Individual Radiosensitivity and Its Relevance to Health Physics

In the radiation protection industry, dose limits are developed to keep workers safe. These limits assume that people have equal responses to ionizing radiation and that there is no variation in radiation risk. However, in radiotherapy, where patients receive large doses of radiation to their tumours and the surrounding tissue volume, variation to a specific treatment plan is well documented in response. Radiation therapy requires increasing the dose to the tumour to kill the cancer, while sparing surrounding normal tissue and reducing side effects. Therefore, therapy regimens are designed to maximize the dose given, yet ensure that 90-95% of patients treated will not have adverse reactions to the therapy. As a result, 5-10% of patients will have adverse reactions. These reactions include an increase in toxicity in the tissue surrounding the tumour, necrosis, loss of organ function or even death. Patients with adverse reactions to radiotherapy are classified as radiation sensitive. Currently the specific cause of this sensitivity is speculative.