Dosimetric analysis of intraocular hemorrhage in nonsquamous head and neck cancers treated with carbon-ion radiotherapy.

Abstract

Carbon-ion radiotherapy is an attractive treatment option for unresectable/inoperable, nonsquamous cancers of the head and neck. Intraocular hemorrhage associated with carbon-ion radiotherapy for head and neck cancer is largely an unresearched area; hence, we investigated its incidence and predictive factors. We evaluated 79 patients (i.e., 158 eyes) with nonsquamous cancers of the head and neck treated by carbon-ion radiotherapy with a follow-up period of ≥12 months. Dosimetric parameters such as D_max, D_mean and V_d [volume irradiated with "d" Gy (RBE)] and age, gender, primary site, histology and comorbidities were analyzed as predictors of intraocular hemorrhage. Seven (8.9%) of 79 patients (158 eyes) developed intraocular hemorrhage with a median latent period of 24 months (range, 15-47 months). The 5-year cumulative incidence of intraocular hemorrhage was 6%. D_max and V_10-60 for eyeballs, retina and optic nerves were significantly higher in intraocular hemorrhage group than the rest (p <0.001 for D_max and V_10-60). On univariate analysis, V₄₀ ≥0.83 cm³ and ≥0.66 cm³ (p = 0.001) and D_max ≥54.75 Gy (RBE) and ≥54.58 Gy (RBE) (p = 0.002) for eyeball and retina, respectively, were predictors of intraocular hemorrhage. Additionally, maxillary primary (p = 0.025) and younger age (age <60 years, p = 0.048) were significant risk factors for intraocular hemorrhage. Dosimetric parameters such as V₄₀ and D_max for the eyeball, retina and maxillary sinus primary and younger age were significant predictors of intraocular hemorrhage following carbon-ion radiotherapy.