Radiotherapeutic Bandage for the Treatment of Skin Cancer

Purpose: It is currently estimated that one in every five Americans will develop skin cancer. Squamous cell carcinoma (SCC) is the second most common type of skin cancer and occurs in cells just beneath the outermost layer of the epidermis. Radiation therapy is used in the clinic against inoperable tumor lesions and in patients that cannot undergo surgery, as well as to treat recurring lesions after a primary surgical approach (i.e., Mohs micrographic surgery). We have previously reported on the incorporation of Holmium-165 (165Ho) nanoparticles into electrospun nanofibrous mats (“bandages”) for potential use in the treatment of SCC. A 165Ho-containing polymer nanofibrous bandage was prepared via electrospinning using 165Ho-iron garnet nanoparticles (165HoIG) and polyacrylonitrile. These bandages can be manipulated for easy application to tumor lesions, and can be made on a large scale; they are made radioactive (to holmium-166; 166Ho) just prior to therapy using a process called neutron-activation. The goal of the present study is to test our radiotherapeutic bandage against SCC in an animal model, to determine clinical relevance. Methods: Polyacrylonitrile polymer bandages containing 165HoIG were prepared as previously reported. The radiotherapeutic bandages were then produced via neutron-activation in a thermal neutron flux of 1.8 × 1013 neutrons/cm2·s for 1.33 h using a 1 MW nuclear reactor. Female athymic nude mice were injected with human Colo-16 SCC cells subcutaneously and after eight days (average tumor volume: 35 ± 8.6 mm3) received no treatment, or were exposed to non-radioactive or radioactive (92.5 ± 18.5 MBq) bandages for approximately 1 h (n = 10 per group). After treatment, tumors were measured over fifteen days, tumor volume ratios (TVRs) compared and histopathology performed. Results: Fifteen days after treatment, the TVR of the radioactive bandage treatment group was 3.3 ± 4.5, while TVRs of the non-radioactive bandage treatment and no treatment control groups were 33.2 ± 14.7 and 26.9 ± 12.6, respectively. At the time of necropsy, there was mild focal epidermal hyperplasia surrounding a small area of epidermal ulceration in the radioactive bandage group. No other examined tissue (i.e., muscle, liver, kidney, lung, spleen and heart) showed significant lesions. Conclusions: Our radiotherapeutic bandage exhibits promising efficacy against SCC of the skin in a mouse model. It can be individually tailored for easy application on tumor lesions of all shapes and sizes, and could complement or possibly replace surgery in the clinic.