Which survival measure corresponds to having reliable cause of death information (e.g., from clinical trials)?

• A. Observed all-cause survival
• B. Relative survival
• C. Cause-specific survival
• D. Net survival

Answer: (C)

The main idea is measuring cancer-specific outcomes by using accurate cause-of-death information. Cause-specific survival defines the event as death from the cancer and treats deaths from other causes as censored. When cause-of-death data are reliable, this directly isolates the risk of dying from the cancer itself, which is exactly what you want in a clinical-trial setting where death reasons are carefully recorded.

If you didn’t have reliable cause-of-death data, other approaches are used. Observed all-cause survival simply tracks any death, without distinguishing cause, so it doesn’t tell you about cancer-specific mortality. Relative survival and net survival estimate cancer survival by comparing observed outcomes to expected mortality from the general population and don’t depend on knowing the exact cause of death, which can be useful when cause data are uncertain. But with high-quality cause-of-death information, cause-specific survival provides the most direct and interpretable measure of cancer-specific mortality.