Dose-response relationship for lung cancer induction at radiotherapy dose

Cancer induction after radiation therapy is a severe side effect. It is therefore of interest to predict the probability of second cancer appearance for the treated patient. Currently there is large uncertainty about the shape of the dose-response relationship for carcinogenesis for most cancer types at high dose levels. In this work a dose-response relationship for lung cancer is derived based on (i) the analysis of lung cancer induction after Hodgkin's disease, (ii) a cancer risk model developed for high doses including fractionation based on the linear quadratic model, and (iii) the reconstruction of treatment plans for Hodgkin's patients treated with radiotherapy. The fitted model parameters for an α/β=3 Gy were α=0.061Gy(-1) and R=0.84. The value for α is in agreement with analysis of normal tissue complications of the lung after radiation therapy. The repopulation/repair parameter R is large, but seems to be characteristic for lung tissue which is sensitive with regard to fractionation. Lung cancer risk is according to this model for small doses consistent with the finding of the A-bomb survivors, has a maximum at doses of around 15 Gy and drops off only slightly at larger doses. The predicted EAR for lung after radiotherapy of Hodgkin's disease is 18.4/10000PY which can be compared to the findings of several epidemiological studies were EAR for lung varies between 9.7 and 21.5/10000PY.