Radionuclide therapy of skin cancers and Bowen's disease using a specially designed skin patch

Skin cancer is the most common malignancy in humans. Therapeutic modalities for skin cancer are local destruction, radiotherapy and surgery. External radiation therapy leads to good results, however, generally 5-6 wk of treatment is needed to deliver optimal radiation dose to tumors. In this study, a beta-emitting radionuclide, 166Ho, impregnated in a specially designed patch, was used on superficial skin cancers and Bowen's disease for local irradiation. METHODS: Ten mice with chemically induced skin tumors were studied. Five-millimeter size patches containing 22.2-72.15 MBq (0.6-1.95 mCi) 166Ho were applied to the tumor surface for 1-2 hr. In a human trial, patients with squamous-cell carcinoma (n = 3), basal cell carcinoma (n = 1) and Bowen's disease (n = 1) were treated with patches containing 273.8-999 MBq (7.4-27 mCi) of 166Ho for 30 min to 1 hr. Pathologic examination was performed 4-7 wk after treatment in an animal model. Skin biopsy was performed 8 wk post-treatment in four patients. RESULTS: Tumor destruction was seen 1 wk post-treatment, however, radiation dermatitis or ulceration developed at the site of radionuclide application. Those reactions healed gradually with fibrosis or epithelialization, which was confirmed pathologically. No significant adverse reaction to radiation except subcutaneous fibrosis was found. CONCLUSION: Superficial skin tumors could be successfully treated by topical application of beta-emitting radionuclides.