Palliative Radiation Therapy for Leptomeningeal Carcinomatosis

Approximately 5–10% of all patients with cancer will develop leptomeningeal metastasis (LM), often synchronously with parenchymal brain metastases and extracranial disease progression. The vast majority are symptomatic. Recent attempts to subclassify LM reveal that different relapse patterns have distinct aetiology, prognosis and potential treatment options. Palliative radiotherapy is used to address pain or neurologic deficits, control coexisting bulky disease and correct regional areas of impaired CSF flow when patients are being considered for intrathecal therapy. The intent of RT is to stabilize or improve symptoms in the short term; definitive evidence supporting a survival benefit remains elusive. Much of the literature is composed of retrospective single-institution reviews of patients with various histologies treated heterogeneously, confounded significantly by selection bias, resulting in lack of evidence supporting a definitive treatment approach. Optimal dose fractionation is unknown, and no convincing prognostic significance has been associated with radiation volume, dose or technique. Emerging evidence suggests a possible role for proton craniospinal irradiation in solid tumour LM but confirmatory data are required. Patient-reported outcomes regarding neurologic function, cognition and quality of life remain scarce. It will be necessary to reevaluate radiotherapy indications, methods and timing in future with respect to modern systemic agents, including immunotherapy.