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.