Cancer arising outside the central nervous system (CNS) can metastasize to any intracranial structure, including the membranes covering the brain. These membranes consist of the dura mater, and the arachnoid and pia mater, the latter two together are called the leptomeninges. The subarachnoid space lies between the arachnoid and pia mater and contains the cerebrospinal fluid (CSF) and arteries supplying the brain parenchyma. When tumor invades the leptomeninges, tumor cells can be disseminated via the CSF and spread throughout the subarachnoid space, causing multifocal signs and symptoms.
The treatment of leptomeningeal metastases from solid tumors is reviewed here. The pathophysiology, clinical manifestations, and diagnosis of leptomeningeal metastases, and leptomeningeal involvement in hematologic malignancies, especially large cell lymphomas and acute leukemias, are discussed separately. (See "Clinical features and diagnosis of leptomeningeal metastases from solid tumors" and "Clinical presentation and diagnosis of secondary central nervous system lymphoma", section on 'Leptomeningeal metastasis' and "Involvement of the central nervous system with acute myeloid leukemia".)
GOALS OF TREATMENT
The goals of treatment include stabilizing or improving neurologic function, prolonging survival and if these are not possible, palliating symptoms. However, the prognosis varies considerably, depending upon the tumor type and extent of both neurologic and systemic disease; these factors can help determine the appropriate therapeutic approach for an individual patient. The key parameters separating poor-risk from good-risk patients are summarized in the table (table 1).
Poor-risk patients — Patients with a low Karnofsky performance status (KPS) (table 2), multiple, serious, fixed neurologic deficits, and extensive systemic cancer with limited therapeutic options have a poor prognosis even with active treatment. Management of leptomeningeal metastases in this setting focuses on alleviating symptoms. A palliative approach should also be considered for patients with leptomeningeal gliomatosis and those with encephalopathy due to extensive brain infiltration (carcinomatous encephalitis), since the prognosis is poor even with combined modality therapy [1,2].
The palliative regimen can include the following components: