Abstract 5597: TargetSelector™ CTC technology demonstrates clinical utility in monitoring treatment response in germ cell tumors (testicular cancer)

Abstract

Abstract Background: Liquid biopsy has recently emerged as a minimally invasive and cost effective means to assess cancer biomarkers without the risk of surgical biopsy complications. Using a simple blood draw, circulating tumor cell (CTC) analysis is capable of providing information with implications for diagnostics, prognosis, and treatment decisions of various carcinomas. Serial CTC measurements can aid monitoring disease progression or response to therapy. Biocept's proprietary TargetSelector™ technology captures CTCs and provides assessment of enumeration, protein expression by immunofluorescence, and gene amplifications or translocations via FISH. There is limited data on clinical utility of CTCs in germ cell tumors (GCT). We aim to evaluate the prognostic and predictive significance of CTCs in refractory GCT in an ongoing clinical trial of brentuximab vedontin and bevacizumab in refractory CD 30+ GCT (NCT02988843). CTC enumeration will be performed at baseline, prior to cycle 3 of treatment, and at progression to monitor treatment response in blood from patients with refractory testicular cancer. Methods: Peripheral whole blood samples from refractory testicular cancer patients are collected into Biocept CEE-Sure™ blood collection tubes that are validated to preserve CTCs for up to 96 hours. Biocept's TargetSelector™ platform utilizes a proprietary antibody capture cocktail and microchannel enabling enrichment, enumeration, and CTC analyses which were performed at Biocept's CLIA-certified and CAP accredited laboratory. Results: From a patient with heavily pretreated refractory testicular cancer, serial blood collections were obtained at baseline and prior to cycle 3 (approximately six week interval). Two CTCs were detected at baseline. Prior to cycle 3, there was 1 CTC (corresponding to tumor marker response and CT scan showing stable disease). At progression after cycle 4, the CTC count increased to 4, corresponding with disease progression in tumor markers and CT scan. In this patient, the CTC capture utilizing the TargetSelector™ CTC technology was very predictive of clinical response and progression. Conclusions: Clinical application of Biocept's TargetSelector™ CTC technology enables the sensitive detection of CTCs in testicular cancer. Longitudinal CTC assessment implemented in the clinical setting can be used to assess drug responsiveness and follow disease progression in this rare disease, as well as in more common solid tumor cancers. The TargetSelector™ liquid biopsy platform provides an economical, non-invasive, and reliable means to arm physicians with valuable information for disease management and patient care. Ongoing collection of blood samples and data analysis from patients being enrolled on the study will provide us a better understanding of the potential clinical use of this novel technology in GCT patients. Citation Format: Shilpa Gupta, Benjamin L. Maughan, Cecile Rose T. Vibat, Veena M. Singh. TargetSelector™ CTC technology demonstrates clinical utility in monitoring treatment response in germ cell tumors (testicular cancer) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5597.