Residual of circulating tumor DNA (ctDNA) indicated therapeutic efficacy of sintilimab plus docetaxel in patients with previously treated advanced non-small cell lung cancer (NSCLC).

Abstract

e21207 Background: The synergetic effect of ICIs plus chemotherapy has been demonstrated in first line setting for patients with advanced NSCLC. As previously reported, sintilimab plus docetaxel in advanced Chinese NSCLC pts who had failed first-line chemotherapy showed encouraging efficacy and tolerable safety profile. This exploratory study aims to investigate putative biomarker(s) predicting therapeutic response and long-term outcome for eligible patients. Methods: Advanced NSCLC pts who had failed standard platinum doublet without receiving any ICIs before would receive docetaxel (75mg/m2, day 1) plus sintilimab (200mg, day 3) every 3 weeks for 4-6 cycles followed by sintilimab maintenance until disease progression, unacceptable toxicity, or up to 2 years. Thirty-nine eligible patients received comprehensive genomic profiling of circulating tumor DNA (ctDNA) via a 448-gene panel before treatment. ctDNA from twenty-three patients were dynamically assessed after two courses (at 6th week). Eventually, 22 patients were enrolled into analysis, one patient was lost. White blood cells were used to filter germline variants from ctDNA sequencing data. Results: Of 22 patients with paired ctDNA profiling results at 6th week, 11 patients (50%) were defined as ctDNA residual due to presence of ≥2 somatic variants; Another 11 patients (50%) who had ≤1 somatic variant were defined as non-ctDNA residual. Significant difference of best objective response rate (ORR) (63.64% vs 0%, P=0.0039, two-sided Fisher’s Exact Testing for non-ctDNA residual vs ctDNA residual patients) was observed between these two populations. And numerically higher disease control rate (DCR) was seen in non-ctDNA residual patients (100% vs 63.64%, non-ctDNA residual vs ctDNA residual). Further, patients with ctDNA residual after 2 courses of sintilimab plus docetaxel (at 6th week) displayed higher risk of disease progression [Hazard Ratio (95%CI), 9.91(2.09-46.97), P=0.0038] and inferior prognosis (median PFS, ctDNA residual vs non-ctDNA residual, 3.0 months vs NR, P=0.0007). In addition, mutations of EGFR and LRP1B were enriched in ctDNA residual group. Especially, LRP1B gene mutations associated with shorter PFS period, which should be further investigated. Conclusions: Residual of ctDNA at 6th week was able to indicate inferior response to sintilimab plus docetaxel in patients with previously treated advanced NSCLC. Further validation of ctDNA residual as a robust predictive biomarker is warranted. [Table: see text]