Iodine-125 plesiotherapy for murine tumor treatment

BACKGROUND: Radiotherapy (RT) is one of the four pillars of cancer treatment. Plesiotherapy, or contact brachytherapy, involves irradiating a tumor by placing small radioactive sources directly on the skin's surface above the tumor. In this study, we evaluated the efficacy of a novel local external radiation technique using iodine-125 seeds enclosed within a 3D-printed case, positioned externally on the tumor surface. METHODS: First, the protocol was tested on the skin of NodRag1 mice with doses up to 10 Gy (at the skin), and the results demonstrated no signs of skin toxicity. Subsequently, this protocol was used to locally irradiate subcutaneous MDA-MB-231 triple-negative breast cancer and MCA-205 fibrosarcoma tumors via a single 10 Gy dose at the tumor center. RESULTS: RT significantly hindered tumor growth, with irradiated tumors being approximately half the size of nonirradiated tumors on the same day. Importantly, the irradiated mice exhibited no apparent systemic side effects, as evidenced by stable body weight and unaffected behavior, including alertness, appearance, and activity levels. Moreover, no instances of skin toxicity were observed. CONCLUSIONS: This in vivo plesiotherapy protocol offers a straightforward and cost-effective means of advancing research on RT in a variety of laboratory settings.