A retrospective analysis of first-line PD-1 monoclonal antibodies treatment in patients with leptomeningeal metastasis from solid tumors.

Introduction: Patients whose solid tumors (ST) show leptomeningeal metastasis (LM) have very poor prognosis and short overall survival. The aim of this study was to evaluate the efficacy of first-line programed death-1(PD-1) monoclonal antibody (mAb) treatment in these patients.
Methods: We retrospectively evaluated patients diagnosed with LM from ST who were treated with first-line PD-1 mAb at our hospital between April 1 and November 30, 2019. We analyzed their clinicopathological characteristics and response to the treatment.
Results: We collected and analyzed data from 6 patients with different primary ST. 5 patients received PD-1 mAb combined with chemotherapy and/or anti-angiogenic drugs, while one received only PD-1 mAb. The median (range) number of treatment cycles was 5.5 (1-21). PD-1 mAb treatment did not cause neurotoxicity. The time period of first assessment varied from 21 to 65 days after treatment. Among 5 patients who got obvious symptoms relief, 4 patients persisted for > 3 months and even showed a reduction in the number of tumor cells in cerebrosprinal fluid. Ventriculoperitoneal (VP) shunt was used to treat hydrocephalus observed beneficial in 3 patients: 2 before and 1 after PD-1 mAb treatment. The median (range) follow-up time was 214 (57-460) days. 4 patients died. The overall survival ranged from 57 days to at least 460 days. 1 of the two alive patients continued to show no worsening of symptoms after 457 days.
Conclusions: Patients with LM from ST can benefit from first-line PD-1 mAb combined treatment without additional neurotoxicity. Further research is required to validate the safety and efficacy.