Preexisting Diabetes and Breast Cancer Treatment Among Low-Income Women

Abstract

This cohort study evaluates the associations of preexisting diabetes with radiotherapy, chemotherapy, and endocrine therapy in low-income women with breast cancer.

Key Points

Question

Is preexisting diabetes associated with utilization, timely initiation, adherence, persistence and continuation, and/or completion of adjuvant therapies in low-income women with breast cancer?

Findings

In a population-based cohort of 3704 Medicaid-insured women (aged <65 years) with breast cancer, diabetes was associated with lower likelihoods of radiotherapy use, chemotherapy use and completion, and endocrine therapy adherence. There were no significant differences in utilization and persistence of endocrine therapy, timely initiation of radiotherapy and chemotherapy, or completion of radiotherapy between women with and without diabetes.

Meaning

These findings suggest interventions optimizing diabetes management during breast cancer treatment may also improve cancer care for low-income patients.

Abstract

IMPORTANCE

Diabetes is associated with poorer prognosis of patients with breast cancer. The association between diabetes and adjuvant therapies for breast cancer remains uncertain.

OBJECTIVE

To comprehensively examine the associations of preexisting diabetes with radiotherapy, chemotherapy, and endocrine therapy in low-income women with breast cancer.

DESIGN, SETTING, AND PARTICIPANTS

This population-based cohort study included women younger than 65 years diagnosed with nonmetastatic breast cancer from 2007 through 2015, followed up through 2016, continuously enrolled in Medicaid, and identified from the linked Missouri Cancer Registry and Medicaid claims data set. Data were analyzed from January 2022 to October 2023.

EXPOSURE

Preexisting diabetes.

MAIN OUTCOMES AND MEASURES

Logistic regression was used to estimate odds ratios (ORs) of utilization (yes/no), timely initiation (≤90 days postsurgery), and completion of radiotherapy and chemotherapy, as well as adherence (medication possession ratio ≥80%) and persistence (<90–consecutive day gap) of endocrine therapy in the first year of treatment for women with diabetes compared with women without diabetes. Analyses were adjusted for sociodemographic and tumor factors.

RESULTS

Among 3704 women undergoing definitive surgery, the mean (SD) age was 51.4 (8.6) years, 1038 (28.1%) were non-Hispanic Black, 2598 (70.1%) were non-Hispanic White, 765 (20.7%) had a diabetes history, 2369 (64.0%) received radiotherapy, 2237 (60.4%) had chemotherapy, and 2505 (67.6%) took endocrine therapy. Compared with women without diabetes, women with diabetes were less likely to utilize radiotherapy (OR, 0.67; 95% CI, 0.53-0.86), receive chemotherapy (OR, 0.67; 95% CI, 0.48-0.93), complete chemotherapy (OR, 0.71; 95% CI, 0.50-0.99), and be adherent to endocrine therapy (OR, 0.71; 95% CI, 0.56-0.91). There were no significant associations of diabetes with utilization (OR, 0.95; 95% CI, 0.71-1.28) and persistence (OR, 1.09; 95% CI, 0.88-1.36) of endocrine therapy, timely initiation of radiotherapy (OR, 1.09; 95% CI, 0.86-1.38) and chemotherapy (OR, 1.09; 95% CI, 0.77-1.55), or completion of radiotherapy (OR, 1.25; 95% CI, 0.91-1.71).

CONCLUSIONS AND RELEVANCE

In this cohort study, preexisting diabetes was associated with subpar adjuvant therapies for breast cancer among low-income women. Improving diabetes management during cancer treatment is particularly important for low-income women with breast cancer who may have been disproportionately affected by diabetes and are likely to experience disparities in cancer treatment and outcomes.