Apparatuses and methods described herein relate to treating cancerous tumors using radiation therapy and chemotherapy. In some embodiments, a method of treatment includes administering radiation therapy targeting a tumor, isolating a segment of a vessel proximate to the tumor, and administering a dose of a chemotherapeutic agent to the segment of the vessel. The method can further include waiting a period of time after administering the radiation therapy before administering the dose of the chemotherapeutic agent. In some embodiments, a catheter device including first and second occluding elements can be used to isolate the segment of the vessel.