Osimertinib, a third-generation EGFR tyrosine kinase inhibitor, is the standard of care for patients with advanced NSCLC and EGFR-sensitizing mutations. Both in osimertinib pivotal trials and in the post-marketing phase, asymptomatic creatinine phosphokinase elevation and clinically relevant muscle damage have been reported. However, the mechanisms underlying these conditions remain unclear. Herein, we report the first muscle biopsy description of osimertinib-induced myopathy and hypothesize that the mechanisms underpinning muscle toxicity could be driven by hyporegenerative mechanisms and mitochondrial dysfunction with subsequent reduced metabolic endurance, both directly linked to the inhibition of downstream molecular pathways mediated by EGFR in muscle cells.

Osimertinib administration has been approved as an adjuvant treatment after complete surgical resection in patients with EGFR-mutated NSCLC. This article presents the first report of life-threatening postoperative osimertinib-induced interstitial lung disease. An 83-year-old male patient underwent right upper lobectomy (pathologic stage IIA) and osimertinib (80 mg/d) was initiated on postoperative day 75. On day 44 of osimertinib administration, chest computed tomography revealed diffuse ground-glass opacities; accordingly, osimertinib-induced interstitial lung disease was diagnosed. Steroid pulse therapy was initiated using a high-flow nasal cannula to treat dyspnea and hypoxemia, rapidly improving the respiratory status and imaging findings; moreover, the patient\'s clinical course was excellent. This case report suggests that the postoperative occurrence of severe osimertinib-induced interstitial lung disease is a crucial factor that must be considered in patient decision-making regarding perioperative treatment.

Background: The treatment paradigm for advanced non-small-cell lung cancer (NSCLC) is rapidly changing. Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) and anti-programmed death-1 (PD-1) antibodies have increasingly been incorporated into routine care for nearly all patients with NSCLC. Toripalimab was recently approved as the first-line treatment for advanced non-squamous NSCLC in combination with chemotherapy. Stevens-Johnson syndrome (SJS) is a rare but potentially fatal complication of TKI and anti-PD-1 therapy. We reported a case of SJS after sequential use of EGFR-TKIs and toripalimab in an NSCLC patient with EGFR mutations 19 del/T790M/C797S in trans and cis. Case presentation: A 58-year-old man with stage IV NSCLC received gefitinib because next-generation sequencing (NGS) revealed an EGFR 19del, followed by osimertinib and pemetrexed with the emergence of EGFR T790M. Four EGFR mutations 19 del/T790M/C797S in trans and cis were detected after osimertinib resistance. The combination of toripalimab and docetaxel was administered as a third-line treatment. The patient developed SJS at 21 days, and toripalimab was discontinued. After treatment with methylprednisolone and prednisolone, the skin toxicity of the patient gradually decreased and eventually disappeared. The patient received osimertinib and anlotinib after recovery, and SJS has not recurred. The ongoing treatment is still effective and results in stable disease. Conclusion: We reported the first case of SJS induced by toripalimab in a patient with lung adenocarcinoma harboring multiple EGFR mutations. The TKI treatment after SJS was well tolerated and effective.

Erlotinib is an oral and reversible epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor and is now used exclusively to non-small cell lung carcinoma (NSCLC) harboring mutated EGFR. However, there was historically a transient period when erlotinib was widely used regardless of EGFR mutation status. We report two cases with adenocarcinoma and wild-type EGFR status, which responded to erlotinib for unusual long time. We also retrospectively analyzed patients with adenocarcinoma and wild-type EGFR mutation status who had received erlotinib-containing regimen in our hospital. A 60-year-old woman received the second-line and tri-weekly regimen of pemetrexed (500 mg/m2 on day 1) and intermittent erlotinib (150 mg on days 2 - 16). Pemetexed was discontinued 18 months after the initiation of this regimen, but erlotinib was continued for more than 11 years. This chemotherapy successfully reduced her brain metastasis and prevented recurrence. A 58-year-old man received erlotinib monotherapy as the third-line regimen, by which multiple brain metastases disappeared. Although we tried stopping erlotinib 9 years after the initiation of erlotinib, a solitary metastasis appeared in the brain 3 months after the discontinuation of erlotinib. Between December 2007 and October 2015, 39 patients with wild-type EGFR status initiated erlotinib-containing regimens at our hospital. The response rate, progression-free survival and overall survival were 17.9% (95% confidence interval (CI): 7.5-33.5%), 2.7 months (95% CI: 1.8 - 5.0 months) and 10.3 months (95% CI: 5.0 - 15.7 months), respectively. We reported two long-term responders and survivors to erlotinib for more than 9 years, which was much longer than patients with adenocarcinoma and wild-type EGFR mutation status who had received erlotinib-containing regimen in our hospital.

