Circulating Tumor Cells Failed to Predict Prognosis Following Micro- Wave Ablation of Oligometastasis in EGFR-mutant Non-Small Cell Lung Cancer Patients

Microwave ablation (MWA) in conjunction with EGFR inhibition has been shown to be effective for treating EGFRmutant non-small cell lung cancer patients with oligoprogressive disease. However, patients who will benefit most from MWA is inconclusive. The circulating tumor cell (CTC) count during EGFR-targeting tyrosine kinase inhibitors has been used to predict survival outcomes. This study aimed to explore the prognostic significance of the baseline CTC count and the change in the CTC count during MWA therapy of patients with EGFR-mutant NSCLC. Serial blood samples were taken at baseline (CTC-d0) and on day 28 (CTC-d28) following MWA for detection of CTCs. 36 patients were eligible and thirty-five of these patients had CTC-d0 ≥ 2. Patients were dichotomized as favourable (0-8 CTCs) and unfavourable (≥ 8 CTCs) groups according to CTC numbers. The progression-free survival (PFS) interval for patients in the favourable group at baseline was 8.5 months, similar with the median PFS time of 8.1 months achieved by patients in the unfavourable group ( p=0.231). In addition, patients in the favourable group on day 28 did not exhibit significantly longer median PFS compared with patients in the unfavourable group (8.3 vs. 7.9 months; p=0.147). The overall survival outcome is not mature. In univariate analysis and multivariate analysis, CTC-d0 ≥ 8 vs. CTC-d0<8 and CTC-d28 ≥ 8 vs. CTC-d28 <8 were not significantly associated with poor PFS. This study indicates that the CTC count is not a prognostic factor for PFS outcome following MWA in patients with EGFR-mutant NSCLC.