Life-Threatening Myositis in a Patient With EGFR-Mutated NSCLC on Osimertinib: Case Report

Abstract

Osimertinib is the standard of care for the first-line treatment of EGFR -mutated NSCLC. We report a case of a 52-year-old woman who developed life-threatening myopathy because of treatment with osimertinib. Limited instances of myositis have been previously reported in the literature; however, none have resulted in life-threatening oropharyngeal and respiratory muscle weakness as seen in this case. Care should be taken in administering osimertinib concurrently with other medications metabolized by the CYP3A4 system, and ongoing work to identify patients at risk for severe reactions is necessary. The use of routine creatinine phosphokinase monitoring should be considered as part of oncologic management.

Gefitinib-induced Myositis: A Novel Case Report

“…Atorvastatin is weak inhibitor of CYP3A4, 17) therefore gefitinib metabolism may have been delayed, resulting in the symptom development of symptoms. A similar process was confirmed in previous reports regarding osimertinib-induced symptoms, [5][6][7] suggesting that elevated CK may be a predictor of myositis. Shusei et al reported a case of CK elevation without any symptoms 10 d after osimertinib initiation, with stabilization at approximately 600 U/L.…”

“…12) Although EGFR-TKI-induced myositis is uncommon, it has recently been reported with osimertinib. [5][6][7] We speculate that EGFR-TKI-induced myositis The patient had taken 10 mg of atorvastatin before gefitinib initiation. CK elevated on day 47.…”

“…Fionnuala et al reported a severe case in which the patient was unable to walk without assistance due to muscle soreness and weakness 12 d after osimertinib initiation, with CK elevation to 29680 U/L and liver dysfunction. 7) Osimertinib was discontinued, and pulse-dose steroids and immunoglobulins were administered to treat the symptoms. These reports indicate that myositis appears within a range of a few days to several months.…”

“…Chemotherapy-induced myositis is a severe adverse event caused by chemotherapeutic agents such as immune checkpoint inhibitors (ICIs), cytotoxic agents, molecular target agents; gemcitabine, docetaxel, sunitinib, and osimertinib. [1][2][3][4][5][6][7] Gefitinib is an epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) that has been shown to significantly prolong progression-free survival (PFS) in advanced non-small cell lung cancer with EGFR mutation. 8) Although it is no longer the first-choice drug, it is sometimes used as monotherapy or in combination with cytotoxic agents when osimertinib is not available.…”

“…[9][10][11] EGFR-TKIinduced myositis is uncommon, but has been reported with osimertinib treatment. [5][6][7] We experienced a case of gefitinib-induced myositis with symptoms of muscle cramps and stiffness in limbs with elevated creatinine kinase (CK) levels and report the treatment process below.…”