A mimetic of the enzyme superoxide dismutase (SOD) that may potentially be used to increase the anti-cancer efficacy of stereotactic body radiation therapy (SBRT). Upon administration, rucosopasem manganese may mimic native SODs and catalyze the formation of molecular oxygen and hydrogen peroxide from the burst of superoxide anion present in the irradiated tissues upon radiation. As hydrogen peroxide is less toxic than superoxide to normal tissues, but more toxic to cancer cells, this may increase the anti-cancer efficacy of SBRT and decrease its damage to normal tissues.