Who is SEER?
SEER stands for Surveillance, Epidemiology, and End Results. It is a program of the National Cancer Institute, part of the US National Institutes of Health, and it began collecting data on January 1, 1973, after the National Cancer Act of 1971.
SEER gathers records from population-based cancer registries that now cover about 46% of the US population. For each cancer it records the type, where it started, how far it had spread at diagnosis, the first treatment, and whether the person is still alive in later years. It is the only comprehensive US source that tracks both stage at diagnosis and survival across whole populations, which is why most survival figures in this explorer come from it. Death counts come from the National Center for Health Statistics.
What does 5-year relative survival mean?
It is the share of people with a cancer who are alive five years after diagnosis, compared with people of the same age and sex in the general population. Comparing the two groups removes deaths that would have happened anyway, so the figure reflects the effect of the cancer itself.
A figure of 91% means people with that cancer are, on average, 91% as likely to be alive in five years as similar people without it. It is not the same as a cure rate. Many people live far longer than five years, and some cancers, such as chordoma, can return after five years.
What do localized, regional and distant mean?
SEER groups cancers by how far they had spread when first diagnosed. Localized means the cancer was confined to where it started. Regional means it had grown into nearby tissue or lymph nodes. Distant means it had spread to faraway organs such as the liver, lungs or bones.
These are not the stage 1 to 4 numbers doctors use, which follow the more detailed TNM system. The share of cases diagnosed at each stage shows how often a cancer is caught early.
Why the survival figures look backward
To know who is alive five years after diagnosis, people must have been diagnosed at least five years ago. The most recent figures cover people diagnosed between 2016 and 2022, and some cards use earlier periods where that is the latest published breakdown. Treatments have improved since then, so people diagnosed today may do better than these numbers show.
These are averages across large groups. They cannot predict what will happen to one person, whose outlook also depends on age, overall health, the tumor's biology and how it responds to treatment.
Where the case and death numbers come from
Each January the American Cancer Society projects how many new cases and deaths to expect that year, using registry data and national death records. The 2026 numbers on each card are those estimates. Colon and rectal cancer deaths are reported together because death certificates often record one as the other.
For colon cancer, rectal cancer, chondrosarcoma and chordoma, SEER's own summary pages do not publish survival separately, so those cards use the American Cancer Society's analysis of SEER data. Each card footer names its source and period.
What do trial phases mean?
The live list of recruiting studies comes from ClinicalTrials.gov, the registry run by the US National Library of Medicine. Recruiting means the study is enrolling now.
- Phase 1
- Tests safety and the right dose of a new treatment in a small group of people.
- Phase 2
- Checks whether the treatment works against a specific cancer and continues to study safety.
- Phase 3
- Compares the new treatment with the current standard in hundreds or thousands of people. Results usually decide approval.
- Phase 4
- Follows an approved treatment in wider use to learn more about long-term benefits and risks.
A listing is not an endorsement and does not mean someone is eligible. The trials that changed care on each card are selected by ROMbug Bio from published results, dated by their key publication.
Using this information
The explorer is for information and education. It is not medical advice. Decisions about screening, diagnosis and treatment should be made with a doctor who knows your situation. Questions about the explorer: support@rombugbio.com.
