INTRODUCTION: Patients in advanced stages of non-small cell lung carcinomas (NSCLC), who and unsuited for targeted biological therapy because of lack of actionable molecular predictors are frequently treated by anti-angiogenic therapy. The effectiveness of such therapy is primarily relying on imaging techniques including CT or hybrid PET/CT evaluating a combination of morphological factors (dimensions and volume) and, more recently, also functional parameters including the metabolic activity, tumor vascularization etc. The ability to track the course of the disease at the same time all of these parameters is prerequisite to enable timely monitoring and therapy change in case of an early detection of resistance. This study was aimed at utility of circulating-tumor DNA (ctDNA) as an tool for monitoring of therapy response. and assessment of phenotypic parameters of the tumor.

PATIENTS AND METHODS: A total of 50 patients with confirmed Stage IV lung adenocarcinomas showing negativity on ALK, BRAF, EGFR, RET, ROS1 and MET predictors were prospectively enrolled into the study. Patients were treated under a standard protocol by a combination of paclitaxes/carboplatin/bevacizumab and followed by dual PET/CT. For each patient cytology tissue sample was subjected to test for a panel of somatic mutations. The found mutations were subsequently detected in ctDNA in plasma extracted from peripheral blood collected prior to therapy start and then in 1-month intervals during the therapy. The occurrence and quantity of ctDNA were correlated with the objective therapy response (RECIST) and to the functional imaging parameters of metabolic activity and vascularization.

RESULTS: ctDNA was initially positive in 29 patients. ctDNA levels closely reflected the response to the therapy with complete or partial remission expressed as reduction or absence of ctDNA, while disease stabilization or progression signaled by persisting or increasing ctDNA levels. There was a borderline correlation between ctDNA and vascularization evaluated by dual PET/CT (p=0.055).

CONCLUSION: In a subset of patients ctDNA can readily serve as a surrogate marker for semi-continuous monitoring of the effect of anti-angiogenic therapy. Work supported by Czech Ministry of Health project AZV 17-30748A.

Citation Format: Marek Minarik, Martin Svaton, Barbora Belsanova, Anastasiya Semyakina, Jan Baxa, Ondrej Fiala, Milos Pesek, Lucie Benesova. Application of a serial liquid biopsy ctDNA assay for monitoring efficacy of anti-angiogenic lung cancer therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 412.