Abstract P3-10-28: The impact of HER2-directed targeted therapy on HER2-positive DCIS of the breast

Abstract

Abstract Purpose/Objectives: In invasive breast cancer, HER2 is a well-established negative prognostic factor. However, its significance on the prognosis of ductal carcinoma in situ (DCIS) of the breast is unclear. As a result, the impact of adding HER2-directed therapy to HER2-positive DCIS is unknown and is currently the subject of ongoing clinical trials. In this study, we aim to determine the impact of HER2 status on DCIS patient outcomes as well as the possible impact of HER2-directed targeted therapy on survival outcomes for HER2-positive DCIS patients. Materials/Methods: The National Cancer Data Base (NCDB) was used to retrieve patients with biopsy-proven DCIS diagnosed from 2004-2015. Only patients with known estrogen receptor (ER) status, progesterone receptor (PR) status, and HER2 status were included in the analysis. Patients were divided into two groups based on the adjuvant therapy they received: systemic therapy (assumed to be HER2-directed targeted therapy) or no systemic therapy. Statistics included multivariable logistic regression to determine factors predictive of receiving systemic therapy, Kaplan-Meier analysis to evaluate overall survival (OS), and Cox proportional hazards modeling to determine variables associated with OS. Results: Altogether, 1927 patients met inclusion criteria; 430 (22.3%) received HER2-directed targeted therapy, while 1497 (77.7%) did not. Patients who received HER2-directed targeted therapy were likely more likely to be ER-negative. Patients who received HER2-directed targeted therapy had a higher 5-year OS compared to patients that did not (97.7% vs. 95.8%, p = 0.043). This survival benefit remained on multivariate analysis. Factors associated with worse OS on multivariate analysis included Charlson-Deyo Comorbidity Score ≥ 2 and no receipt of hormonal therapy. Conclusions: In the largest study to date evaluating HER2-positive DCIS patients, the receipt of HER2-directed targeted therapy was associated with an improvement in OS. The results of currently ongoing clinical trials are needed to confirm this finding. Citation Format: Lewis GD, Haque W, Farach A, Hatch SS, Butler EB, Schwartz MR, Bonefas E, Teh BS. The impact of HER2-directed targeted therapy on HER2-positive DCIS of the breast [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-10-28.