Introduction

Collaborative Staging (CS), a new coding system for staging of cancer bringing together the principles of Summary Stage, the TNM categories and stage groupings, and the SEER Extent of Disease coding structure.

The development of the Collaborative Staging Task Force in 1998, began the task of addressing the discrepancies in staging guidelines among the three major staging systems used in the United States. This project is sponsored by the American Joint Committee on Cancer (AJCC) in collaboration with the National Cancer Institute Surveillance, Epidemiology and End Results Program (NCI-SEER); Centers for Disease Control and Prevention National Program of Cancer Registries (CDC/NPCR); National Cancer Registrars Association (NCRA); North American Association of Central Cancer Registries (NAACCR); and American College of Surgeons (ACOS) Commission on Cancer (CoC).

The initial focus of the Task Force was to develop a translation or other method of conversion between the TNM staging system of the AJCC and the SEER Summary Staging System. Such a translation would eliminate duplicate data collection by registrars reporting to clinical (facility based) and epidemiologic (central) registries, address the concerns of clinicians for more clinically relevant data as well as the public health sector's concerns about data reproducibility over time, and provide a higher degree of compatibility between the systems that would expand data-sharing opportunities.

The Collaborative Staging System is a carefully selected set of data items that describe how far a cancer has spread at the time of diagnosis. Most of the data items have traditionally been collected by some cancer registries, including tumor size, extension, lymph node status, and metastatic status. New items were created to collect information necessary for the conversion algorithms, including the evaluation fields that describe how the collected data were determined, and site/histology-specific factors that are necessary to derive the final stage grouping for certain primary cancers. In addition to the items coded by the registrar, this unified data set also includes several data items derived from the computer algorithms that classify each case in multiple staging systems: the sixth edition of the AJCC TNM, Summary Stage 1977 (SS77), and SEER Summary Stage 2000 (SS2000).

AJCC TNM staging provides forward flexibility and clinical utility for individual cancer cases. TNM is dynamic and is changed periodically to meet the decision-making needs of clinicians regarding appropriate treatment methods and the evaluation of their results. The AJCC TNM staging system uses three basic descriptors that are then grouped into stage categories. The first component is "T," which describes the extent of the primary tumor. The next component is "N," which describes the absence or presence and extent of regional lymph node metastasis. The third component is "M," which describes the absence or presence of distant metastasis. The final stage groupings (determined by the different permutations of "T," "N," and "M") range from Stage 0 through Stage IV. The stage group is generated when specific criteria are met in the TNM system, for example, prostate cancer stage grouping will only be generated for adenocarcinomas. When a case does not meet the criteria for stage grouping, the result will be reported as not applicable (cannot be generated). An example of this type of case is a leiomyosarcoma of the uterus, which is specifically excluded from TNM staging in both the uterus and the soft tissue sarcoma chapter. The Collaborative Staging System is based on and compatible with terminology and staging in the sixth edition of the AJCC Cancer Staging Manual,¹ published in 2002. The general rules of the TNM system have been incorporated into the general rules for Collaborative Staging.

Summary Staging provides a measure for cancer surveillance with longitudinal stability for population-based cancer registries. Summary staging is a single digit system and has few categories: in situ, local, regional to lymph nodes, regional by direct extension, both regional lymph nodes and regional extension, regional not otherwise specified, and distant. It is less complex than other staging systems and was written for registrars and epidemiologists who wanted some information on stage but did not wish to collect the more detailed EOD or TNM system. Summary Staging can be useful when a series of cases is so small that only general categories produce enough data for meaningful analysis. The version of Summary Staging commonly used dates from 1977²; the site-specific sections were revised and updated in a new edition published in 2001³.

The Collaborative Staging System uses a modified EOD format to collect information about each case. The SEER Extent of Disease (EOD)⁴ coding system provided longitudinal stability for epidemiological and cancer control studies. More detailed than the Summary Staging System, EOD was developed to assure consistency over time as other staging systems changed. EOD also allows collected data to be collapsed into different and previous staging systems. SEER EOD is a five-field, 10 digit system: tumor size (3 digits), extension of the primary tumor (2 digits), regional lymph node involvement (highest specific lymph node chain involved by tumor) (1 digit), the number of pathologically reviewed regional lymph nodes that are positive (2 digits), and the number of pathologically examined regional lymph nodes (2 digits).

References

1. AJCC Cancer Staging Manual, Sixth Edtion, American Joint Committee on Cancer; Springer-Verlag New York, New York; 2002

2. Classification for Extent of Disease, Self Instructional Manual for Tumor Registrars, Surveillance, Epidemiology, End Results Program, National Cancer Institute, National Institute of Health; Bethesda, Maryland; 1977.

3. SEER Summary Stage Manual, 2000, Surveillance, Epidemiology, End Results Program, National Cancer Institute, National Institute of Health; Bethesda, Maryland; 2001.

4. SEER Extent of Disease (EOD), Surveillance, Epidemiology, End Results Program, National Cancer Institute, National Institute of Health; Bethesda, Maryland; 1998.

 Revised August 18, 2004

Collaborative Staging