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A cancer registry is an information system for collecting, storing and managing data on people with cancer. In the United States, population-based central cancer registries feed national programs (CDC’s National Program of Cancer Registries and NCI’s SEER Program) that monitor how many people are diagnosed, where, and with what outcomes. This page explains what a registry is, what it holds, how researchers turn its counts into rates, and the mistakes that most often distort those rates.
General information only; this is not medical advice. Questions about an individual diagnosis belong with a clinician.
What is a cancer registry? Definition in one paragraph
The National Cancer Institute’s SEER Program describes a cancer registry as “an information system designed for the collection, storage, and management of data on persons with cancer” and says registries play a critical role in cancer surveillance. Surveillance data can also serve as a foundation for cancer research (NCI SEER, read 2026-11-07). In epidemiology terms, a registry is the counting machine behind incidence statistics: it supplies the numerator (new cases) for rates such as new diagnoses per 100,000 people. A clinical data registry is a related but different idea, usually built around a disease, device or treatment rather than a whole population.
What is a cancer registry used for?
The CDC states that registries collect data on new cancer cases, and lists these uses (CDC NPCR, read 2026-11-07):
- monitoring cancer burden and trends over time;
- identifying patterns of cancer and high-risk groups;
- evaluating the effect of cancer prevention and control programs;
- guiding public-health resource planning and priorities;
- advancing research.
What data does a cancer registry collect?
According to the CDC, the data collected for each new case cover the type of cancer, its extent and location, the type of initial treatment, and outcomes. Those items let a registry answer both counting questions (how many) and descriptive questions (where, what kind, how far advanced, what treatment first).
National cancer registry programs: NPCR and SEER
NPCR (CDC)
The National Program of Cancer Registries was created in 1992 by the Cancer Registries Amendment Act (Public Law 102-515) and is authorized under section 301 of the Public Health Service Act (42 U.S.C. 241). It supports central cancer registries in 46 states, the District of Columbia, Puerto Rico, the US Affiliated Pacific Islands and the US Virgin Islands, covering 97% of the US population (CDC, read 2026-11-07).
SEER (NCI)
SEER covers the remaining four states, so together the two programs cover the whole US population (CDC, read 2026-11-07). For SEER’s coverage, data-access tiers and age-adjusted rates, see our guide to the Surveillance, Epidemiology, and End Results (SEER) Program.
Is there a registry for cancer patients?
Yes, in the surveillance sense: central cancer registries record new cancer cases for a population so that burden and trends can be tracked. They are public-health information systems rather than membership lists or support services, and they differ from clinical trial registries, which list studies (see WHO ICTRP). Whether a particular cancer can go into remission, or what support items exist for patients, are clinical or personal questions a registry page cannot answer; ask a treating clinician or a patient-support organisation.
Formula: turning registry counts into a rate
A registry gives counts. To compare places or years, convert counts to a crude incidence rate:
Crude incidence rate = (C / P) × 100,000
- C = number of new cases diagnosed in the population during the period (from the registry);
- P = population at risk over the same period (for a one-year rate, usually the mid-year population);
- 100,000 = the conventional base that makes small rates readable.
Worked example with the arithmetic shown
Illustrative hypothetical numbers, not real registry data. Suppose a registry reports C = 1,200 new cases of a given cancer in one year in a region whose mid-year population is P = 800,000.
- C / P = 1,200 / 800,000 = 0.0015
- 0.0015 × 100,000 = 150
The crude incidence rate is 150.0 new cases per 100,000 population per year. If a second region reports 900 cases among 450,000 people, its rate is 900 / 450,000 × 100,000 = 200.0 per 100,000. The second region has fewer cases but a higher rate, which is why counts alone mislead.
Interpretation: how to read a registry rate
| Situation | Reading guidance (editorial interpretation of the formula) |
|---|---|
| Rate is higher in region B than region A | More new diagnoses per head of population in B. Check age structure before concluding the underlying risk differs. |
| Count rises but the rate is flat | Population growth, not higher risk per person, explains the increase. |
| Rate based on very few cases | Unstable; one or two cases can move it a lot. Pool years or areas. |
| Rate of new cases compared with deaths | Different measures: incidence counts diagnoses, not mortality or case fatality. |
Assumptions and common mistakes
- Incidence versus prevalence. A registry’s new-case counts give incidence. The number of people living with a diagnosis (prevalence) needs survival and follow-up data and a different denominator.
- Crude versus age-adjusted. The crude rate ignores age. Comparing populations with different age structures calls for age-standardised rates.
- Mismatched numerator and denominator. Cases and population must refer to the same area, period and group (for example the same sex and age band).
- Case definition and period. Rates are comparable only when the same cancer definition and diagnosis-year basis are used.
- Coverage and lag. Combined NPCR and SEER coverage is the US population, but a single registry covers only its own area, and recent years may be incomplete until reporting catches up.
- Reading a rate as an individual risk. A population rate describes a group, not one person’s chance of diagnosis. An attack rate is a different, outbreak-oriented measure.
How to report a registry-based rate (APA 7th)
In text: “The crude incidence rate was 150.0 new cases per 100,000 population per year (n = 1,200; population = 800,000).” State the data source, diagnosis years, cancer definition and whether the rate is crude or age-adjusted. Reference list examples (APA 7th edition format):
National Cancer Institute. (n.d.). What is a cancer registry? SEER. https://seer.cancer.gov/registries/cancer_registry
Centers for Disease Control and Prevention. (n.d.). National Program of Cancer Registries (NPCR). https://www.cdc.gov/cancer/npcr/about.htm
How to calculate it in Excel, R or Python
Excel
=B2/C2*100000 (B2 = new cases, C2 = population; returns 150 for 1200 and 800000)R
cases <- 1200; pop <- 800000
rate <- cases / pop * 1e5
rate # 150Python
cases, pop = 1200, 800_000
rate = cases / pop * 100_000
print(round(rate, 1)) # 150.0FAQ
Is there a registry for cancer patients?
Yes: population-based central cancer registries record new cases for surveillance and research. They are not opt-in patient lists, and they differ from clinical trial registries.
What is a cancer registry used for?
Monitoring burden and trends, identifying high-risk groups, evaluating prevention and control programs, planning resources and supporting research (CDC NPCR).
What is a national cancer registry database?
In the US, NPCR (CDC) and SEER (NCI) together cover the whole population: NPCR supports registries in 46 states plus DC and territories, and SEER covers the remaining four states.
Can stage 4 cancer go into remission, and what gifts exist for breast cancer patients?
Those are individual medical or personal questions outside what a registry covers. A treating clinician or a patient-support organisation is the right source.
Where do I look for related measures?
See seroprevalence for another prevalence-type measure and HCUP for hospital discharge data.
Sources
- National Cancer Institute, SEER Program. What is a cancer registry? https://seer.cancer.gov/registries/cancer_registry (read 2026-11-07).
- Centers for Disease Control and Prevention. National Program of Cancer Registries, About. https://www.cdc.gov/cancer/npcr/about.htm (read 2026-11-07).
