Abstract P4-15-10: Initial therapy among patients newly diagnosed with operable early stage human epidermal growth factor receptor 2-overexpressed (HER2+) breast cancer in the US: A real-world retrospective study
Authors: DaCosta Byfield Stacey , Buck Philip O , Blauer-Peterson Cori , Poston Sara A 
Published: May 2015

BACKGROUND: Prognosis and appropriate treatment of breast cancer patients (pts) is influenced by tumor molecular characteristics. However, few existing retrospective studies have investigated the treatment patterns and outcomes of breast cancer pts by tumor biomarkers. The objective of this study was to assess the current real-world treatment patterns associated with resected non-metastatic HER2+ breast cancer in the US.

METHODS: This was a retrospective study of physician-reported clinical information (including date and stage at diagnosis, HER2 status and hormone receptor (HR) status) for commercially insured breast cancer pts from the Oncology Management Registry linked with medical and pharmacy claims from a large, national health plan in the US from 01/2008 to 8/2013. The date of initial diagnosis was the index date. The inclusion criteria were: adult pts (≥18 years old), enrolled in the health plan for ≥6 months after the index date, diagnosed with HER2+ Stage I-III disease, known HR status, received breast cancer specific surgery (mastectomy or lumpectomy) and anti-cancer systemic therapy (ACST) and/or radiation within 6 months of index date. Pts with other primary cancers during the study period were excluded. The initial phase of care included initial therapy (surgery and ACST and/or radiation) until 30 days after the last therapy received (surgery, ACST or radiation) prior to a 90-day gap in treatment. Treatment patterns during the initial phase of care by HR status were examined.

RESULTS: Among 915 pts who met all study criteria, 662 (72%) and 253 (28%) were HR+ and HR-, respectively. Mean age was 52 years (standard deviation=9) and was not significantly different by HR cohort. Approximately 82% (n=749) were diagnosed with Stage I/II disease. Most pts (80%, n=732) received adjuvant therapy only, 19% (n=177) received both neo-adjuvant and adjuvant therapy, and &lt;1% (n=6) were observed to have neo-adjuvant therapy only. Among pts who received neo-adjuvant therapy, mean time from diagnosis to ACST was 21 days (median=21). Among pts who received only adjuvant therapy, mean time from diagnosis to initial breast cancer specific surgery was 24 days (median=20). Overall, 72% of pts received HER2 targeted therapy (69% HR+, 80% HR-; p&lt;0.01) during their initial phase of care. During neo-adjuvant therapy, 72% of pts received trastuzumab (67% HR+, 81% HR-; p&lt;0.05). During adjuvant therapy, 72% of pts received trastuzumab (69% HR+, 81% HR-; p&lt;0.05). The most common neo-adjuvant regimen regardless of HR status was carboplatin+docetaxel+trastuzumab (&gt;40% pts). The most common regimens during the adjuvant therapy period were carboplatin+docetaxel+trastuzumab with or without hormone therapy (∼30% of pts).

CONCLUSION: In this real-world population of commercially insured breast cancer pts treated for operable, early stage HER2+ disease in the US, 28% of pts did not receive targeted therapy. More pts with HR- status received targeted therapy than those with HR+ status. Further studies are warranted to examine whether pts that have not received targeted therapy are eligible and would benefit from an HER2 targeted approach.

Citation Format: Stacey DaCosta Byfield, Philip O Buck, Cori Blauer-Peterson, Sara A Poston. Initial therapy among patients newly diagnosed with operable early stage human epidermal growth factor receptor 2-overexpressed (HER2+) breast cancer in the US: A real-world retrospective study [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P4-15-10.