56P Plasma circulating ctDNA: Potential biomarker in non-small cell lung carcinoma and clinical significance

Abstract

enrolled. Relevant demographic data were recorded, including performance status (assessed by Karnofsky performance status [KPS] and European Cooperative Oncology Group [ECOG] scoring system). Epidermal growth growth factor receptor (EGFR) expression was estimated in serum using reverse transcriptase polymerase chain reaction (RT-PCR) at baseline and following four cycles of Carboplatin-Paclitaxel chemotherapy. Response was assessed using the RECIST 1.1 criteria. Objective response rate (ORR) was defined as Complete remission (CR) or partial response (PR) and Disease control rate (DCR) was defined as CR/PR/Stable disease (SD). Kaplan meier curve was used to compare the overall survival (OS) between subjects based on median EGFR expression level as the cutoff. Results: A total of 82 subjects were enrolled. These included 79 (96.3%) males with mean (SD) age of 61.9 (9.8) years and 48.8% having metastatic disease. Majority were current / former smokers (97.6%); 59.7% had KPS ranging between 40-70 and 48.1% had ECOG of 0/II. The baseline mean (± SD) serum EGFR expression was 17.8 ± 9.3 fold increase over control values, with median (min., max.) of 18.2 (4.4, 42.8). Following chemotherapy, ORR and DCR were 59.7% and 77.3% respectively. Significant reduction in EGFR expression was observed with median (min, max.) absolute and percentage reduction of 6.2 fold (−3.1, 33.6), and 54.2 % (−55.6, 78.4) respectively; p < 0.001. No significant association was observed between change in EGFR expression and age, gender, disease stage, performance status, ORR or DCR. Subjects with baseline EGFR expression of greater than 16.0 fold had significantly worse OS than those with <16.0 fold increase. Conclusions: EGFR is over-expressed in advanced squamous cell lung cancer and is significantly downregulated following chemotherapy; additionally, baseline expression is a useful marker of overall survival following chemotherapy. Legal entity responsible for the study: N/A