Phototherapy with argon lasers and Rhodamine-123 for tumor eradication.

The effectiveness of Rhodamine-123 (Rh-123) as a new photochemosensitizing agent for the argon laser treatment of human melanoma and squamous carcinoma cells in vitro was recently demonstrated. In this study, a new technique of "rosette" treatment with the argon laser was developed to completely eradicate human squamous carcinoma (P3) tumor transplants in nude mice after chemosensitization with Rh-123. Each group included four nu/nu mice injected subcutaneously with 10(7) P3 carcinoma cells/site for a total of 48 sites. Tumor take was greater than 95% at one week, with greater than 10 mm3 tumor volume at each site. Test groups were sensitized with Rh-123 (1 microgram/ml for 1 hour) by intratumor or intraperitoneal injection at 1 week and then treated with the argon laser at 514.5 nm. To allow uniform delivery of energies to the tumor and its edges, a new "rosette" technique was developed. The tumors were then exposed to nonthermal levels of 700 J/cm2 (36 degrees C) or 950 J/cm2 (40 degrees C) as determined by a new and reproducible method of dosimetry. All 16 tumors in this test group showed complete regression with excellent wound healing at 2 weeks and no recurrences, even after an 8 week followup. These results demonstrate that effective eradication of tumors can be achieved in vivo only after sensitization with Rh-123 and specific argon laser treatment ("rosette"), even at nonthermal levels of energies. The high effectiveness of this technique and low toxicity of Rh-123 may render its clinical use very attractive for the treatment of superficial malignancies.