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TOPLINE:

Low-income women with diabetes were less likely to receive adjuvant radiotherapy and chemotherapy to treat breast cancer, to complete their chemotherapy regimen, and to adhere to endocrine therapy compared with those without diabetes.

METHODOLOGY:

• Diabetes disproportionately affects low-income adults and up to one third of women with breast cancer. Studies have shown women with diabetes are less likely to receive chemotherapy than those without diabetes, but it's unclear whether a similar relationship exists for radiotherapy and endocrine therapy as well as whether these women are less likely to complete their chemotherapy regimen.
• Researchers investigated the association between preexisting diabetes and the receipt of adjuvant therapies in younger Medicaid-insured women with nonmetastatic breast cancer undergoing definitive surgery between 2007 and 2015. Patients had a mean age of 51.4 years; 70% of patients were Black and 21% were non-Hispanic White.
• Among the 3704 women undergoing surgery, nearly 21% had preexisting diabetes, 64% received radiotherapy, 60% underwent chemotherapy, and 68% had endocrine therapy.
• Researchers compared therapy use (yes/no), timely initiation (within 90 days post-surgery), and completion of radiotherapy and chemotherapy, as well as adherence (medication possession ratio of greater than 80%) and persistence (less than 90-consecutive-day gap) of endocrine therapy in the first year of treatment.

TAKEAWAY:

• Among the 2726 women undergoing breast-conserving surgery or with node-negative disease receiving mastectomy, those with diabetes were significantly less likely to receive radiotherapy compared with those without diabetes (odds ratio [OR], 0.67; 95% CI, 0.53-0.86).
• Among the 1990 patients with node-positive, hormone receptor-negative or ERBB2-positive invasive breast cancer, women with diabetes were less likely to receive chemotherapy (OR, 0.67; 95% CI, 0.48-0.93) as well as complete chemotherapy (OR, 0.71; 95% CI, 0.50-0.99).
• Among the 2729 patients with hormone receptor-positive breast cancer, women with diabetes were just as likely to receive endocrine therapy (OR, 0.95) but were less likely to adhere to it during the first year of treatment (OR, 0.71).
• The researchers found no significant associations between diabetes and the timely initiation or completion of radiotherapy, the timely initiation of chemotherapy, or the persistence of endocrine therapy.

IN PRACTICE:

This study found that diabetes was associated with underuse of adjuvant radiotherapy and chemotherapy as well as worse adherence to endocrine therapy among low-income women with breast cancer, the authors said, noting a need to "identify the optimal management of diabetes during breast cancer treatment."

SOURCE:

This study, led by Bayu Begashaw Bekele, MPH, PhD, Washington University School of Medicine, St. Louis, Missouri, was published online earlier this month in JAMA Network Open.

LIMITATIONS:

The inclusion of patients younger than 65 years enrolled in Medicaid could limit generalizability. Adherence and persistence and continuation of endocrine therapy in the first year of treatment might not reflect the long-term association between diabetes and endocrine therapy. The administrative claims used to define the completion of therapies might not be accurate. Additionally, physician characteristics, potentially contributing to treatment choice and completion, were not accounted for.

DISCLOSURES:

The study was supported by the National Cancer Institute and the American Cancer Society. The authors did not report any conflicts of interest.