Research methods: Epidemiologic research in geriatric oncology

Abstract

Despite an increase in the number of studies, there is still a lack of evidence-based medicine for older cancer patients, especially for the nonfit and oldest (80 years and over) cancer patients. Randomized controlled trials (RCTs) are still the gold standard in medicine to assess treatment effectiveness and are considered to be the most robust study design to assess treatment effects. Although RCTs are difficult to perform in older cancer patients, it is important to continue work on developing and using alternative designs. Still, some comparative effectiveness questions cannot be answered by existing RCTs, nor they will be studied in future RCTs because of ethical, financial, or other constraints. Observational studies could be an alternative source of data to compare treatment effectiveness in these questions. However, one of the major challenges in observational data is confounders that affect the outcome of the study and differ in proportion between the two treatment groups; effective methods to control for this confounding are essential in nonrandomized studies. A number of strategies including propensity scores and matching are used to control for measured confounders in observational research; however, control for unmeasured confounders presents a greater challenge; the instrumental variable method might provide a better estimate for treatment effectiveness, providing that certain assumptions are not violated.