intervention by the quality of life during those years. QALYs can provide a common unit for comparing cost-effectiveness across different interventions and health problems. Analogous units include disability-adjusted life-years (DALYs) and healthy-years equivalents (HYEs).

Randomized controlled trial (RCT)—a true prospective experiment in which investigators randomly assign an eligible sample of patients to one or more treatment groups and a control group and follow patients’ outcomes (also known as a randomized clinical trial).

Relative value unit (RVU)—a comparable service measure used to permit comparison of the amounts of resources required to perform various health care services. It is determined by assigning weight to such factors as personnel time, level of skill, and sophistication of equipment required to render patient services.

Response rate—the percentage of patients in whom treatment results in a significant change in the clinical endpoint of interest.

Standardized patient—an individual who is trained to act as a real patient in order to simulate a set of symptoms or problems.

Statistical power—the probability of detecting a treatment effect of a given magnitude when a treatment effect of at least that magnitude truly exists.

Surrogate endpoint—a biomarker that is intended to substitute for a clinical endpoint in a therapeutic clinical trial and is expected to predict clinical benefit (or lack thereof) based on epidemiologic, therapeutic, pathophysiologic, or other scientific evidence.

Time to tumor progression (progression-free survival)—the time interval from the start of treatment to cancer progression. It is a measure of the clinical benefit from therapy.

Trastuzumab (Herceptin)—see HER2.

Value-based insurance design—a system of patient coinsurance based on the value—not simply the price—of health care services.