- Patients on therapeutic anticoagulation with coumarins (e.g. warfarin); prophylactic coumarin-based anticoagulation (i.e. low dose warfarin) for venous or arterial access devices is allowed provided that the requirements for prothrombin time (PT), international normalization ratio (INR) and/or partial thromboplastin time (PTT) are met; prophylactic or therapeutic low molecular weight heparin is allowed; patients with known brain metastases are excluded (even if treated and stable) if they are also on therapeutic doses of anticoagulation