title: Stereotactic radiotherapy for unilateral orbital lymphoma and orbital pseudo-tumors: a planning study.
abstract: Orbital lymphoma and Grave's ophthalmopathy (GO) are successfully treated with radiation therapy. The lenses are blocked to prevent cataract formation. However, blocking of the lens by traditional methods can be difficult for tumors located anteriorly and extending into the retrobulbar space. We present a series of 3 patients with orbital lymphoma and 1 with GO treated with stereotactic intensity modulated radiation therapy (IMRT) to spare normal structures, including the lens. Three patients with orbital lymphomas and 1 with unilateral GO were treated with IMRT using a linac with stereotactic capabilities. Avoidance structures included the ipsilateral lens and globe, the contralateral lens and globe, the chiasm, and the brainstem. Two patients with orbital lymphoma were treated with 24 Gy in 12 fractions, and 1 patient was treated with 30.6 Gy in 17 fractions. The patient with GO was treated with 20 Gy in 10 fractions. The dosimetry was analyzed to determine the dose to normal tissues. Patient follow-up varies between 8 and 24 months. The mean minimal dose to the ipsilateral lens was 13.6% of the total dose, the mean maximal dose was 33.5%, and the mean median dose was 19.3%. The mean median dose to the contralateral eye was 1.1% of the total dose. The mean median dose to the chiasm was 14.9% of the total dose. The mean median dose to the brainstem was 1.9% of the total dose. No cataracts or other complications were noted in the 4 patients treated with this technique so far. IMRT gives a more conformal treatment to the orbital contents while sparing normal tissues such as the ipsilateral lens and adjacent critical structures. This should result in fewer complications such as cataracts.
authors.affiliation: Department of Radiation Oncology, University of Arizona Health Sciences Center, Tucson, AZ 85724, USA. kchino@email.arizona.edu
authors.forename: Kazumi
authors.initials: K
authors.lastname: Chino
authors.forename: James A
authors.initials: JA
authors.lastname: Tanyi
authors.forename: Baldassarre
authors.initials: B
authors.lastname: Stea
mesh_terms: D001933:Brain Stem / Q000528:radiation effects; D002386:Cataract / Q000209:etiology / Q000517:prevention & control; D004307:Dose-Response Relationship, Radiation; D049970:Graves Ophthalmopathy / Q000532:radiotherapy*; D006801:Humans; D007908:Lens, Crystalline / Q000528:radiation effects; D008223:Lymphoma / Q000532:radiotherapy*; D009897:Optic Chiasm / Q000528:radiation effects; D009918:Orbital Neoplasms / Q000532:radiotherapy*; D011832:Radiation Injuries / Q000209:etiology / Q000517:prevention & control; D011835:Radiation Protection / Q000379:methods; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects / Q000379:methods*; D013238:Stereotaxic Techniques