Thymic epithelial tumors (TETs) are a relatively rare type of thoracic tumor, accounting for less than 1% of all tumors. The incidence of TETs is about 3.93/10000 in China, slightly higher than that of European and American countries. For resectable TETs, complete surgical resection is recommended. Radiotherapy or chemotherapy may be used as postoperative adjuvant treatment. Treatment for advanced, unresectable TETs consist mainly of radiotherapy and chemotherapy, but there is a lack of standard first‐ and second‐line treatment regimens. Recently, targeted therapies and immune checkpoint inhibitors have shown promising outcomes in TETs. Based on the currently available clinical evidences and the opinions of the national experts, the Thymic Oncology Group of Yangtze River Delta Lung Cancer Cooperation Group (East China LUng caNcer Group, ECLUNG; Youth Committee) established this Chinese expert consensus on the clinical diagnosis and treatment of TETs, covering the epidemiology, diagnosis, treatment, prognosis and follow‐up of TETs.

Anaplastic lymphoma kinase (ALK) rearrangement responds to ALK tyrosine kinase inhibitors (TKIs) in lung cancer. Many cases ultimately acquire resistance to crizotinib. Resistance, including ALK-dominant or ALK non-dominant, mechanisms have been described. Transformation to small-cell lung cancer is rare. Herein, we report a 49-year-old man diagnosed with adenocarcinoma, who was negative for EGFR and ALK genes as detected by reverse transcription polymerase chain reaction, and was treated with crizotinib. A new biopsy showed a small-cell lung cancer after disease progression. Then, next-generation sequencing (NGS) was carried out and detected a TP53 gene mutation, an ALK rearrangement, and no loss of the retinoblastoma gene (RB). Although a regimen for small-cell lung cancer may be one treatment option, a heterogeneous tumor may exist at the time of diagnosis and manifest during the course of disease.

De novo mesenchymal-to-epithelial transition (MET) gene fusions in non-small cell lung cancer (NSCLC) are a promising target for MET tyrosine kinase inhibitors (TKIs). We aimed to examine the response to targeted therapy with MET TKIs and resistance mechanisms in de novo MET fusion-positive NSCLC as these have not been comprehensively explored. We examined the MET fusions in 4,429 patients with advanced-stage NSCLC using targeted next-generation sequencing and validated the results using RT-PCR. We analyzed cellular models harboring MET fusions and established a patient-derived organoid (PDO) model. We identified 13 (0.29 %, 13/4429) patients with de novo MET fusions and found EPHB4, THAP5, TNPO3, and DST as novel MET fusion partners. The most common concomitant gene with MET fusions was TP53 mutations. Among 12 patients receiving MET TKI treatment, two achieved stable disease, six achieved partial response, and four underwent progressive disease. An in vitro study showed that EPHB4-MET is a functional driver gene. MET inhibitors significantly inhibited the proliferation and phosphorylation of downstream STAT3, AKT, and ERK1/2 in EPHB4-MET overexpressing cells. Acquired MET D1228H/N or D1246N mutations were found in patients harboring MET fusions after acquiring resistance to MET TKIs. Tivantinib showed optimal suppression efficacy in a PDO model with an acquired MET D1228N mutation. MET fusions occur in a rare subset of patients with NSCLC and represent a promising therapeutic target. MET secondary mutations D1228H/N or D1246N present the potential resistance mechanisms of MET inhibitors in patients with de novo MET fusions.

