metastasis brain leptomeningeal known distant patients symptomatic suspected cns evidence brain metastases known patients treated stable trial excluded clinical evidence disease progression progressive patients evidence leptomeningeal therapy refractory treatment prior nervous central cns metastases active known untreated disease meningitis lymphoma cord spinal compression brain metastases leptomeningeal untreated symptomatic stable disease cns metastases nervous central patients disease stable symptomatic treated brain