Intrathecal pemetrexed for leptomeningeal metastases in a patient with ALK-rearranged lung adenocarcinoma: a case report.

Progressive leptomeningeal metastases (LM) are associated with intractable neurological symptoms and a poor prognosis, and effective treatment options are limited. Intrathecal (IT) pemetrexed has been shown to confer clinical benefit in lung adenocarcinoma, yet our understanding of the efficacy and safety of the treatment is limited. We report a patient with a long-standing history of leptomeningeal disease due to ALK-positive adenocarcinoma of the lung, previously controlled by increased doses of lorlatinib (125 mg/day). Rapid LM progression prompted the start of IT pemetrexed, after which the patient experienced immediate clinical improvement. The case provides additional support that IT pemetrexed can offer symptomatic relief and may be considered as a treatment option in advanced LM. Furthermore, the case illustrates that an increased dose of lorlatinib may efficiently control LM in patients with ALK-rearranged NSCLC, following progression on standard lorlatinib dosage.