In China, gastric cancer is the second most common cause of cancer-related death, after lung cancer. At present, the morbidity and mortality rates of gastric cancer are increasing, and targeted therapy for gastric cancer has become a research hotspot. Herein, we report a patient with multiple metastases from advanced gastric cancer. After identifying MET gene amplification, initial treatment induced regression of the tumor. However, in later stages, due to the overexpression or mutation of HER-2, KRAS, TP53, and other genes, the targeted drug therapy became ineffective, and the disease progressed rapidly, leading to the death of the patient.

UNASSIGNED: Cholangiocarcinoma (CCA) is an aggressive disease with limited treatment options. Despite substantial efforts to explore better regimens, gemcitabine-based chemotherapy has been the standard first-line treatment for decades. With the growing field of precision medicine, biomarker-guided treatments are gaining popularity. MET alteration is a frequent occurrence in various cancer types, making it a promising target.
UNASSIGNED: A 53-year-old man visited our hospital with a complaint of upper abdominal pain. Advanced CCA was diagnosed based on the biopsy of the metastatic lymph nodes and immunohistochemistry. Next-generation sequencing revealed MET amplification. As the patient was intolerant to traditional chemotherapy, savolitinib (a c-MET inhibitor) was administered. Partial response was achieved, and the treatment was well tolerated. After 1 year, the patient developed progressive disease, to which the emergence of epidermal growth factor receptor amplification may have contributed.
UNASSIGNED: Our study verified the therapeutic value of a c-MET inhibitor in advanced CCA-harboring MET amplification and provides an alternative strategy for patients who are intolerant to chemotherapy.

RET fusions occur in 1-2% of non-small cell lung cancer. Selpercatinib and pralsetinib are selective RET inhibitors with significant improvement of outcome in patients with tumor harboring RET fusion; however, resistance mechanisms appear frequently, mainly driven by MAPK pathway bypass, secondary RET mutations, or in 5% via MET amplification. Co-inhibition of RET and MET is a compelling strategy for overcoming MET-dependent resistance to RET inhibitors and potentially other inhibitors. To our knowledge, this is the first report of a novel ISOC1-RET fusion lung cancer with a durable complete response to selpercatinib, with resistance via MET amplification, which was overcome by the successful combination of selpercatinib and capmatinib.

Preclinical cases suggest that EGFR tyrosine kinase inhibitors (TKIs) plus MET TKIs are a potential therapy for non-classical EGFR mutant lung cancers with MET amplification acquired resistance. Herein, we report for the first time the effectiveness of novel combination treatment regimens for patients with EGFR G719X/S768I/L861Q. Until the last follow-up assessment, two patients demonstrated improved survival after they switched to afatinib combined with savolitinib (PFS: 10 months) and furmonertinib combined with crizotinib (PFS: 6 months), respectively, that did not observed increased incidence and severity of adverse events. According to the findings of this study and literature review, various responses were observed from the combined therapy in NSCLC patients who harbored uncommon EGFR mutations and MET amplification. Furthermore, Next generation sequencing (NGS) leads to the discovery of uncommon of EGFR and reveals the co-mutations in NSCLC.

Non-small-cell lung cancer (NSCLC) is the most common cancer in the world. In recent years, the incidence of synchronous multiple primary lung cancer (SMPLC) has gradually increased. Surgery is the preferred method to treat these patients. The management of SMPLC patients who cannot tolerate surgical treatment is controversial. We report a rare case in which a 70-year-old Chinese woman with no history of smoking had three primary lung adenocarcinoma lesions. Two lesions had epidermal growth factor receptor (EGFR) exon 19 deletion mutations, and one lesion had the L858R mutation. After first-generation EGFR-tyrosine kinase inhibitor (TKI) treatment, the three lesions all showed a good response until disease progression. After the corresponding drug treatments were given based on the different drug resistance mechanisms, good responsiveness was shown in each lessions. This case suggests that in the treatment of SMPLC, it is necessary to learn the molecular-biological information of each lesion due to the differences thereof, and a targeted treatment regimen should be developed on this basis.

Gallbladder cancer (GBC) is a highly invasive disease and the most prevalent malignancy of the biliary system. Patients with GBC are commonly diagnosed at a late stage and have an unfavorable prognosis. Palliative chemotherapy has been the standard care for recurrent or metastatic disease in the past decades. Recently, several targeted therapies have been investigated in advanced biliary tract cancer (BTC) including inhibitors of genes or pathways such as FGFR2 fusions or rearrangements, IDH1 mutations, and NTRK gene fusions. Also, several clinical studies involving molecular stratification have been performed in defined patient groups, for example, BRAF V600E and HER2. Mesenchymal epithelial transition(MET)encodes a tyrosine kinase receptor and its ligand hepatocyte growth factor is a proto-oncogene. Targeting the MET signaling pathway is an effective strategy in numerous cancer types. However, the poor efficacy of MET inhibitors has been demonstrated in several phase II studies, but currently no reports have explained the potential mechanisms of resistance to MET inhibitors in BTC. In this article, we report a case of metastatic GBC with MET amplification that exhibited a rapid response to crizotinib after the failure of two lines of chemotherapy. After the patient had progressed and discontinued crizotinib, cabozantinib was introduced. Analysis of circulating tumor DNA (ctDNA) by next-generation sequencing (NGS) indicated a loss of MET amplification status. To our knowledge, this is the first case study demonstrating the use of NGS in ctDNA to monitor the development of acquired resistance during anti-MET treatment in GBC.

