Prospective characterization of circulating tumor cells using a nanotechnology-based capture system in oligometastatic patients undergoing definitive radiation therapy.

Abstract

11533 Background: Circulating tumor cells (CTCs) can provide prognostic information in select patients with advanced cancers. We have developed a sensitive and specific CTC capture system (Oncosensor) which may predict clinical outcomes in patients undergoing definitive radiation for head and neck cancers. There is increasing interest in utilizing potentially curative metastasis-directed therapy for patients with oligometastatic solid-tumor malignancies. There is currently no biomarker to predict the success of this approach in most patients. The purpose of this prospective study is to investigate the potential utility of CTCs as a predictive biomarker for patients with oligometastatic cancer undergoing potentially curative therapy. Methods: Eligible patients had a metastatic solid-tumor malignancy with 3 or fewer metastases. All sites of disease were treated with definitive radiation or surgery. Concurrent chemotherapy was allowed. Peripheral blood (7 ml) was collected prior to starting, first week, mid-point, end RT, and every 4 to 12 weeks post RT. CTCs were quantified using the Oncosensor platform. We then assessed correlations between CTCs (baseline, end treatment, and changes during treatment) and clinical outcomes using multivariate analysis. Results: Baseline CTCs were detected in 20/20 enrolled patients with a mean baseline of 32/ml which decreased to a mean of 14/ml at the end of treatment. There was no association between pretreatment CTCs and clinical outcomes (p = 0.81). There was a significant association between post-RT CTCs and PFS (p = 0.039, HR 1.07 per CTC). Our data also suggest that post-treatment CTC monitoring may be able to detect early disease recurrence. Among the 4 patients with documented clinical failures and post-treatment CTC monitoring, all 4 had increases in CTCs with or prior to clinical or radiographic disease progression, with 1.6 to 7.3 fold increase at the time of progression compared to the prior time point. Conclusions: Our pilot data suggest CTCs may provide a predictive biomarker for patients with oligometastatic disease and could potentially provide a novel marker of disease recurrence.