Myositis - A common but underreported adverse effect of osimertinib: Case series and review of the literature

Serum creatine kinase elevation following tyrosine kinase inhibitor treatment in cancer patients: Symptoms, mechanism, and clinical management

Molecular targeted tyrosine kinase inhibitors (TKIs) have produced unprecedented treatment response in cancer therapy for patients harboring specific oncogenic mutations. While the TKIs are mostly well tolerated, they were reported to increase serum levels of creatine kinase (CK) and cause muscle metabolism-related toxicity. CK is an essential enzyme involved in cellular energy metabolism and muscle function. Elevated serum CK levels can arise from both physiological and pathological factors, as well as triggered by specific drug classes. The incidence of serum CK elevation induced by a few approved TKIs (brigatinib, binimetinib, cobimetinib-vemurafenib combination [Food and Drug Administration, United States]; aumolertinib, and sunvozertinib [only approved by National Medical Products Administration, China]) were over 35%. CK elevation-related symptoms include myopathy, myositis, inclusion body myositis (IBM), cardiotoxicity, rhabdomyolysis, rash, and acneiform dermatitis. High-level or severe symptomatic CK elevation may necessitate dose reduction and indirectly dampen TKI efficacy. This review presents an updated summary about the prevalence rate and recent research about mechanisms leading to TKI-induced serum CK elevation in cancer patients. The utility of monitoring serum CK levels for predicting TKI-induced adverse effects and their management will also be discussed.

Osimertinib-Induced Myositis in a Patient With Metastatic Non-small Cell Lung Cancer With Epidermal Growth Factor Receptor Mutation

Osimertinib is a third-generation tyrosine kinase inhibitor (TKI) that has emerged as a standard treatment in non-small cell lung cancer (NSCLC) with epidermal growth factor receptor (EGFR) mutation. While it is generally well tolerated, milder side effects of diarrhea, cytopenia, and cutaneous rashes are common. Osimertinib-induced myositis and rhabdomyolysis are exceedingly rare, and only a few cases have been documented in the literature to date. In this report, we present a case of a 59-year-old female with metastatic NSCLC who experienced myalgia following the initiation of osimertinib. Blood work revealed elevated creatine kinase (CK), serum creatinine (Cr), alanine aminotransferase (ALT), and aspartate aminotransferase (AST). Initially, her myalgia improved, and lab work normalized after drug discontinuation and supportive care. However, rechallenge with a 50% dose resulted in recurrence of symptoms and elevated serum CK, Cr, ALT, and AST. MRI findings suggested diffuse inflammation and a muscle biopsy revealed necrotizing myopathy. Symptoms ameliorated upon complete cessation of the drug and use of steroids. This case highlights the importance of recognizing this rare adverse effect of osimertinib and a guide for managing these associated symptoms.

Gefitinib-induced Myositis: A Novel Case Report

Chemotherapy-induced myositis is a severe adverse event caused by chemotherapeutic agents such as immune checkpoint inhibitors (ICIs) or cytotoxic agents. We experienced a patient with gefitinib-induced myositis with symptoms of muscle cramps and stiffness in the limbs, and reported the treatment process. A 70-year-old woman received four courses of carboplatin (CBDCA)+pemetrexed (PEM)+gefitinib (intravenous CBDCA area under the curve (AUC) 5 and PEM 500 mg/m2, every 3 weeks, and oral gefitinib 250 mg daily), for epidermal growth factor receptor (EGFR) mutation-positive stage IV lung cancer treatment; followed by seven courses of PEM+gefitinib, and continued gefitinib monotherapy thereafter. Myositis occurred 5 months after the initiation of gefitinib monotherapy. She developed strong limb cramps despite regular oral administration of 400 mg acetaminophen three times a day and complained of pain on a numeric rating scale of 10/10. Her creatine kinase (CK) was elevated from the second course of CBDCA+PEM+gefitinib but was stable at grade 1-2 thereafter. However, the muscle symptoms disappeared with CK normalization within a few days of gefitinib discontinuation due to disease progression. The Naranjo Adverse Drug Reaction Scale score was 6, suggesting a probable association. Osimertinib (an EGFR tyrosine kinase inhibitor)-induced myositis has been reported, but similar events were first observed with gefitinib in this case. Consequently, when treating with gefitinib, myositis, including the CK variation, should be monitored and appropriately managed with multidirectional treatment.

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

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.

Elevated serum creatine kinase levels due to osimertinib: A case report and review of the literature

INTRODUCTION

Osimertinib is a tyrosine kinase inhibitor that targets the epidermal growth factor receptor. Elevated serum creatine kinase level is an uncommon adverse event associated with osimertinib treatment for lung cancer.

CASE REPORT

We report a previously healthy 56-year-old woman who developed elevated serum creatine kinase levels during osimertinib monotherapy for epidermal growth factor receptor mutation-positive lung adenocarcinoma.

MANAGEMENT & OUTCOME

During treatment, she experienced leg cramps and her serum creatine kinase levels increased, peaking at 989 U/l. Further investigation revealed no evidence of cardiotoxicity or myositis; thus, osimertinib-induced myopathy was assumed to be the cause of her elevated serum creatine kinase levels. We successfully managed both lung cancer and osimertinib-induced myopathy using 1-week pauses of osimertinib therapy without dose reduction.

DISCUSSION

Short-term suspension of osimertinib without dose reduction may be a reasonable option for osimertinib-induced myopathy.