Ionizing radiation has an effect on health and genetics and its recently used as therapy for different types of cancer. The study aimed to investigate the effect of therapeutic radiation on the tumor suppressor gene, TP53Three regions of TP53 were investigated, exon-7, intron-7 and exon-8. A total of 77 cancer patients who had radiation therapy were examined in this study for genetic analysis with 80 healthy volunteers (control). Genetic testing was carried out before and after radiation treatment. Three ml of blood sample was taken from each patient for the purpose of DNA extraction. In blood cell DNA, TP53 was PCR amplified and sequenced to check any mutation which may occur after radiation. The result demonstrated short-term radiation there was no significant mutation in TP53 gene after radiation therapy. However, there was a novel mutation indicated in the area of the study, in intron-7 region of TP53 gene, C14166T. This mutation was for the first time observed in the study area and in the world. The mutation exists in both health control (26.6%) and cancer patients (73.3%). The female gender experienced a higher rate (60% ) of this mutation than male at the rate and it's more common in breast cancer patients, 33.3%. It is observed in patients older than 40 at 66.6%. Short-term radiation therapy may not cause a serious gene mutation in patients undergoing radiotherapy. A novel mutation in TP53 exists in the study area which is more common in cancer patients. This novel mutation is higher in females and in old ages. This single mutation might be useful in the future to be used as a diagnostic marker and this needs more study to investigate.