301 Patients receiving radiotherapy for head and neck cancer may be at a greater risk of developing cataracts due to radiation exposure to the eye lens, a recent study has found. Researchers examined radiation doses measured directly from patients and compared them with those predicted by treatment planning systems. The findings raise concerns about the accuracy of these systems and highlight the need for improved radiation dose monitoring. The findings were published in the journal Radiological Physics and Technology. Head and neck cancer is among the most common cancers worldwide, often requiring radiotherapy as a primary treatment. While radiation is essential for targeting tumours, it can also affect surrounding healthy tissues, including the highly sensitive eye lens. The study assessed 18 patients undergoing radiotherapy and found significant differences between predicted and actual radiation doses received by the eye lenses. In many cases, the system overestimated doses, but in some instances, actual exposure exceeded predictions. The research team used optically stimulated luminescence dosimeters to measure real-time radiation exposure to patients’ eye lenses. Results showed that treatment planning systems, which are commonly used to predict radiation doses, frequently provided higher estimates than those recorded by the dosimeters. However, in three cases, the actual radiation received was greater than the predicted dose, raising concerns about patient safety. According to the study, the mean radiation dose to the left eye lens was 182 centigray, while the right eye lens received an average of 170 centigray. The highest recorded doses reached 492 centigray for the left eye and 513 centigray for the right eye. Notably, patients with nasopharyngeal cancer were exposed to the highest levels of radiation, likely due to the proximity of tumours to the eyes. Four patients in the study received doses in the range of three to five gray, a level considered high enough to significantly increase the risk of cataract development. Cataracts, a leading cause of vision impairment, occur when the eye lens becomes clouded over time. The International Commission on Radiological Protection has identified 50 centigray as the minimum threshold at which radiation exposure can increase the likelihood of cataracts. The study found that many patients exceeded this threshold, suggesting that current radiotherapy protocols may not provide sufficient protection for the eyes. Another key finding was that the positioning of the tumour significantly influenced the level of radiation exposure to the eye lens. Tumours closer to the eye, particularly in the nasopharynx, were linked to higher radiation doses. The study also noted discrepancies in dose distribution, with some patients receiving uneven exposure between their left and right eyes. The researchers concluded that treatment planning systems require further refinement to improve accuracy and ensure patient safety. While these systems remain a vital tool for radiotherapy, the findings suggest that additional monitoring methods should be incorporated to verify actual radiation exposure levels. The study emphasised the importance of routine validation of radiation dose predictions to minimise risks associated with treatment. Experts in radiotherapy and oncology are calling for further research into improving treatment planning accuracy. By enhancing the precision of radiation delivery, it may be possible to reduce unnecessary exposure to the eyes and other vulnerable areas, ultimately improving outcomes for patients undergoing treatment for head and neck cancer.