Risk Assessment of Cataract Development in Radiotherapy for Patients with Brain Tumors and Head and Neck Cancer

Abstract

The lens is one of the organs at risk (OAR) in radiotherapy for brain tumors and the head and neck cancer. The tolerable dose is low compared to other OARs, and in cases where the tumor is near the lens, the tolerable dose will be exceeded. In this study, we retrospectively investigated the development of cataract after radiotherapy in patients with brain tumors and head and neck cancer. Among 76 patients with brain tumor, maxillary sinus cancer, orbital sarcoma, oral cavity cancer, buccal mucosal cancer, and nasopharyngeal cancer, we reviewed follow-up records of 43 patients (86 lenses). These patients were treated in Hirosaki University Hospital. The lens dose was estimated by dose volume histogram calculated using radiotherapy planning system. Among the 43 patients (86 lenses) investigated, 5 patients (6 lenses) developed cataracts (6.98%). Of which, four lenses were from patients with maxillary sinus cancer, one with orbital sarcoma, and one with nasopharyngeal cancer. The univariate analysis using Cox proportional hazards regression was performed to examine the clinical features of cataract development. Sex, age, smoking, drinking alcohol, and hypertension, which were reported to be associated with the onset of the cataract, were not significantly correlated in this study. Only lens dose classified according to tolerable dosage of 1,000 cGy was significantly associated (P = 0.048), with a hazard ratio of 8.830 (95% CI: 1.020–76.440). The cumulative incidence function indicated that the incidence was significantly higher in the sub-group that exceeded the tolerable dose (P = 0.020). In addition, there was a negative correlation between lens dose and latent period (r = -0.521). The median lens dose was the highest for orbital sarcoma (1973.2 cGy), followed by maxillary sinus cancer (1425.1 cGy). Additionally, the median lens dose in brain tumors exceeded the tolerable dose (1243.4 cGy). In comparison with the 3 dimensional-conformal radiotherapy, the lens dose was lower and no patients developed cataract in the intensity modulated radiotherapy (IMRT) method. Radiotherapy for tumors located in close proximity to the lens often results to a high lens dose, with many instances exceeding the tolerable dose, thereby increasing the risk of developing cataracts. Conversely, employing the IMRT technique has demonstrated the ability to reduce lens dose and risk of cataract development.