Pemetrexed is one of the first-line chemotherapeutic agents for non-squamous non-small cell lung cancer (NSCLC). Since 2017, intrathecal pemetrexed has shown good efficacy for patients with leptomeningeal metastases from NSCLC. It has been recommended as the preferred drug for intrathecal chemotherapy by the Chinese Society of Clinical Oncology (CSCO) guidelines. Tyrosine kinase inhibitors (TKIs) play a promising role in treating non-small cell lung cancer patients with epidermal growth factor receptor (EGFR) mutations. An international multi-center clinical study published in 2019 confirmed that double dose of osimertinib showed significant improvement in leptomeningeal metastases from NSCLC with EGFR exon 19 deletion or exon 21 L858R/T790M mutation. It makes TKIs the mainstay of treatment for patients with EGFR-mutant NSCLC with leptomeningeal metastases. However, the choice of treatment after resistance to targeted therapy is a hot topic in clinical practice, with 78% of patients in the study above who responded to double-dose osimertinib still showing progression at the time of follow-up. The purpose of this study was to observe the safety and efficacy of intrathecal pemetrexed for leptomeningeal metastasis from lung adenocarcinoma that progressed after a double dose of a third-generation TKI such as osimertinib.
Male or female aged between 18 and 75 years.
Histologically or cytologically confirmed diagnosis of NSCLC with single activating EGFR mutations (L858R or Exon19Del).
Confirmed diagnosis of leptomeningeal metastasis according to ESMO/ EANO guidelines.
Progression after previous double doses of third-generation TKIs such as Osimertinib.
Any evidence of nervous system failure, including severe encephalopathy, grade 3 or 4 leukoencephalopathy on imaging, and Glasgow Coma Score less than 11.
Any evidence of extensive and lethal progressive systemic diseases without effective treatment.
Patients with poor compliance or other reasons that were unsuitable for this study
Single group
Pemetrexed
DrugPemetrexed 15 mg was administered with dexamethasone 5 mg via intraventricular or via lumbar puncture. First, induction intrathecal chemotherapy, twice per week for 2 weeks; then consolidation intrathecal chemotherapy, once per week for 4 weeks; and maintenance intrathecal chemotherapy, once per month until disease progression or unmanageable drug-related toxicity.
Clinical response rate
The response assessment in neuro-oncology criteria (RANO) proposal for response criteria of leptomeningeal metastasis was used to assess the clinical response in this study.
Neurological progression-free survival (NPFS)
NPFS was defined as time from the start of treatment until neurological progression or death. The neurological progression was determined based on the RANO proposal evaluation criteria which have been established and published on Neuro Oncol.
Overall survival
Survival time was recorded since the date of patient enrollment. All patients were followed up until death or the end of the study.
Incidence of treatment-related adverse events
The incidence of treatment-related adverse events were measured for determining tolerability and safety. Adverse events (AEs) are evaluated according to the Common Terminology Criteria for Adverse Events (CTCAE, version 4.03). Events of grade 3-5 are defined as moderate and severe adverse events.
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