“Rosette” Argon Laser Phototherapy with Rhodamine 123: A new Method for Eradication of Melanoma Tumors in Nude Mice

Rhodamine 123 (Rh-123) is a mitochondrial specific dye that can be successfully used as a photochemosensitizing agent for the argon laser treatment of human melanoma in vitro. In this study a new technique of “Rosette” treatment with the argon laser was developed to completely eradicate human melanoma (M24) tumor transplants in nude mice after “sensitization” with a nontoxic dose of Rh-123. Each experimental group included 4 nu/nu mice injected subcutaneously with 10 millions cells/site for a total of 48 sites. Tumor take was >95% at one week with >10 mm3 tumor volume at each site. Control groups of untreated M24 tumors and M24 tumors sensitized with lug/ml of Rh-123 demonstrated significant growth during the 10 weeks follow-up. Test groups were sensitized with Rh-123 (1ug/ml for one hour) by intratumor injection at one week then treated with the argon laser at 514.5 nm. To allow uniform delivery of energies to the tumors and its edges, a new “Rosette” technique was developed. The tumors were then exposed to non-thermal levels of 700J/cm2 (36°C) or 950J/cm2 (40°C) as determined by a reproducible method of dosimetry. All 16 tumors in this test group showed complete regression with excellent healing and no recurrences even after ten weeks follow-up. Control tumors treated with the argon laser alone, exhibited regrowth at 4 weeks after treatment.