ESTRO 2024 - Abstract Book

S2073

Clinical - Sarcoma, skin cancer, melanoma

ESTRO 2024

10

Mini-Oral

Preservation of vision with fully fractionated stereotactic RT for posterior choroidal melanoma.

Claire Phillips 1,2 , Elena Ungureanu 3 , Mathias Bressel 4,5 , Roderick O'Day 6 , John McKenzie 6 , Daniel McKay 6 , Haris Ahmad 2 , Lotte Fog 7 , Joseph Sia 1,8 , Fred Chen 9 , William Campbell 7 1 University of Melbourne, Sir Peter MacCallum Department of Oncology, Parkville, Australia. 2 Peter MacCallum Cancer Centre, Radiation Oncology, Melbourne, Australia. 3 Peter MacCallum Cancer Centre, Physical Sciences, Melbourne, Australia. 4 Peter MacCallum Cancer Centre, Centre for Biostatistics and Clinical Trials, Melbourne, Australia. 5 University of Melbourne, SIr Peter MacCallum Department of Oncology, Melbourne, Australia. 6 The Royal Victorian Eye and Ear Hospital, Ocular Oncology Research Unit, East Melbourne, Australia. 7 The Royal Victorian Eye and Ear Hospital, Ocular Oncology, East Melbourne, Australia. 8 Peter MacCallum Cancer Centre, Radiation Onclogy, Melbourne, Australia. 9 University of Western Australia, Lions Eye Institute, Nedlands, Australia

Purpose/Objective:

Stereotactic radiotherapy (SRT) is an alternative to proton beam therapy for choroidal melanoma (CM) in close proximity to the optic nerve (ON). 1 SRT dose-fractionation regimens (50-70Gy in 4 - 5 fractions over 1 week) were adopted from protons. These are ablative and cause high rates of vision loss when the PTV includes the ON. The risk of vision loss has been correlated with dose to the ON and deterioration of visual acuity to <= 6/60 is expected. 2 A pilot study of standard fractionation SRT combined with a reduced biologic effective dose was conducted to explore if vision could be preserved without compromising survival. Registered on the Australian New Zealand Clinical Trials Registry (ANZCTR): 12614000531617

Material/Methods:

Twenty adults aged <=70 with untreated T1- T2 M0 posterior CM and without diabetes mellitus were accrued from December 2014 to May 2020. 60Gy in 30 fractions SRT was delivered on a stereotactic LINAC. A light and video camera system was used for eye-fixation at simulation and treatment. 3 Simulation CT and MRI scans of the orbit were fused in BrainLab® iplan version 4.5. GTV was defined on MRI, supplemented by fundoscopy and beta ultrasound tumour measurements. GTV to PTV expansion margin was 2-3mm. Treatment planning was carried out in iplan 4.5 using a dynamic conformal arc technique. At least 99% of the PTV was to receive 60Gy,

Results:

Median patient age was 45.5 [range 19.0-63.0]. All tumours were <= 3mm from the macula and/or optic disc. Tumour biopsies were not able to be obtained. Median tumour height was 2.2mm (range 1.0-4.4 mm) and median basal diameter was 8.2mm (range 4.3-15.0 mm). Mean dose to the PTV was 64.95Gy (SD 2.16) and Mean Dmax to the ipsilateral ON was 66.50Gy (SD 3.53). Table 1 presents PTV and ipsilateral organs-at-risk DVH parameters.