KRAS gene mutations are well known as a key driver of advanced non-small cell lung cancer (NSCLC). The impact of KRAS-mutant subtypes on the survival benefit from salvage chemotherapy is controversial. Here, we present a real-world study in patients across China with advanced NSCLC with KRAS mutations using a website-based patient self-report system. We identified a total of 75 patients diagnosed with KRAS-mutant (determined by molecular sequencing) advanced NSCLC between 2014/5/9 and 2019/5/30. KRAS mutation subtypes were divided into G12C and non-G12C groups for statistical analysis. The clinicopathological characteristics and treatment survival benefit in all patients with a KRAS mutation were evaluated. Programmed death-ligand 1 (PD-L1) expression data were collected from 30 patients in the same cohort. In this study, 23 patients with stage IIIB NSCLC and 52 patients with stage IV NSCLC were enrolled with 58 men and 17 women; the median age was 60 years (39-84). All patients received regular chemotherapy/radiotherapy/targeted therapy/immune therapy as per the disease condition. Four main KRAS mutation subtypes were detected: G12C (33%), G12V (19%), G12A (12%), and G12D (12%). Three predominant KRAS comutations were detected: TP53-KRAS (31%), EGFR-KRAS (11%), and STK11-KRAS (8%). Compared with the KRAS non-G12C mutation subtype, patients with the KRAS G12C mutation had potentially longer progression-free survival (PFS) after first-line chemotherapy (4.7 vs. 2.5 months, p < 0.05). Pemetrexed-based chemotherapy appeared to be superior to taxanes- and gemcitabine-based chemotherapies in all patients (PFS: 5.0 vs. 1.5 and 2.3 months, respectively, p > 0.05). Cox regression analysis showed that the KRAS G12C mutation and pemetrexed-based first-line chemotherapy were positive influencers for PFS after first-line (hazard ratios = 0.31 and 0.55, respectively, P < 0.05), but not second-line chemotherapies. The KRAS G12C mutation could be a predictive biomarker for better survival benefit from first-line chemotherapy in patients with advanced NSCLC and KRAS mutations. The first-line chemotherapy regimen could possibly influence the outcome in patients with KRAS mutations. Larger and prospective clinical trials are warranted to confirm our conclusions.

Y C Zhu, W X Wang, C W Xu, Q X Zhang, K Q Du, G Chen, T F Lv, Y Song; Identification of a novel crizotinib-sensitive MET-ATXN7L1 gene fusion variant in lung ad

MET amplification is associated with acquired resistance to first-generation epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) in treating non-small-cell lung cancer (NSCLC); however, the therapeutic strategy in these patients is undefined. Herein we report the clinical outcomes of patients with c-MET amplification resistance to EGFR-TKIs treated with crizotinib. We retrospectively analyzed advanced NSCLC patients from five sites who were diagnosed with EGFR-mutant NSCLC and received EGFR-TKI treatment. After disease progression, these patients were confirmed to have a MET-to-centromere ratio (MET:CEN) ≥ 1.8 based on fluorescence in situ hybridization (FISH) examination and without a T790M mutation. We assessed the efficacy and safety of crizotinib to overcome EGFR-TKI resistance in EGFR-activating mutations NSCLC with acquired MET amplification. Amplification of the acquired MET gene was identified in 18 patients with EGFR-mutant NSCLC. Fourteen patients received crizotinib treatment after acquired resistance to EGFR-TKIs. Among the 14 patients, 6 (42.9%) received crizotinib plus EGFR-TKI and 8 (57.1%) received crizotinib monotherapy. The overall objective response rate (ORR) and disease control rate (DCR) were 50.0% (7/14) and 85.7% (12/14), respectively. The median PFS (mPFS) of patients receiving crizotinib monotherapy and crizotinib plus EGFR-TKI was 6.0 and 12.6 months, respectively (P = 0.315). Notably, treatment efficacy was more pronounced in patients with crizotinib than patients with chemotherapy (24.0 months vs. 12.0 months, P = 0.046). The mOS for 8 of 14 patients receiving crizotinib monotherapy and 6 of 14 patients receiving crizotinib plus EGFR-TKI was 17.2 and 24.0 months, respectively (P = 0.862). Among the 14 patients, 1 who received crizotinib monotherapy (grade 3 nausea) and 2 who received crizotinib plus EGFR-TKI (grade 3 elevated liver aminotransferase levels) received reduced doses of crizotinib (200 mg twice daily) to better tolerate the dose. We observed the clinical evidence of efficacy generated by combination of crizotinib and previous EGFR-TKIs after the resistance to first-generation EGFR-TKIs. These results might increase evidence of more effective therapeutic strategies for NSCLC treatment. Combination therapy did not increase the frequency of adverse reactions.