Abstract P2-05-14: New treatment options for metastatic breast cancer revealed by reverse-phase protein microarray and genomic profiling

Abstract

Abstract Background: The optimal treatment strategy for patients with metastatic breast cancer (MBC) is currently unknown. Resistance to standard therapies like anthracyclines and taxanes limit the number of treatment options in many patients to a small number of non-cross-resistant regimens. We hypothesized that genomic and proteomic profiling of clinical MBC samples would identify genomic alterations that are linked to targeted therapies, and that this could facilitate a personalized approach to therapy for our patients. Methods: We retrospectively analyzed 31 consecutive metastatic breast cancer patients that had genomic and/or proteomic studies sent over a 4 month period from February to May 2014. All patients were seen in our Genomic Oncology Clinic and subsequently underwent a rebiopsy of a metastatic site. Formalin-fixed, paraffin-embedded (FFPE) tissue was sent to either Foundation Medicine for genomic profiling, Theranostics for reverse-phase protein microarray, or both. Standard immunohistochemistry for ER, PR, and HER2 was also performed on all patients. Results: Genomic or proteomic alterations were identified in all 31 patients. All patients harbored at least one actionable target and a treatment recommendation for a currently available FDA approved drug or drug combination was able to be suggested in all but one patient. The most commonly observed genomic alterations were within PIK3CA (26%), TP53 (23%), CCND1 (19%), and MYC (16%). Over 30 distinct genomic alterations were identified. Proteomic results were available from 16 patients. Activation of the AKT/mTOR pathway was evident in a majority of patients. A change in HER2 status was also found in 26% of patients. 16% of cases underwent a negative to positive conversion in HER2 status while 10% of cases underwent a positive to negative conversion. It is notable that all 5 patients that underwent a negative to positive conversion in HER2 status had biopsies taken from metastatic disease in the liver. Conclusions: All patients in this retrospective study harbored genomic or proteomic alterations that are associated with targeted therapies. Treatment recommendations were suggested in all but one patient and a majority of patients are receiving the suggested therapy. Our data demonstrate that routine genomic and proteomic analysis in a clinical setting makes a significant positive impact for patients. Citation Format: Casey B Williams, Pradip De, Nandini Dey, Kirstin A Williams, Jessica Klein, Michelle King, Misty Small, Brigitte Cyr, Scooter Willis, Yuliang Sun, Jennifer Carlson, Brandon M Young, Amy Krie, Brian Leyland-Jones. New treatment options for metastatic breast cancer revealed by reverse-phase protein microarray and genomic profiling [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 P2-05-14.