A system (60,120) for perfusing a localized site (61, 122) within a body, the system comprising: (a) a catheter assembly comprising: (i) a venous access line adapted to deliver perfusate to the localized site; (ii) a venous drainage line adapted to recover drainage flow from the localized site; and (iii) an occlusion device (68,78,128) adapted to prevent some or substantially all physiological venous blood flow between the localized site and systemic circulation of the body during and in the course of delivering perfusate to and recovering drainage flow from the localized site; (b) a blood circuit (90,150) associated with the catheter assembly to facilitate blood conditioning for use as the perfusate, in the course of a controlled perfusion and drainage of untreated, treated, or inactivated treated blood to and from the localized site, the circuit comprising: (i) a therapy delivery module adapted to deliver perfusate to the venous access line; (ii) a therapy isolation module adapted to control both the absolute and relative delivery of perfusate to the localized site and drainage from the localized site using the catheter, in a manner that provides perfusate to substantially only the localized site; and (iii) a therapy deactivation module adapted to recover drainage flow in order to deactivate at least a portion of the drainage flow prior to delivery back to the systemic circulation; and (c) a delivery machine adapted to control the blood circuit and catheter assembly in order to both deliver perfusate to, and recover drainage flow from the localized site in a manner that provides perfusate to substantially only the localized site. (a) a catheter assembly comprising: (i) a venous access line adapted to deliver perfusate to the localized site; (ii) a venous drainage line adapted to recover drainage flow from the localized site; and (iii) an occlusion device (68,78,128) adapted to prevent some or substantially all physiological venous blood flow between the localized site and systemic circulation of the body during and in the course of delivering perfusate to and recovering drainage flow from the localized site; (i) a venous access line adapted to deliver perfusate to the localized site; (ii) a venous drainage line adapted to recover drainage flow from the localized site; and (iii) an occlusion device (68,78,128) adapted to prevent some or substantially all physiological venous blood flow between the localized site and systemic circulation of the body during and in the course of delivering perfusate to and recovering drainage flow from the localized site; (b) a blood circuit (90,150) associated with the catheter assembly to facilitate blood conditioning for use as the perfusate, in the course of a controlled perfusion and drainage of untreated, treated, or inactivated treated blood to and from the localized site, the circuit comprising: (i) a therapy delivery module adapted to deliver perfusate to the venous access line; (ii) a therapy isolation module adapted to control both the absolute and relative delivery of perfusate to the localized site and drainage from the localized site using the catheter, in a manner that provides perfusate to substantially only the localized site; and (iii) a therapy deactivation module adapted to recover drainage flow in order to deactivate at least a portion of the drainage flow prior to delivery back to the systemic circulation; and (i) a therapy delivery module adapted to deliver perfusate to the venous access line; (ii) a therapy isolation module adapted to control both the absolute and relative delivery of perfusate to the localized site and drainage from the localized site using the catheter, in a manner that provides perfusate to substantially only the localized site; and (iii) a therapy deactivation module adapted to recover drainage flow in order to deactivate at least a portion of the drainage flow prior to delivery back to the systemic circulation; and (c) a delivery machine adapted to control the blood circuit and catheter assembly in order to both deliver perfusate to, and recover drainage flow from the localized site in a manner that provides perfusate to substantially only the localized site.