The acquired resistance of epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) is inevitable and heterogeneous. The strategies to overcome acquired resistance are significant. For patients with secondary T790M-positive after early generation EGFR-TKIs, osimertinib is the standard second-line therapy. In patients resistant to prior early generation EGFR-TKIs, the acquired T790M mutation overlaps with other driver gene resistance, such as HER2-and MET amplification, accounting for 4-8%. The efficacy of osimertinib is unclear in patients with concurrent multiple driver gene resistance. We here report a patient who acquired EGFR T790M, STRN-ALK fusion, and EGFR amplification after gefitinib progression and subsequent MET amplification acquired from osimertinib. The other patient acquired EGFR T790M and MET amplification post-dacomitinib and acquired CCDC6-RET fusion after osimertinib treatment. Besides, subsequent new bypass activations were the possible resistance mechanisms to second-line osimertinib. Both patients had progression-free survival (PFS) less than 4 months and limited benefits from osimertinib second-line therapy. The T790M accompanying driver gene resistance will be a new subtype after EGFR-TKIs progression, needing effective treatment options.

BRAF fusions are rare driver oncogenes in non-small cell lung cancer (NSCLC). Similar with BRAF V600E mutation, it could also activate the MAPK signaling pathway. There are a few case reports which had indicated the potential response to BRAF inhibitors and its important role as de novo driver mutation. In addition, the co-occurring MET amplification has been defined as a poor prognostic factor in patients with epidermal growth factor receptor (EGFR) mutant NSCLC. Currently, there are ongoing clinical trials which investigate the MET amplification as a therapeutic target in patients with EGFR mutant NSCLC and acquired resistance to osimertinib, which imply that the MET amplification also had a therapeutic significance. However, the co-occurring MET amplification had not been studied in patients with BRAF fusion before. A 67-year-old man was diagnosed with metastatic poorly-differentiated adenocarcinoma. He received first-line therapy with the combination of pembrolizumab and chemotherapy because the genomic test revealed wild-type EGFR, and negativity of ALK and ROS1 by immunohistochemical stain. Upon disease progression, the next-generation sequencing revealed co-occurring KIAA1549-BRAF fusion and MET amplification. Subsequent dabrafenib, trametinib, and capmatinib combination therapy showed a remarkable treatment effect. The combination therapy targeting the co-occurring driver mutations is a potential effective treatment for NSCLC patients. Further prospective study is still warranted to investigate the role of co-occurring driver mutations and the relevant treatment strategy.

Cholangiocarcinoma is a highly morbid gastrointestinal malignancy for which available therapies are limited. Standard of care includes cytotoxic chemotherapies such as gemcitabine, platinum agents, nab-paclitaxel, and fluoropyrimidine analogues. However, tolerability of these regimens varies, and patients who do not tolerate chemotherapy have limited targeted therapies and immunotherapy options. In cholangiocarcinoma, mesenchymal-epithelial transition factor (MET) amplification may present an additional opportunity for a targeted therapeutic approach, especially considering emerging data in non-small cell lung cancer. In this case, we present a metastatic cholangiocarcinoma patient with high-level MET gene amplification for whom capmatinib, a tyrosine kinase inhibitor with activity against c-MET, provided a partial response after cessation of chemotherapy.

Anaplastic lymphoma kinase tyrosine kinase inhibitors (ALK-TKIs) have been found to significantly improve the quality of life and survival in ALK-positive non-small cell lung cancer (NSCLC) patients. However, the duration of responses is limited by drug resistance. Genetic heterogeneity of ALK-positive tumors could potentially explain the differences in individual patient outcomes. We performed next-generation sequencing (NGS) on plasma samples, pleural effusion samples, and tissue re-biopsy obtained at various treatment milestones from an ALK rearrangement lung adenocarcinoma patient undergoing targeted therapy. The liver metastases of the EML4-ALK NSCLC patient presented rapid progression after 3.5 months of alectinib, while the other lesions showed good partial response. Targeted NGS identified the newly emerged MET amplification except for EML4-ALK in plasma ctDNA and liver lesions. Subsequently, a clinical benefit was achieved one month after the commencement of crizotinib, a dual ALK and MET inhibitor; however, the patient experienced disease progression another month later. Several rounds of ALK-TKI combination therapy were tried but failed. Concurrent genetic alterations, including loss-of-function mutations in FBXW7 and MLL3, may mainly contribute to poor prognosis in the patient. It highlighted the molecular profiling by using NGS can be useful in identifying the heterogeneity across lesions and the resistance mechanism of targeted treatments.