ESTRO 2024 - Abstract Book

S5916

RTT - Service evaluation, quality assurance and risk management

ESTRO 2024

1857

Digital Poster

Ruthenium-106 brachytherapy for uveal melanoma: impact of dose deviations

Heloisa H Deuzeman 1 , Marina Marinkovic 2 , Lennart J Pors 1 , T H Khanh Vu 2 , Ellen M Kerkhof 1 , Coen RN Rasch 1 , Jacob C Bleeker 2 , Carien L Creutzberg 1 , Jan-Willem M Beenakker 1,2,3 , Gre PM Luyten 2 , Nanda Horeweg 1,2 1 Leiden University Medical Center, Radiation Oncology, Leiden, Netherlands. 2 Leiden University Medical Center, Ophthalmology, Leiden, Netherlands. 3 Leiden University Medical Center, Radiology, Leiden, Netherlands

Purpose/Objective:

Small to intermediate-sized choroidal melanomas are treated with Ruthenium-106 brachytherapy. Delivery of the correct dose is crucial for local tumour control and minimizing adverse effects. Application time is determined by tumour thickness, applicator type and activity at the time of treatment. We investigated differences between planned and actual application time, and impact of dose deviations.

Material/Methods:

All patients treated for choroidal melanoma at our national referral institute between January 2012 and April 2014 were included in a prospective database, as part of our ongoing 2012-2022 evaluation. 6 different types of Ru-106 plaques (Bebig, Germany) were used and placed under general anaesthesia, and usually removed under local anaesthesia. The prescribed dose was 130Gy-equivalent (>110Gy physical dose) to the tumour apex, with a maximal dose to the scleral surface of 1000-1200Gy-equivalent. A dose correction was used to account for differences in doses rate with time. For large tumour prominences, scleral surface doses >1200Gy were accepted to reach tumour apex dose >110Gy. For thin tumours, scleral surface doses were kept at a minimum of 300Gy for 130Gy to the apex. Deviations up to 5% of the planned treatment time were deemed acceptable. Actually delivered doses were calculated using the actual application times. Time to event data were assessed using Kaplan-Meier’s methodology. Differences between continuous variables were tested using the Wilcoxon signed-ranks test.

Results:

172 patients were analysed, their characteristics are presented in Table 1. Median follow-up was 9.8 years. Survival probability after 5 years was 82%. 5-year risk of metastases was 14% while risk of local recurrence after 5 years was 7%, and 5-year risk of enucleation was 3%.

Characteristics

N=172 (100%)

Age (years)

64 (20-88)

Gender (female)

91 (53%)