Cancer Staging Over Time Fields Database

Over the years, the criteria/definitions for the collection of staging data has changed. A majority of those adjustments are due to changes in the American Joint Committee on Cancer (AJCC) staging manuals, which change every 8-10 years. The Surveillance Research Program (SRP) that oversees the Surveillance, Epidemiology and End Results (SEER) registries, has updated how stage is collected based on the AJCC changes and these updates are reflected in the Research and Research Plus data. These changes can cause differences in the stage distribution, survival and trends over time.

Researchers have been requesting to look at stage over time (covering multiple AJCC editions), but until now, this capability has either been limited, or very complex to implement.

In 2019, the Staging Over Time team at SEER started developing detailed algorithms that would modify the definitions of T, N, M, and Stage Group so that they could be consistent over time. These algorithms take into effect the changes of what is eligible for AJCC staging, based on AJCC 8th edition.

For the current databases, the following schemas have been completed and are ready for review:

• Bladder
• Breast
• Colon/Rectum
• Corpus Adenosarcoma
• Corpus Carcinoma and Carcinosarcoma
• Corpus Sarcoma
• Intrahepatic Bile Duct
• Kidney Parenchyma
• Kidney Renal Pelvis
• Liver
• Lung
• Melanoma Skin
• Oral Cavity (Buccal Mucosa, Floor of Mouth, Gum, Lip, Other Mouth, Hard Palate, Anterior Tongue)
• Pancreas
• Stomach (incl C160)
• Testis

Although SEER staging data is based on AJCC definitions, SEER provides a combined T, N, M and Stage group based on all information available for the patient but does not provide data for specific timeframes (clinical, pathological, neoadjuvant).

For completing the SEER data items related to staging (Extent of Disease (EOD) 1988-2003, 2018+, and Collaborative Stage (CS) 2004-2015), pathological information generally takes priority over clinical information. However, when neoadjuvant therapy is done (followed by surgical resection), the most extensive stage is recorded (which is usually the clinical stage).

Although all schemas follow similar algorithms for staging over time, each schema will have detailed information available on specific changes.

Data available through the Cancer Staging Over Time Fields database

For each of the schemas where AJCC is applicable, the following information will be available for each of the timeframes (long term and short term):

1. EOD Primary Tumor
2. EOD Regional Nodes
3. EOD Mets
4. Summary Stage 2018
5. Derived T
6. Derived N
7. Derived M
8. Derived Stage Group

Timeframes for schemas

There are two major timeframes available: 1992+ and 2004+. Years available are dependent on when the applicable AJCC chapter was implemented, or due to changes between editions that made going back in time more difficult. Each schema will have detailed information on the years available and which AJCC edition is being used over time. Note that data available for 1992+ may be based on a different edition of AJCC compared to data available for 2004+.

1992+ - "Long term fields":

• Due to how stage data was collected prior to 2004, there are some limitations with this data. A separate mets field was not available prior to 2004. If a patient had organ metastasis, that information was collected in EOD extension and the derivation was a TX, M1. If a patient had distant lymph nodes, that information was collected in EOD Lymph Nodes and the derivation was a NX, M1.
• Starting in 2004, a separate Mets field was implemented so that T and N could be collected individually, along with specific metastatic information. In order to make data for 2004 consistent with data 1992+, all cases diagnosed 2004+ that had mets present were changed as follows:
  • Metastasis to organs or carcinomatosis
    • If distant metastasis (bone, brain, lung, liver, other sites, or carcinomatosis) to organs were coded, the derived T value would be converted to TX.
  • Metastasis to distant lymph nodes
    • If distant metastasis to distant lymph nodes were coded, the derived N value would be converted to NX.

2004+ - "Short term fields":

• All these cases have the separate mets at dx field. Cases with metastatic disease (organ or distant lymph nodes) will maintain their original T and N data.

Database Details

There are two Cancer Staging Over Time Fields databases available to request, one with and one without Census Tract Attributes. The need for Census Tract Attributes should be described in the Research Objectives and Study Design section of the application, and the planned use of the attributes should be explained in the Analytic Plan section of the application.

Both databases are available in the Case Listing, Frequency, and Survival sessions in SEER*Stat for the November 2025 data submission. They are identical to the SEER Research Plus databases other than the specialized fields.

1. Cancer Staging Over Time Fields Database
   • This one is linked to county-level attributes, which include county-level SES, rurality, and demographics.
   • Two datasets will be provided to all approved requestors: one that includes all tumor records from 1992-2023 from the SEER 12 registries, and one that includes all tumor records from 2000-2023 from the SEER 17 registries.
   • Both the SEER 12 and SEER 17 datasets include the long-term and short-term stage fields described above.
2. Cancer Staging Over Time Fields with Census Tract Attributes Database
   • This includes cases based on the SEER 17 registries for cases diagnosed 2006-2023.
   • There are no geographic identifiers included in this database due to confidentiality concerns.
   • It does not include Alaska Native Tumor Registry data.
   • This database is based on an older submission of SEER incidence data, which differs from the current Census Tract-level SES and Rurality Database. Therefore, details provided on that page do not exactly match what was used for this database. The census tract variables are generally the same, however, for this database, variables based on census tract 2010 boundaries were used for all years. If you have any questions, please feel free to contact us.

Please cite the SEER Specialized Database name in any publications. The database name can be found in the approval email and in SEER*Stat.

Data Limitations and Analytical Considerations

Modifying definitions over time

For the most part, modifying definitions over time was straightforward based on how EOD and CS were defined. With the older data (1992-2003), there were times when a particular code definition included structures or lymph nodes that were separate codes in later editions. Additional algorithms were put in place to modify the data as much as feasible.

To help with consistency over time, other available data items, not typically used for staging, were used to categorize cases. For example, for EOD Regional Nodes (N), if a NX was derived and there were positive nodes, the N value was changed to match the positive nodes. In this situation, the assumption was made that the data item Regional Nodes Positive was correct. Depending on the schema, other changes like this were made to make the data more compatible over time.

Due to the modifications and algorithms developed, it is not advised to use staging over time for some years, and then the regular data for the remaining years. For example, using Staging Over Time for 1992-2017 data, and then EOD 2018 for data from 2018+. You must use the Staging Over Time algorithms for all years.

Comparing the results from the staging over time algorithms to the unmodified data does show the effects that the algorithms are having. The algorithms smooth out trends over time and make it easier to analyze the data, which is the goal of this project.