Impact of dual Medicare and Medicaid eligibility status on mortality for cancer patients across hospital types in the USA:
a retrospective cohort study

Background: Cancer patients with dual eligibility (DE) status for Medicare and Medicaid represent a vulnerable population. How and to what extent differences in long-term mortality apply in oncology and across hospital types are not well understood. The objective of this study is to quantify differences in mortality by DE status and assess whether differences vary by hospital type.

Methods: Retrospective cohort study of US cancer patients aged 66 years and over with fee-for-service (FFS) Medicare, using claims from January 2014 to December 2017 and vital status data through October 2022. Exposures included DE status (DE, Medicare only) and hospital type. The outcome of all-cause mortality was analyzed using Cox proportional hazards models and unadjusted Kaplan-Meier survival curves. We conducted a sensitivity analysis for patient subgroups with different expectations regarding whether cancer or non-cancer mortality would dominate.

Results: There were 1,162,442 beneficiaries: 14.1% were DE. The mean age was 76.5±7.2 years; 47.9% were women, and 14.4% were non-White. Combined across hospital types, patients with DE status had a lower predicted survival based on unadjusted Kaplan-Meier survival plots at the end of year 5, 35.3% [95% confidence interval (CI): 35.1%, 35.5%; P<0.001], compared to Medicare only patients 52.9% (95% CI: 52.8%, 53.0%; P<0.001). While DE and Medicare only patients at cancer specialty hospitals had better outcomes overall, predicted survival was consistently lower for patients with DE status versus Medicare only. DE patients had increased all-cause mortality, hazard ratio of 1.403 (95% CI: 1.394, 1.412; P<0.001). Outcome differences based on DE status were more substantial for low-risk versus high-risk patients, such as non-metastatic vs metastatic patients and prostate vs lung cancer patients.

Conclusions: Compared to Medicare only, DE patients had persistently poorer mortality regardless of hospital type. Improvements in care quality and broader social support systems are likely needed to close the gap.