ANTERIOR SEGMENT SPARING TO REDUCE CHARGED-PARTICLE RADIOTHERAPY COMPLICATIONS IN UVEAL MELANOMA

Purpose: The purpose of this investigation is to delineate the risk fa ctors in the development of neovascular glaucoma (NVG) after helium-io n irradiation of uveal melanoma patients and to propose treatment tech nique that may reduce this risk, Methods and Materials: 347 uveal mela noma patients were treated with helium-ions using a single-port treatm ent technique. Using univariate and multivariate statistics, the NVG c omplication rate was analyzed according to the percent of anterior cha mber in the radiation field, tumor size, tumor location, sex, age, dos e, and other risk factors, Several University of California San Franci sco-Lawrence Berkeley National Laboratory (LBNL) patients in each size category (medium, large, and extralarge) were retrospectively replann ed using two ports instead of a single port, By using appropriate pola r and azimuthal gaze angles or by treating patients with two ports, th e maximum dose to the anterior segment of the eye can often be reduced , Although a larger volume of anterior chamber may receive a lower dos e by using two ports than a single port treatment, We hypothesize that this could reduce the level of complications that result from the irr adiation of the anterior chamber of the eye, Dose-volume histograms we re calculated for the lens, and compared for the single and two-port t echniques, Results: NVG developed in 121 (35%) patients, The risk of N VG peaked between 1 and 2.5 years posttreatment. By univariate and mul tivariate analysis, the percent of lens in the field was strongly corr elated with the development of NVG, Other contributing factors were tu mor height, history of diabetes, and vitreous hemorrhage. Dose-volume histogram analysis of single-port vs, two-port techniques demonstrate that for some patients in the medium and large category tumor groups, a significant decrease in dose to the structures in the anterior segme nt of the eye could have been achieved with the use of two ports, Conc lusion: The development of NVG after helium-ion irradiation is correla ted to the amount of lens, anterior chamber in the treatment field, tu mor height, proximity to the fovea, history of diabetes, and the devel opment of vitreous hemorrhage. Although the influence of the higher LE T deposition of helium-ions is unclear, this study suggests that by re ducing the dose to the anterior segment of the eye may reduce the NVG complications, Based on this retrospective analysis of LBNL patients, we have implemented techniques to reduce the amount of the anterior se gment receiving a high dose in our new series of patients treated with protons using the cyclotron at the UC Davis Crocker Nuclear Laborator y (CNL). (C) 1997 Elsevier Science Inc.