Correlation of homologous recombination deficiency (HRD) score with response to the first-line treatment of immune checkpoint inhibitors plus chemotherapy in non-small cell lung cancer

e21121 Background: Homologous recombination (HR) gene mutations were reported to be associated with efficiency of immune checkpoint inhibitors (ICIs). However, up to date, no recognized standard has been set up for definition of HR mutation (+), which limited its clinical application. Homologous recombination deficiency (HRD) score reflects genomic scar induced by HR genes alteration and disfunction. Thus, it may be worth to explore whether HRD score could predict the efficacy of ICIs-based therapy. Methods: We collected tumor tissues from metastatic non-small cell lung cancer (NSCLC) patients who received first-line treatment of ICIs combined with platinum-based chemotherapy. HRD score testing were carried by BGI genomic scar analysis kit, which calculates the sum of loss of heterozygosity (LOH), telomeric allelic imbalance (TAI), large-scale state transitions (LST) scores, and corrected by ploidy of tumor samples, through next generation sequencing(NGS) data. The association of HRD score and response to ICIs plus chemotherapy were analyzed. Results: 22 EGFR/ALK wild-type metastatic NSCLC patients were included. The average HRD score was 24.57, varying from -26.37 to 92.34. Threshold traversal was performed based on analysis of the progression free survival (PFS) data from the included NSCLC patients. HRD score 31 or more were define as HRD (+). Kaplan-Meier PFS Survival analysis showed prolonged median PFS (mPFS) in HRD (+) versus HRD (-) NSCLC patients (N/A vs. 7.0 ms, Log-rank P = 0.029; HR 0.20, 95%CI 0.04-0.96, likelihood-ratio P = 0.03). The objective response rate (ORR) was 45.5% (5/11) in HRD(+) versus 27.2% (3/11) in HRD(-) patients. In patients with PD-L1 TPS≥1% (22C3), the mPFS was N/A vs. N/A, and the ORR was 75.0% (3/4) vs. 37.5% (3/8), in HRD (+) vs. HRD(-) patients. In patients with PD-L1 TPS < 1% (22C3), the mPFS was 8.5 ms vs.2.0 ms (Log-rank P = 0.0085; HR 0.08, 95%CI 0.01-0.82, likelihood-ratio P = 0.02), and the ORR were 28.6% (2/7) vs. 0%(0/3), in HRD (+) vs. HRD(-) patients. Conclusions: In addition to PD-L1 expression level, HRD score would be a potential promising biomarker for predicting the efficiency of ICIs plus platinum-based chemotherapy in NSCLC patients.