Within the last 10-15 years there have been significant developments in the understanding of cancer and the use of radiotherapy for its treatment.Radiotherapy has traditionally involved the use of beams of X-rays,gamma-rays or electrons, from linear accelerators (linacs)-known as teletherapy;or implanting or inserting radioactive sources either directly into tumours or to body cavities nearby-known as brachytherapy.Recent technological developments have changed the treatment options available within radiotherapy to allow much higher doses to be delivered to tumours while sparing normal healthy tissue.The introduction of better imaging techniques has also allowed a clearer understanding of the location of tumours at the point of treatment.However these new technologies are presenting challenges to the existing equipment available within a radiotherapy physics department which is used to measure the radiation dose.This talk will provide a brief overview of the recent developments within radiotherapy, along with the associated challenges these developments present.The talk will highlight some potential applications in which optical fibre sensors may be able to provide useful information currently unavailable with existing equipment, in addition to some preliminary results we have obtained from one such fibre sensor.