Patterns of locoregional treatment for nonmetastatic breast cancer by patient and health system factors.

BACKGROUND: The purpose of this study was to examine local definitive therapy for nonmetastatic breast cancer with the Patterns of Care Breast and Prostate Cancer (POCBP) study of the National Program of Cancer Registries (Centers for Disease Control and Prevention). METHODS: POCBP medical record data were re-abstracted in 7 state/regional registry systems (Georgia, North Carolina, Kentucky, Louisiana, Wisconsin, Minnesota, and California) to verify data quality and assess treatment patterns in the population. National Comprehensive Cancer Network clinical practice treatment guidelines were aligned with American Joint Committee on Cancer staging at diagnosis to appraise care. RESULTS: Six thousand five hundred five of 9142 patients with registry-confirmed breast cancer were coded as having primary disease with stage 0 to IIIA tumors and were included in the study. Approximately 88% received guideline-concordant locoregional treatment. However, this outcome varied by age group: 92% of women < age 50 versus 80% of women ≥ age 70 years old received guideline care (P < 0.01). Characteristics that best discriminated receipt (no/yes) of guideline-concordant care in receiver operating curve analyses were the receipt of breast-conserving surgery (BCS) versus mastectomy (C = 0.70), patient age (C = 0.62), a greater tumor stage (C = 0.60), public insurance (C = 0.58), and the presence of at least mild comorbidity (C = 0.55). Radiation therapy (RT) after BCS was the most omitted treatment component causing nonconcordance in the study population. In multivariate regression, the effects of the treatment facility, ductal carcinoma in situ, race, and comorbidity on nonconcordant care differed by age group. CONCLUSIONS: Patterns of underuse of standard therapies for breast cancer vary by age group and BCS use, with which there is a risk of omission of RT.