Abstract 1735: Assessing circulating tumor cells with a nanotechnology-based capture system as a novel biomarker for treatment response and surveillance in patients with oligometastatic solid tumors

Abstract

Abstract Purpose: To prospectively evaluate changes in circulating tumor cells (CTCs) following definitive treatment in patients with oligometastatic solid tumors using a novel nanotechnology-based biomimetric platform. Experiment Procedures: Patients with biopsy proven oligometastatic disease with up to three lesions were eligible if all sites of disease were treated with definitive therapy. Definitive therapy could include fractionated 3D conformal radiation, SBRT, IORT, surgical metastatectomy, and ablative procedures including microwave ablation. Patients initially presenting with oligometastatic disease were eligible if they had less than 3 lesions including the primary tumor. At least one lesion had to be treated with radiation. CTCs were enumerated from whole blood using the Onco-Sense CTC capture system which utilizes E-selectin and dendrimers functionalized with three cancer-specific antibodies (aEpCAM, aHER-2, aEGFR). Whole blood was collected from patients prior to starting treatment (baseline), mid-treatment, end of treatment, within 12 weeks of finishing treatment, and then every 3 months in follow up. We then assessed changes in CTCs with treatment and looked for associations between baseline CTCs, changes during treatment, and post-treatment changes with clinical outcomes. Results: We have currently enrolled 24 patients. The majority of patients (20) had a single site of disease treated with radiosurgery. Sites of metastasis include bone, lung, and lymph nodes. Primary histologies include lung, breast, melanoma, prostate, RCC, colorectal cancer, and SCC of the head and neck. CTCs were detected in 100% of patients at baseline and decreased with treatment from a mean of 45 CTCs/mL pretreatment (range 3-99) to 14 CTCs/mL post-treatment (range 3-59). Post-treatment CTCs are available for 14 patients with a median follow up of 10.3 months. Ten of 14 patients remain clinically NED and post-treatment CTCs are lower than baseline in 13/14 of these patients. There have been 4 clinical failures and CTCs increased with or before radiographic progression in all 4 patients. Three of the failures occurred at least 3 months after initial complete responses to treatment and CTCs increased by a median 3.4-fold over post-treatment levels in these patients. One patient progressed before the first post-treatment follow up and CTCs increased from 7 to 22 CTCs/mL from baseline to post-treatment. Conclusions: We showed here that we could enumerate CTCs in 100% of patients with oligometastatic disease using a novel CTC capture system. CTCs decreased with treatment and all clinical failures were preceded by significant rises in CTCs. Our preliminary data suggest that enumeration of CTCs by Onco-Sense may provide a novel biomarker for assessing treatment response and/or post-treatment surveillance for patients with oligometastatic solid tumors. Note: This abstract was not presented at the meeting. Citation Format: Joseph M. Caster, Kyle Wang, Bhisham Chera, Sin-Jun Park, Seungpyo Hong, Andrew Z. Wang. Assessing circulating tumor cells with a nanotechnology-based capture system as a novel biomarker for treatment response and surveillance in patients with oligometastatic solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1735. doi:10.1158/1538-7445.AM2017-1735