Radiation dose at the eye lens of patients undergoing radiation therapy for head and neck cancer.

Linear accelerator irradiation, the most common treatment for head and neck cancer, requires accurate prediction of lens radiation doses to ensure patient safety. The eye lens, being highly radiosensitive and vulnerable to scattered radiation, is at increased risk of developing cataracts. This study compared radiation doses calculated by the treatment planning system (TPS) with those measured in vivo using optically stimulated luminescence (OSL) dosimeters placed on the eyes of 18 patients undergoing radiotherapy for various head and neck cancers. Bland-Altman analysis was used to assess the agreement between the two methods. The results showed that TPS-calculated doses were significantly higher than OSL-measured doses, with TPS values averaging twice as high. However, in three cases, the measured OSL doses exceeded the TPS predictions. The Bland-Altman plot revealed poor agreement between the two methods. The mean doses to the left and right eye lenses were 182 cGy and 170 cGy, respectively, with the highest recorded doses being 492 cGy for the left eye and 513 cGy for the right eye. Patients with nasopharyngeal cancer received the highest doses, and four patients had doses in the 3-5 Gy range, increasing their risk of cataracts. These findings emphasize the importance of validating TPS accuracy in clinical practice to ensure optimal patient care. Further research is necessary to explore the discrepancies between dose measurements and enhance TPS precision, improving clinical outcomes and patient safety in radiation therapy.