Stage at Diagnosis
Stage measures how far a cancer has spread from its origin. The staging system used by CDC’s National Program of Cancer Registries and the National Cancer Institute’s Surveillance, Epidemiology, and End Results program is called Summary Stage. Summary Stage characterizes invasive cancers as localized, regional, or distant. Localized cancer is confined to the primary site; regional cancer has spread directly beyond the primary site (regional extension) or to regional lymph nodes; and distant cancer has spread to other organs (distant extension) or remote lymph nodes.1 Some cancers are unstaged or stage is unknown or unspecified.
In the U.S. Cancer Statistics Data Visualizations tool, stage is classified using a variable that combines summary stage variables used during different time periods: SEER Summary Stage 2000, Derived SEER Summary Stage 2000, and Summary Stage 2018.
The coding logic for the variable Merged Summary Stage is—
- For NPCR registries—
- If a case was diagnosed in 2018 through 2020, stage at diagnosis is recorded using the Summary Stage 2018 variable value.
- If a case was diagnosed in 2016 or 2017, stage at diagnosis is recorded using the SEER Summary Stage 2000 variable value.
- If a case was diagnosed in 2015, stage at diagnosis is recorded using the Derived SEER Summary Stage 2000 variable value. If the Derived SEER Summary Stage 2000 variable is blank, and the SEER Summary Stage 2000 variable has a valid value, that value is used to populate the merged variable.
- For SEER-only registries (Connecticut, Hawaii, Iowa, and New Mexico)—
- If a case was diagnosed in 2018 through 2020, stage at diagnosis is recorded using the Derived Summary Stage 2018 variable value.
- If a case was diagnosed in 2017, stage at diagnosis is recorded using the Derived SEER Summary Stage 2000 variable value.
For cases diagnosed in 2018 through 2020—
- The category Regional, NOS (code 5) is no longer used. There is an artificial increase in the category Regional by Direct Extension Only (code 2) for brain, CNS Other, and lymphoma cases.
Stage categories are different for two cancer sites. For brain and central nervous system tumors, the regional and distant categories have been combined. For urinary bladder tumors, in situ primaries are included as a category.
Merged Summary Stage data are suppressed for testis cases due to a data quality issue.
Stage distribution data are presented as case counts and percentages for two groups—
- The first group includes localized, regional, distant, and unstaged cases. Including unstaged cases helps to quantify the amount of missing data and enables comparisons with other studies using this same categorization. However, including unstaged cases will underestimate the percentages of the other stage categories.
- The second group includes only the known stage categories (localized, regional, and distant). Excluding unknown stage provides better estimates of the stage category percentages.
Frequencies and percentages are suppressed for groups with fewer than 16 cases. In addition, complementary cell suppression is done to suppress data for both sexes combined if data are suppressed for one sex.