Efficacy of Intrathecal Pemetrexed Combined With Tyrosine Kinase Inhibitor for Treating Leptomeningeal Metastasis in EGFR-Mutant NSCLC After Failure of Osimertinib
Leptomeningeal metastasis (LM) is a complication of advanced non-small cell lung cancer (NSCLC). The incidence of LM in NSCLC patients is around 3-5 %, reaching 9.4 % of those with an epidermal growth factor receptor (EGFR) mutation. Generally, the efficacy of systemic treatment for LM is limited due to the blood-brain barrier. Osimertinib has a high central nervous system penetration rate, making it the preferred first-line treatment for EGFR-mutant NSCLC. Previous studies indicated that osimertinib had shown promising efficacy in pretreated patients harboring EGFR mutations and LM. However, intracranial disease progression eventually develops, and the prognosis of patients with LM progression after osimertinib is poor. Recently, intrathecal chemotherapy with pemetrexed (IP) was reported to be an alternative treatment in patients with NSCLC and LM. The results from a phase I/II trial examining the efficacy and safety of IP in patients with EGFR-mutant NSCLC after the failure of previous TKI, and 83% of study enrollees received osimertinib before IP. The clinical response rate was 84.6%, and the median overall survival was 9.0 months. Despite initial promising efficacy, further trials are needed to verify these results. Therefore, the investigators plan to conduct a prospective study to examine the safety and effectiveness of IP combined with EGFR-TKI for patients with EGFR mutant NSCLC after osimertinib failure.
• At least 20 years of age.
• Patients with metastatic non-squamous NSCLC harboring known EGFR activating mutation and with a diagnosis of probable or confirmed LM by the European Association of Neuro-Oncology-European Society for Medical Oncology (EANO-ESMO) guideline. \[5\] EGFR activating mutations include exon19 deletion, T790M, L858R, G719X, L861Q, or S768I.
• Intracranial disease progression after osimertinib use, proved by contrast-enhanced MRI
• Stable extra-cranial disease status, judged by investigators.
• Eastern Cooperative Oncology Group (ECOG) performance status 0-3 and a minimum life expectancy of 12 weeks
• Normal bone marrow and organ function as defined below:
‣ Marrow: Hemoglobin ≥9gm/dL, ANC ≥1500/mm3 platelets ≥100,000/mm3
⁃ Hepatic: Serum total bilirubin ≤1.5 x upper limit of normal (ULN), ALT (SGPT) and AST (SGOT) ≤3 x ULN.
⁃ Renal: Creatinine clearance (Ccr) ≥45 mL/min.
• For female patients of childbearing potential, agreement (by patient and/or partner) to use a highly effective form(s) of contraception that results in a low failure rate (\< 1% per year) when used consistently and correctly, and to continue its use for 5 months after the last dose of IP. Such methods include: combined (estrogen and progestogen containing) hormonal contraception, progestogen-only hormonal contraception associated with inhibition of ovulation together with another additional barrier method always containing a spermicide, intrauterine device (IUD), intrauterine hormone-releasing system (IUS), bilateral tubal occlusion, vasectomized partner (on the understanding that this is the only one partner during the whole study duration), and sexual abstinence.
• Ability to understand and willingness to sign an IRB approved written informed consent document.
• Willing to provide CSF and plasma samples for ctDNA analysis.