Results of clinical trials of chemotherapy agents in cancer patients provide a window into the expected benefits and toxicities of the therapies for similar patients. As such, trial results form the basis of the causal inferences that influence the Food and Drug Administration’s approval of indications and warnings of expected and possible toxicities. Expected benefit is usually estimated through determinations of disease-free survival and/or overall survival of participating patients. Expected toxicities are established from the spectrum of observed toxicities in participating patients.
Unfortunately, results of most clinical trials of chemotherapy in cancer patients probably do not provide a clear window into the expected benefits and toxicities of chemotherapy in the general population of elderly cancer patients. This lack of external validity results not just from the well-known tendency of trial participants to differ from the population from which they are drawn (e.g., to have different personality traits, to be better educated, etc), but also from the underrepresentation of elderly patients and those with medical comorbidity and/or poor-performance status.
The goal of this study is to validate the Center for Medicare and Medicaid Services’s (CMS) Medicare claims as a source of observational data from which to make robust and reliable causal inferences about the chemotherapy utilization and clinical outcomes in elderly Americans with cancer. The study’s specific aims are to:
- create a new dataset through linkage of CALGB clinical trial data to CMS Medicare claims;
- determine the sensitivity and specificity of Medicare claims in capturing the chemotherapy administered to elderly cancer patients;
- determine the sensitivity and specificity of Medicare claims in capturing specific chemotherapy-related toxicities of elderly cancer patients;
- determine the ability of Medicare claims to capture the disease-free survival of elderly cancer patients.
In summary, while more than half of all cancer patients in the United States are diagnosed with their malignancies at or after age 65, far fewer than half of participants in clinical trials of chemotherapy are 65 or older. There is legitimate concern that those elderly cancer patients who do participate in clinical trials are healthier and therefore not representative of the general population of elderly Americans with cancer. Thus, while there is a substantial need for information regarding the expected benefits and toxicities of chemotherapy in the population of elderly cancer patients—many of whom suffer from comorbid conditions that can affect drug pharmacokinetics—there is currently a paucity of such information.
