Clinical-Dosimetric relationship between lacrimal gland dose and ocular toxicity after intensity-Modulated radiotherapy for sinonasal tumours

Objective: To characterise the relationship between lacrimal gland dose and ocular toxicity among patients treated by intensity-modulated radiotherapy (IMRT) for sinonasal tumours. Methods: 40 patients with cancers involving the nasal cavity and paranasal sinuses were treated with IMRT to a median dose of 66.0Gy. Toxicity was scored using the Radiation Therapy Oncology Groupmorbidity criteria based on conjunctivitis, corneal ulcerationandkeratitis. Thepaired lacrimal glands were contoured as organs at risk, and the mean dose, maximum dose, V₁₀, V₂₀ and V₃₀ were determined. Statistical analysis was performed using logistic regression and the Akaike information criterion (AIC). Results: The maximum and mean dose to the ipsilateral lacrimal gland were 19.2Gy (range, 1.4-75.4Gy) and 14.5Gy (range, 11.1-67.8Gy), respectively. The mean V₁₀, V₂₀ and V ₃₀ values were 50%, 25% and 17%, respectively. The incidence of acute and late Grade 3+ toxicities was 23% and 19%, respectively. Based on logistic regression and AIC, the maximum dose to the ipsilateral lacrimal gland was identified as a more significant predictor of acute toxicity (AIC, 53.89) and late toxicity (AIC, 32.94) than the mean dose (AIC, 56.13 and 33.83, respectively). The V₂₀ was identified as the most significant predictor of late toxicity (AIC, 26.81). Conclusion: A dose-response relationship between maximum dose to the lacrimal gland and ocular toxicity was established. Our data suggesting a threshold relationship may be useful in establishing dosimetric guidelines for IMRT planning that may decrease the risk of acute and late lacrimal toxicities in the future. Advances in knowledge: A threshold relationship between radiation dose to the lacrimal gland and ocular toxicity was demonstrated, which may aid in treatment planning and reducing the morbidity of radiotherapy for sinonasal tumours.