MET alterations, including MET exon 14 skipping variants, MET amplification, MET overexpression, and MET fusion, play pivotal roles in primary tumorigenesis and acquired resistance to targeted therapies, especially EGFR tyrosine kinase inhibitors. They represent important diagnostic, prognostic, and predictive biomarkers in many solid tumor types. However, the detection of MET alterations is challenging due to the complexity of MET alterations and the diversity of platform technologies. Therefore, techniques with high sensitivity, specificity, and reliable molecular detection accuracy are needed to overcome such hindrances and aid in biomarker-guided therapies. The current review emphasizes the role of MET alterations as oncogenic drivers in a variety of cancers and their involvement in the development of resistance to targeted therapies. Moreover, our review provides an overview of and recommendations on the selection of various cross-platform technologies for the detection of MET exon 14 skipping variants, MET amplification, MET overexpression, and MET fusion. Furthermore, challenges and hurdles underlying these common detection platforms are discussed.

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.

Utilizing targeted therapy against activating mutations has opened a new era of treatment paradigms for patients with advanced non-small cell lung cancer (NSCLC). For patients with epidermal growth factor (EGFR)-mutated cancers, EGFR inhibitors, including the third-generation tyrosine kinase inhibitor (TKI) osimertinib, significantly prolong progression-free survival and overall survival, and are the current standard of care. However, progression after EGFR inhibition invariably occurs, and further study has helped elucidate mechanisms of resistance. Abnormalities in the mesenchymal-epithelial transition (MET) oncogenic pathway have been implicated as common alterations after progression, with MET amplification as one of the most frequent mechanisms. Multiple drugs with inhibitory activity against MET, including TKIs, antibodies, and antibody-drug conjugates, have been developed and studied in advanced NSCLC. Combining MET and EGFR is a promising treatment strategy for patients found to have a MET-driven resistance mechanism. Combination TKI therapy and EGFR-MET bispecific antibodies have shown promising anti-tumor activity in early clinical trials. Future study including ongoing large-scale trials of combination EGFR-MET inhibition will help clarify if targeting this mechanism behind EGFR resistance will have meaningful clinical benefit for patients with advanced EGFR-mutated NSCLC.

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.

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.

Paraneoplastic eosinophilia is a rare complication observed in 1% solid tumor cases and appears to have tumor type-dependent prognostic impact, in which the increased eosinophil count was generally associated with unfavorable prognosis. In the English literature, more than 20 patients have been reported of eosinophilia associated with primary non-small cell lung cancer (NSCLC) at diagnosis, all of whom underwent either surgery, chemotherapy, or symptomatic therapy. Herein, we describe clinical course a stage IV NSCLC patient with paraneoplastic eosinophilia and leukocytosis and receiving targeted therapy. A 64-year-old male former smoker was diagnosed with lung adenocarcinoma harboring EGFR L858R mutation and MET amplification. Blood eosinophilia was manifested at diagnosis and confirmed to be paraneoplastic by eliminating other potential causes. The disease progressed rapidly within a month on EGFR inhibitor icotinib and then within three months on icotinib plus crizotinib after rapid response within the first month. A multi-target kinase inhibitor anlotinib was added, and the disease progressed one month later despite initial self-reported asymptomatic high-performance status. The patient was lost to subsequent follow-ups. Radiographic evaluation of disease control or progression coincided with respective distinct alleviation or worsening of eosinophilia. Consistent with previous reports of poor clinical outcome associated with blood eosinophilia, our results suggested a negative prognostic impact in EGFR-/MET-altered NSCLC. This case is, to the best of our knowledge, the first to provide evidence for blood eosinophilia paralleling disease progression in an EGFR- and MET-altered lung adenocarcinoma under targeted therapy, which suggested negative prognostic impact of blood eosinophilia in driver-positive NSCLC.