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Background: Several patients treated with osimertinib experience progressive disease. The aim was to clarify the mechanisms underlying resistance to osimertinib., Methods: ELUCIDATOR: A multi-centre, prospective, observational study involved chemotherapy-naive patients with advanced non-small cell lung cancer receiving osimertinib. Mutations in cancer-associated genes, detected via ultrasensitive next-generation sequencing of circulating tumour deoxyribonucleic acid samples, were collected at baseline and after progressive disease detection. These paired plasma samples were compared., Results: Of 188 patients enrolled (May 2019-January 2021), 178 (119 females [67 %]) median age 74 years, were included. Patients, n = 95 (53 %) had epidermal growth factor receptor exon 19 deletion mutations. Among 115 patients with progressive disease, circulating tumour deoxyribonucleic acid levels of 85 patients were analysed. MET amplification (n = 4), TP53 mutations (n = 4), PIK3CA mutations (n = 3), BRINP3 mutation (n = 2), BRAF mutation (n = 2), APC mutation (n = 1), RET mutation (n = 1) and epidermal growth factor receptor (EGFR) resistance mutation, and C797S (n = 1) were detected. Patients with baseline TP53 mutations, with MET or EGFR amplification had shorter progression-free (PFS) and overall survival. Patients with PIK3CA mutations tended to shorter PFS., Conclusion: MET amplification and PIK3CA mutation mechanisms underly resistance to osimertinib in patients. Patients with coexisting mutations or amplifications at baseline had shorter PFS and overall survival., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

The natural history of lung adenocarcinoma with ground-glass opacity (GGO) remains undetermined. We describe a lung adenocarcinoma in which GGO transformed through a scar-like lesion over the long term into a solid nodule of poorly differentiated adenocarcinoma. Whether poorly differentiated lung adenocarcinoma can evolve from GGO-type adenocarcinoma is an important issue that requires clarification.

It has been proposed that stepwise progression occurs from atypical adenomatous hyperplasia (AAH) through bronchioloalveolar carcinoma (BAC) to invasive lung adenocarcinoma. However, the underlying molecular mechanisms have not been identified. We report a patient with a mixed adenocarcinoma of the lung that had different EGFR mutations in the papillary subtype, the acinar subtype, and the surrounding AAH and BAC areas. EGFR mutations may accumulate during tumor progression and lead to heterogeneity of EGFR mutations within the tumor.

Gefitinib, a tyrosine kinase inhibitor of epidermal growth factor receptor (EGFR), produces radiographic regression and symptom relief in patients with refractory advanced non-small cell lung cancer. However, it remains controversial whether gefitinib improves patient survival. We report three cases of refractory metastatic non-small cell lung cancer who have survived approximately 3 years since they first started gefitinib. These long-term survivors were Japanese female non-smokers with adenocarcinoma, who often had multiple lung metastases and were effectively re-treated with gefitinib. One patient had a surgical specimen available for DNA extraction and showed deletions in exon 19 of EGFR. Our experience suggests that gefitinib may improve long-term survival in selected patients. Further studies are required to identify biomarkers downstream of the EGFR mutations that are involved in multiple lung metastases and which could identify those patients who may benefit from gefitinib re-treatment.