Hospital-based health care use correlates with incidence of adverse events among elderly Medicare patients treated in adjuvant chemotherapy trials (Alliance 70802)

ObjectiveMedicare claims can be useful in chemotherapy-related comparative effectiveness research (CER) estimating survival, but methods for estimating patients' treatment morbidity are currently lacking. We sought to determine if patients' health care use in the claims is a marker of treatment morbidity.Materials and MethodsFor 249 elderly Medicare patients with breast or colon cancer who were treated in two adjuvant clinical trials, we merged patients' National Cancer Institute Common Toxicity Criteria for Adverse Events (CTC AEs) trial data with their contemporaneous Medicare claims. We estimated associations of patients' grade ≥ 3 CTC AE counts and their use of two types of hospital-based health care in claims (i.e., emergency room (ER) visits and hospitalizations).ResultsER visits and hospitalizations were significantly positively associated with grade ≥ 3 CTC AE counts incurred by patients during the study. Eight percent of patients without any grade ≥ 3 CTC AEs had one or more hospitalizations during the observation period compared to 43% of patients with three or more grade ≥ 3 CTC AEs (p < 0.01). Those who were hospitalized at least once had more than three times the rate of grade ≥ 3 CTC AEs (IRR 3.70, 95% CI: 2.53–5.40) compared to those who were not. With each hospitalization, the daily incidence rate of any grade ≥ 3 CTC AE more than doubled (IRR 2.10, 95% CI: 1.54–2.86).ConclusionsBecause hospitalization is strongly associated with clinically significant toxicity it may be a useful outcome for Medicare claim-based CER comparing treatment morbidity for elderly patients receiving different adjuvant chemotherapy regimens.