Treatment Disparities in Radiation and Hormone Therapy Among Women Covered by Medicaid vs Private Insurance in Cancer Registry and Claims Data.

Importance: Prior research has reported undertreatment among patients with cancer who are insured by Medicaid, but this finding may be due, in part, to incomplete data in cancer registries. Objective: To compare disparities in radiation and hormone therapy between women with breast cancer covered by Medicaid and those with private insurance using the Colorado Central Cancer Registry (CCCR) and CCCR data supplemented with All Payer Claims Data (APCD). Design, Setting, and Participants: This observational cohort study included women aged 21 to 63 years who received breast cancer surgery. We linked the CCCR and Colorado APCD to identify Medicaid and privately insured women who were newly diagnosed with invasive, nonmetastatic breast cancer between January 1, 2012, and December 31, 2017. In the radiation treatment analysis, we narrowed the sample to women who received breast-conserving surgery (Medicaid, n = 1408; private, n = 1984) and in the hormone therapy analysis, we selected women who were hormone-receptor positive (Medicaid, n = 1156; private, n = 1667). Main Outcomes and Measures: We used logistic regression to estimate the likelihood of treatment within 12 months to assess whether the results varied between data sources. Results: There were 3392 and 2823 participants in the radiation and hormone therapy cohorts, respectively. The mean (SD) age was 51.71 (8.30) years in the radiation therapy cohort, and 52.00 (8.16) years in the hormone therapy cohort. Among the participants, there were 140 (4%) and 105 (4%) who were Black non-Hispanic, 499 (15%) and 406 (14%) who were Hispanic, 2602 (77%) and 2190 (78%) were White, and 151 (4%) and 122 (4%) were other/unknown in the radiation and hormone therapy cohorts, respectively. A higher percentage of women were aged 50 years or younger in the Medicaid samples (40% vs 34% in the privately insured sample) and identified as non-Hispanic Black (about 7%) or Hispanic (approximately 24%). Treatment was underreported in both sources, but to a lesser extent in the APCD (2.5% and 2.0% for Medicaid and private insurance, respectively) compared with CCCR (19.5% and 13.3% for Medicaid and private insurance, respectively). Using CCCR data, Women with Medicaid insurance were 4 (95% CI, -8 to -1; P = .02) and 10 (95% CI, -14 to -6; P < .001) percentage points less likely to have a record of radiation and hormone therapy compared with privately insured women, respectively. Using combined CCCR and APCD, no statistically significant disparity was observed in radiation or hormone therapy between Medicaid-insured and privately insured women. Conclusions and Relevance: Among women with breast cancer covered by Medicaid vs private insurance, cancer treatment disparities may be overestimated if based solely on cancer registry data.