[Clinical trials on intrathecal pemetrexed treated leptomeningeal metastases from solid tumors]

Objective: To investigate the feasibility, safety and efficacy of intrathecal pemetrexed (IP) treated for patients with leptomeningeal metastases (LM) from solid tumors. Methods: Forty-seven patients receiving pemetrexed intrathecal chemotherapy in the First Hospital of Jilin University from 2017 to 2018 were selected. The study of pemetrexed intrathecal chemotherapy adopted the classical dose-climbing model and included 13 patients with meningeal metastasis of non-small cell lung cancer who had relapsed and refractory after multiple previous treatments including intrathecal chemotherapy. Based on the dose climbing study, 34 patients with meningeal metastasis of solid tumor who did not receive intrathecal chemotherapy were enrolled in a clinical study using pemetrexed as the first-line intrathecal chemotherapy combined with radiotherapy. Kaplan-Meier method and Log rank test were used for survival analysis, and Cox regression model was used for influencing factor analysis. Results: The dose climbing study showed that the maximum tolerated dose of pemetrexed intrathecal chemotherapy was 10 mg per single dose, and the recommended dosing regimen was 10 mg once or twice a week. The incidence of adverse reactions was 10 cases, including hematological adverse reactions (7 cases), transaminase elevation (2 cases), nerve root reactions (5 cases), fatigue and weight loss (1 case). The incidence of serious adverse reactions was 4, including grade 4-5 poor hematology (2 cases), grade 4 nerve root irritation (2 cases), and grade 4 elevated aminotransferase (1 case). In the dose climbing study, 4 patients were effectively treated and 7 were disease controlled. The survival time was ranged from 0.3 to 14.0 months and a median survival time was 3.8 months. The clinical study of pemetrexed intrathecal chemotherapy combined with radiotherapy showed that the treatment mode of 10 mg pemetrexed intrathecal chemotherapy once a week combined with synchronous involved area radiotherapy 40 Gy/4 weeks had a high safety and reactivity. The incidence of major adverse reactions was 52.9% (18/34), including hematologic adverse reactions (13 cases), transaminase elevation (10 cases), and nerve root reactions (4 cases). In study 2, the response rate was 67.6% (23/34), the disease control rate was 73.5% (25/34), the overall survival time was ranged from 0.3 to 16.6 months, the median survival time was 5.5 months, and the 1-year survival rate was 21.6%. Clinical response, improvement of neurological dysfunction, completion of concurrent therapy and subsequent systemic therapy were associated with the overall survival (all P<0.05). Conclusions: Pemetrexed is suitable for the intrathecal chemotherapy with a high safety and efficacy. The recommended administration regimen was IP at 10 mg on the schedule of once or twice per week. Hematological toxicity is the main factor affecting the implementation of IP. Vitamin supplement can effectively control the occurrence of hematological toxicity.