527P - Efficacy of intraventricular chemotherapy with pemetrexed for leptomeningeal metastasis from lung adenocarcinoma: A retrospective study

Background

Leptomeningeal metastases (LM) of lung cancer represent a severe neurological complication with a poor prognosis and limited effective treatments. Although intraventricular chemotherapy (IVC) is the preferred management for LM, there is currently insufficient data to support its effectiveness.

Methods

We conducted a retrospective study that analyzed data from consecutive patients with LM from lung adenocarcinoma who underwent Ommaya reservoir insertion at the Nanjing Chest Hospital between 2020 and 2022. The diagnosis of LM was based on either cerebrospinal fluid (CSF) cytology or concordant clinical and neuroimaging findings. The chemotherapy regimen consisted of pemetrexed (30mg or 50mg) and dexamethasone (5mg) administered twice a week for up to 2 weeks during the induction phase, followed by a maintenance phase once a month until progression or maximal doses were reached.

Results

We retrospectively analyzed 56 patients (median age, 56 years) with driver gene mutations, including 46 patients with EGFR mutations, 2 patients with other gene mutations, and 8 patients with non-driver genes. Of the patients, 48.3% had an ECOG PS of 4, 35.7% had an ECOG PS of 3, and 16% had an ECOG PS of 2. Additionally, 41 patients (73.2%) received a 30mg dose of pemetrexed, and 15 patients (26.8%) received a 50mg dose. In all patients, 31 had a response, 19 had stable disease (SD), and 6 had disease progression (PD), resulting in an overall response rate (ORR) of 55.4% and a disease control rate (DCR) of 89.3%. The median progression-free survival (mPFS) was 6.8 months, and the median overall survival (mOS) was not reached. Subgroup analysis showed that the mPFS for the pemetrexed 50mg and 30mg groups was 12 months and 6.8 months, respectively (p=0.006), and the mPFS was 9.6 months versus 4 months in the ECOG PS of 2-3 and 4 arms（Fig1B）, respectively (p=0.001). The overall adverse event (AE) rate was 65%, with all adverse effects, including nausea, vomiting, seizures, and myelosuppression, being mild and transient.

Conclusions

In this real-world study, IVC with pemetrexed demonstrated excellent and encouraging results in patients with lung adenocarcinoma and LM, at an acceptable cost of toxicity.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.