gms | German Medical Science

48th Meeting of the Particle Therapy Co-Operative Group

Particle Therapy Co-Operative Group (PTCOG)

28.09. - 03.10.2009, Heidelberg

Incidence of Neovascular Glaucoma after proton beam therapy of uveal melanoma using anterior structure sparing techniques of the eye

Meeting Abstract

  • I. Daftari - Radiation Oncology, University of California- San Francisco, San Francisco, USA
  • R. Rajendran - Radiation Oncology, University of California- San Francisco, San Francisco, USA
  • K. Mishra - Radiation Oncology, University of California- San Francisco, San Francisco, USA
  • J. R. Castro - Radiation Oncology, University of California- San Francisco, San Francisco, USA
  • J. M. Quivey - Radiation Oncology, University of California- San Francisco, San Francisco, USA
  • T. L. Phillips - Radiation Oncology, University of California- San Francisco, San Francisco, USA
  • D. H. Char - Ophthalmology, Tumori Foundiation & Stanford University, San Francisco, USA

PTCOG 48. Meeting of the Particle Therapy Co-Operative Group. Heidelberg, 28.09.-03.10.2009. Düsseldorf: German Medical Science GMS Publishing House; 2009. Doc09ptcog048

DOI: 10.3205/09ptcog048, URN: urn:nbn:de:0183-09ptcog0488

Published: September 24, 2009

© 2009 Daftari et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.en). You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.


Outline

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Background: We previously hypothesized that reducing the dose to the anterior segment of the eye would reduce the incidence of neovascular glaucoma (NVG). To test this hypothesis, we examined the incidence and factors contributing to NVG in patients treated with proton beam therapy (PBT) using specific anterior segment sparing techniques versus those treated by helium ion particle therapy.

Materials/methods: 559 uveal melanoma patients were treated at Tumiri Foundation/UCSF with PBT between January 1996 and December 2006. Thirty-one patients were excluded due to prior surgical resection and 6 patients because they were treated after I125 plaque therapy. This resulted in 522 evaluated patients treated with anterior segment sparing techniques. All the patients received a dose of 56 GyE in four fractions. The mean follow-up was 51.1±34 months, (range 6 to 152 months). The NVG complication rate was analyzed using univariate and multivariate ststistics, according to risk factors including tumor largest diameter, tumor location, sex, age, percent of anterior chamber in the field(PLF), percent of ciliary body receiving =50% dose (Cil50), percent of optic disc receiving =50% dose (Disc50) , percent of macula receiving = 50% dose (Mac50). The log rank test was used to compare distributions of occurrence of NVG.

Results: 60 patients (11.5%) developed NVG. Enucleation was required for NVG in 9 patients. The risk of NVG peaked around 1.8 years post-treatment. By univariate and multivariate analysis, the largest tumor diameter and tumor height strongly correlated with the development of NVG. Other contributing factors were distance to disc, and fovea and ciliary body involvement. The Kaplan-Maier (K-M) rates of NVG and enucleation at 3 and 5 years were 10% and 15% and 7.2% and 14.4% respectively. With largest tumor diameter less than 10 mm , 10–<16 mm, and =16 mm, the 5 year probability of remaining free of NVG was 89%, 84%, and 65% respectively (p<.0001). With PLF = 0, there was lower probability of NVG (P<0001). 5 year K-M estimates of NVG for tumor-optic disc and tumor-fovea distances of 0mm and >0 mm were 72.6% and 88.1% to the disc and 77.1% and 87.7% to the fovea. If <100% of the macula and optic disc and less than 30% of Cil50 received at least 50% of the dose, the NVG outcome was more favorable (p=.005, p=.0001 and p<.0001). The factors, patient age, gender or the eye involved were not predictors of NVG in univariate or multivariate analysis.

Conclusions: In our previous study we had shown that 35% of patients treated with helium ion therapy for uveal melanoma without anterior structure sparing techniques develop NVG. The data demonstrate that by sparing the anterior structures in the eye, the rate of NVG reduced to 15% at 5years. Additional new findings are the strong influence of ciliary body dose and the effect of irradiation of the macula or the disc on NVG risk.