Presentation (CTI)

OBJECTIVES: This retrospective study used US claims data to develop a treatment-based proxy to identify patients with metastatic triple negative breast cancer (mTNBC) and evaluated the performance of the proxy using electronic medical records (EMR).
METHODS: Between 03/2017-9/2023, patients with ≥1 ICD-10 diagnosis code for BC and metastasis were identified in IQVIA PharMetrics® Plus. Patients with continuous enrollment 6 months prior to (baseline) and ≥3 months after (follow-up) the index date (earliest metastasis code), and no diagnosis codes for other cancers or metastasis within 15 months pre-index were included. A treatment-based proxy was used to ascertain TNBC (i.e., HR- and HER2-) where patients with no claims for treatments indicated for HR+ HER2- (CDK4/6, mTOR, PIK3CA, AKT inhibitors), HR+ (endocrine therapy), or HER2+ mBC during the study period were included. Patients were further linked to IQVIA Oncology EMR for HR and HER2 status based on biomarker testing.
RESULTS: Out of the 32,396 mBC patients identified in claims, 3,651 (11.3%) patients had ≥1 line of therapy and were defined as TNBC using the treatment-based proxy. Of these, 117 (3.2%) patients were linkable to Oncology EMR and 54 linked patients had non-missing HR and HER2 biomarker data. The positive predictive value of the treatment-based proxy was 68.5% for HR- status and 98.1% for HER2- status; 37 (68.5%) patients were classified as having TNBC. In OncEMR, 16 patients (29.6%) had evidence of HR+ HER2- disease and were misclassified by the treatment-based proxy. These patients had claims for chemotherapy and no evidence of targeted therapy during the study period.
CONCLUSIONS: Due to the lack of biomarker data in claims databases, patients with mTNBC are often identified using treatment-based proxies. Although patients with mTNBC can be identified based on the absence of treatments indicated for HR+ or HER2+ mBC, additional criteria are needed to classify patients treated with chemotherapy only.