In the non-small-cell lung cancer (NSCLC) subtype, adenocarcinoma is the most common histology. The choice of first-line treatment depends on the mutational status. We present a case of a 54-year-old non-smoker woman with lung adenocarcinoma and extensive metastatic disease at diagnosis. The genetic analysis demonstrated a sensitizing epidermal growth factor receptor (EGFR) exon 19 mutation and she began treatment with a first-generation EGFR tyrosine kinase inhibitor (TKI), erlotinib. Due to successively acquired resistances and disease progression, six treatment lines were pursued, including third-generation EGFR TKI and chemotherapy. The patient accomplished an overall survival of 47 months. This case emphasized the importance of monitoring tumor mutational alterations, allowing us to implement a multi-line treatment. Targeted therapy in advanced NSCLC largely improved the overall survival of these patients.

Epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) are currently considered as the standard therapy for patients with advanced non-small cell lung cancer (NSCLC) who have EGFR-activating mutations. However, despite an initially profound response to these drugs, these patients ultimately develop drug resistance. The most common resistance mechanism is the development of a secondary mutation in EGFR (T790M), although activation of the MNNG/HOS transforming gene (MET), amplification of the Erb-B2 receptor tyrosine kinase 2 gene and histological transformation to small cell lung cancer may also lead to resistance. In addition, there may be additional, rare mechanisms leading to resistance that remain unidentified. Mutations in the EGFR kinase domain duplication (EGFR-KDD) are rare, although they act as oncogenic drivers in NSCLC. To the best of our knowledge, all studies to date have reported EGFR-KDD as the primary mutation in NSCLC. The aim of the present study was to report the case of an EGFR-KDD mutation in a patient with NSCLC who developed acquired resistance to gefitinib, but responded well to afatinib. Therefore, EGFR-KDD mutation is an additional potential mechanism underlying the development of acquired resistance to EGFR-TKIs.

BACKGROUND: Gastric cancer is the fifth most diagnosed cancer worldwide and the third most common cause of cancer-related death. In recent decades, increasing application of next-generation sequencing has enabled detection of molecular aberrations, including fusions. In cases where tissue is difficult to obtain, cell-free DNA (cfDNA) is used for detecting mutations to identify the molecular profile of cancer. Here, we report a rare case of EGFR-SEPT14 fusion detected from cfDNA analysis in a patient with gastric cancer.
METHODS: A 49-year-old female diagnosed with advanced gastric cancer in July 2019 received capecitabine and then combination chemotherapy of ramucirumab and paclitaxel, but ascites was detected. The therapy was switched to nivolumab, but disease progression was observed on a positron emission tomography/computed tomography scan in May 2020. Therapy was discontinued, and cfDNA next-generation sequencing was immediately evaluated. All genomic variants, including fusions, were analyzed from cfDNA. The following somatic alterations were detected from the patient\'s cfDNA: an APC frameshift mutation (NM_000038.5:c.6579del, p.V2194fs) with variant allele frequency of 0.5%, an EGFR amplification with a copy number of 17.3, and an EGFR-SEPT14 fusion with variant allele frequency of 45.3%. The site of the fusion was exon 24 of EGFR fused to exon 10 of SEPT14. The fusion was in-frame and considered to be protooncogenic. Although the patient refused to continue therapy, we suggest that EGFR-targeted therapies be tried in such future cases.
CONCLUSIONS: The expanded applications of the cfDNA assay may open a new horizon in treatment of patients with advanced gastric cancer.

Toxic epidermal necrolysis (TEN) and Stevens-Johnson syndrome (SJS) are life-threatening dermatologic adverse events in the same category, caused by a delayed-type drug hypersensitivity reaction. Although skin toxicity is common during treatment with epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs), osimertinib-associated TEN is quite rare-thus far, only one report has been published from China. We report a case of an 80-year-old Japanese woman with lung adenocarcinoma harboring an EGFR-sensitizing mutation who was treated with osimertinib as the first-line treatment. Forty-six days after osimertinib induction, diffuse erythematous rash rapidly spread over the patient\'s trunk along with vesicles and purpuric macules; furthermore, she developed targetoid erythema on the face. Despite osimertinib discontinuation and corticosteroid treatment, diffuse erythema with Nikolsky\'s sign, general epidermal detachment, erosion and loose blisters developed over her entire body including the face. Based on her symptoms, TEN was diagnosed and thus, intravenous immunoglobulin was immediately administered for 4 days. The treatment ameliorated TEN-associated skin toxicity and caused epithelialization. Reports on osimertinib-associated SJS/TEN are scarce and only one report each on SJS and TEN from China is available. This is the first report of osimertinib-associated TEN from Japan. Cases of EGFR-TKI-associated SJS/TEN have been reported predominantly from Asian countries, suggesting ethnicity and genetic linkage play a role in the underlying mechanism.