Medicaid Expansion and Mortality Among Patients With Breast, Lung, and Colorectal Cancer

IMPORTANCE: Medicaid expansion under the Patient Protection and Affordable Care Act may be associated with increased screening and may improve access to earlier treatment for cancer, but its association with mortality for patients with cancer is uncertain. OBJECTIVE: To determine whether Medicaid expansion is associated with improved mortality among patients with cancer. DESIGN, SETTING, AND PARTICIPANTS: This is a quasi-experimental, difference-in-difference (DID), cross-sectional, population-based study. Patients in the National Cancer Database with breast, lung, or colorectal cancer newly diagnosed from January 1, 2012, to December 31, 2015, were included. Data analysis was performed from January to May 2020. EXPOSURE: Living in a state where Medicaid was expanded vs a nonexpansion state. MAIN OUTCOMES AND MEASURES: The main outcome was mortality rate according to whether the patient lived in a state where Medicaid was expanded. RESULTS: A total of 523 802 patients (385 739 women [73.6%]; mean [SD] age, 54.8 [6.5] years) had a new diagnosis of invasive breast (273 272 patients [52.2%]), colorectal (111 720 patients [21.3%]), or lung (138 810 patients [26.5%]) cancer; 289 330 patients (55.2%) lived in Medicaid expansion states, and 234 472 patients (44.8%) lived in nonexpansion states. After Medicaid expansion, mortality significantly decreased in expansion states (hazard ratio [HR], 0.98; 95% CI, 0.97-0.99; P = .008) but not in nonexpansion states (HR, 1.01; 95% CI, 0.99-1.02; P = .43), resulting in a significant DID (HR, 1.03; 95% CI, 1.01-1.05; P = .01). This difference was seen primarily in patients with nonmetastatic cancer (stages I-III). After adjusting for cancer stage, the mortality improvement in expansion states from the periods before and after expansion was no longer evident (HR, 1.00; 95% CI, 0.98-1.02; P = .94), nor was the difference between expansion vs nonexpansion states (DID HR, 1.00; 95% CI, 0.98-1.02; P = .84). CONCLUSIONS AND RELEVANCE: Among patients with newly diagnosed breast, colorectal, and lung cancer, Medicaid expansion was associated with a decreased hazard of mortality in the postexpansion period, which was mediated by earlier stage of diagnosis.