Background: This study examines the expansion of health insurance coverage in Massachusetts under state health reform as a natural experiment to investigate whether expanded insurance coverage reduced the likelihood of advanced stage colorectal cancer (CRC) and breast cancer (BCA) diagnosis.
Methods: Our study populations include CRC or BCA patients aged 50-64 years observed in the Massachusetts Cancer Registry and Surveillance Epidemiology and End Results (SEER) registries for 2001-2013. We use difference-in-differences regression models to estimate changes in the likelihood of advanced stage diagnosis after Massachusetts health reform, relative to comparison states without expanded coverage (Connecticut, New Jersey, Georgia, Kentucky, and Michigan).
Results: We find some suggestive evidence of a decline in the proportion of advanced stage CRC cases. Approximately half of the CRC patients in Massachusetts and control states were diagnosed at advanced stages pre reform; there was a 2 percentage-point increase in this proportion across control states and slight decline in Massachusetts post reform. Adjusted difference-in-difference estimates suggest a 3.4 percentage-point (P=0.005) or 7% decline, relative to Massachusetts baseline, in the likelihood of advanced stage diagnosis after the reform in Massachusetts, though this result is sensitive to years included in the analysis. We did not find a significant effect of reform on BCA stage at diagnosis.
Conclusions: The decline in the likelihood of advanced stage CRC diagnosis after Massachusetts health reform may suggest improvements in access to health care and CRC screening. Similar declines were not observed for BCA, perhaps due to established BCA-specific safety-net programs.