Staging is coded shorthand or a notation describing disease in more general terms. By staging, characteristics about a case (precise extent of disease information) can be grouped into categories. Thus staging translates extent of disease classification about individual cancers into groups that can be studied or evaluated for prognostic significance.
Elements to be considered in any staging system are the primary tumor site, tumor size, multiplicity (number of tumors), depth of invasion and extension to regional or distant tissues, involvement of regional lymph nodes, and distant metastases.