Five-year and relative survival
- Measure
Relative survival compares patients with people of the same age and sex without the disease: it isolates the effect of the cancer.
What it is
Observed 5-year survival is the proportion of patients alive 5 years after diagnosis, whatever those who died died of. Relative survival divides that figure by the expected survival of a general-population group with the same age, sex and calendar year, taken from life tables. It thus estimates survival as if the cancer were the only cause of excess deaths, and it is the standard measure of population-based cancer registries.
Formula and reading
- Observed = alive at 5 years / patients diagnosed (all causes of death).
- Relative = observed / expected. 100% = same as the general population; below 100% = excess mortality from the disease.
- Excess mortality at 5 years ≈ 100% − relative survival.
Worked example
- Registry: 500 patients aged 70 with a cancer; 300 are alive at 5 years.
- Observed survival = 300/500 = 60%.
- Life table: people of the same age, sex and year survive 5 years in 85% of cases.
- Relative survival = 60 / 85 = 0.706, that is, 71% (rounded).
- Excess mortality attributable to the cancer ≈ 100 − 71 = 29%.
- Reading: these patients have 71% of the survival they would have without the cancer.
Survival measures in cancer registries
| Measure | What it counts | Needs | Problem |
|---|---|---|---|
| Observed | Deaths from any cause | Follow-up only | In older people it also reflects other causes |
| Relative | Excess deaths against the population | Life tables | Unsuitable tables if patients differ (e.g. smokers) |
| Cause-specific | Only deaths from the cancer | Reliable cause of death | Errors on death certificates |
Markers
- Net survival
- Life table
- 5 years
How to read it
- Compare countries or eras with age-standardised relative survival: populations have different background mortality.
- Better 5-year survival does not prove fewer deaths: also compare population mortality.
- Population-based cancer registries publish it by site, stage, sex and age.
Common pitfalls
- Reading 71% relative survival as 71% of patients alive (that is the observed figure).
- Using general-population life tables for patients with much higher mortality from other causes (smokers): relative survival comes out too low.
- Comparing 5-year survival between places with different screening without thinking of lead time.
Test yourself
Think of the answer, then tap the question to see it.
Observed 60% and expected 85%. Relative survival?
60 / 85 ≈ 0.71: 71% of the survival expected without the cancer.
Where does expected survival come from?
From general-population life tables with the same age, sex and calendar year as the patients.
Why can relative survival exceed 100%?
Because if patients survive better than the general population, the observed/expected ratio is above 1.
What advantage does it have over cause-specific survival?
It does not depend on the cause of death being correctly recorded on the certificate.
Connections
Educational content on epidemiological and statistical methods; the examples use made-up numbers to teach the calculation. Not a clinical or legal guide: current Colombian rules are in the official sources.
Sources: Measures of Cancer Survival (National Cancer Institute, Surveillance Research Program, 2026); SEER Cancer Statistics Review 1975-2016: Introduction (National Cancer Institute, 2019).
Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake
Representative model, for educational purposes only.