Evaluating Dose-response of Cataract Induction in Radiotherapy of Head and Neck Cancers Patients

BACKGROUND: Head and neck cancers are currently the most common types of cancers. 3D-conformal radiation therapy is the most common dose delivery technique for head and neck cancers. Eye Lens is a radio sensitive structure and cataract formation as a visual disorder associated with exposure to ionizing radiation which is documented. OBJECTIVE: Determining the radiation dose to eye lens during head and neck radiography and estimating the probability of cataract induction are essential. MATERIAL AND METHODS: This experimental study was performed on 14 patients with head and neck cancers through experimental study analysis. The maximum opacity of the eyes lens were measured by pentacam(TM) before radiation therapy. CT data of patients were transmitted to Isogray treatment planning Software, and dose calculations for each patient was performed. At the end of radiation treatment, 3 and 6 months after radiotherapy, the eye lens opacity of the patients was assessed. RESULTS: Overall, 28 lenses were studied. Statistical one sample K- S test proved normality of obtained data. Using repeated measures test, the relation before and 3 months after radiotherapy, as well as the relationship before and 6 months after radiotherapy proved a significant relationship. CONCLUSION: The opacity caused by radiation in eyes is a non-statistical and linear-quadratic response curve with no threshold. This opacity can also appear within 3 months after completion of radiation therapy.