EPO and cancer: For instance, erythropoietin (EPO) was known to increase oxygen transportation and hence it was hypothesised that EPO could reduce tumour hypoxia, thus increasing radiosensitivity.9 Another example is nitroglycerin and its proposed role in reducing hypoxia-mediated radioresistance through its known vasodilator effect.10 11 Other drugs were discovered to exert a new MOA irrelevant for the non-cancer indication, but which suggested their utility as radiosensitisers.