Blood Flow in Transplantable Bladder Tumors Treated with Hematoporphyrin Derivative and Light¹ Free

Following hematoporphyrin derivative (HPD) photochemotherapy, blood flow to transplantable N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide-induced urothelial tumors was determined by a radioactive microsphere technique using either ¹⁰³Ru or ¹⁴¹Ce. Two tumors were implanted s.c. on the abdominal wall of Fischer 344 weanling rats. HPD (10 mg/kg body weight) was administered 24 hr prior to phototherapy (red light, >590 nm; 360 J/sq cm). One of the two tumors was shielded from light exposure and served as an internal control. Blood flows were determined in control animals that received no treatment (Group 1), HPD only (Group 2), or light only (Group 3). In Groups 4 and 5, animals received the combination of HPD and light but differed in the time interval between treatment and blood flow determinations (10 min and 24 hr, respectively). Only blood flow to tumors treated with HPD and light showed a significant decrease (p < 0.05) when compared with their internal controls both at 10 min (Group 4) and 24 hr (Group 5) after completion of phototherapy. These studies suggest that disruption of tumor blood flow may be an important mechanism of action of this method of cancer therapy.