Radiobiology of low-dose-rate radiation relevant to radioimmunotherapy

Systemically delivered targeted radioisotopes are being used ever-increasin gly for cancer therapy. Compared with conventional external beam radiation therapy, the radiation dose-rate associated with these novel systemic thera pies is approximately two orders of magnitude lower in intensity (dose-rate ). Hence it is referred to as low dose-rate (LDR) radiotherapy. An awarenes s of the unique radiobiology associated with LDR-based therapy provides a b asis for cautious enthusiasm as these new therapies are explored.