Methods, apparatus and compositions are provided for treatment of cancer of a selected organ by intraluminal delivery of oncolytic agents through a blood vessel or duct leading to the cancer tissue. During the time the oncolytic agents are being applied to the targeted tissue downstream, the designated vessel or duct can be selectively occluded to increase concentration and pressure of the applied agents at the target site. Oncolytic compositions including oncolytic viruses formulated with delivery visualization markers are provided.
