Genomic profiling of relapsed small cell lung cancer reveals potential pathways of therapeutic targets

Background: Almost all patients with small cell lung cancer (SCLC) relapse. The therapeutic options of relapsed SCLC are limited, and the clinical outcomes are poor. Thus, genomic profiling of relapsed SCLC patients may help to develop more effective therapeutic options.Methods: We collected blood specimens and follow-up information from a consecutive cohort of 31 patients diagnosed with relapsed SCLC in Zhongnan Hospital, Wuhan University, between 2018 and 2019, to analyze the comprehensive genomic profiling, and to investigate the impact of genomic alterations on therapeutic options and survival.Results: In our cohort of relapsed SCLC, the median number of genomic alterations was 5 (range, 1-11) per sample. The majority of patients were defined as low tumor mutation burden (TMB; 83.9%) and microsatellite stability (MSS; 87.1% ). Immune checkpoint inhibitors (ICIs)-based treatment still brought considerable progression-free survival (PFS; 4.93-20.27 months) for patients with low TMB and MSS. Additionally, the most frequent genetic alterations observed in relapsed SCLC were TP53 (77%) and RB1 (52%). Other genomic alterations of high frequency were breast cancer 2 (BRCA2) (32%), ataxia telangiectasia mutated (ATM) (13%), epidermal growth factor receptor (EGFR) (10%), Notch receptor 1 (NOTCH1) (10%), and Fanconi anemia complementation group A (FANCA) (10%), in turn. Finally, based on the survival of therapeutic strategies targeting potential mutation genes, the role of genotyping in relapsed SCLC was confirmed.Conclusions: Our studies first exhibited comprehensive genomic profiling of relapsed SCLC, identifying several candidate genes, and briefly analyzed the association of survival and genomic alterations. Our data from a small cohort of relapsed SCLC will benefit further exploration the potential targets or biomarkers.