 - Known brain metastases or leptomeningeal metastases; NOTE: symptomatic, andor if they require immunosuppressive doses of corticosteroids e.g. 10 mgday prednisone or equivalents for at least 2 weeks prior to study drug administration; patients with treated brain metastases who are deemed clinically stable and without radiological progression on positron emission tomography PET, MRI or computed tomography CT scan performed 8 weeks of study entry, are not excluded; NOTE: primary nasopharyngeal cancers that directly invade the skull base and extend into the infratemporal fossa e are not regarded as brain metastases and are not excluded 