ESTRO 2024 - Abstract Book

S5919

RTT - Service evaluation, quality assurance and risk management

ESTRO 2024

In 8 cases, tumour apex dose was below 110Gy. In 6 of these (including 1 which was removed early), apex dose was too low because the maximal scleral surface dose was reached due to tumour prominences 7.6-8.1mm. In the 2 remaining cases, the delivered dose reported is the result of a post-treatment recalculation using a larger tumour prominence than that was available during treatment planning. Of these 8 cases, 2 (25%) had in-field local recurrences, 5 (67.2%) developed metastasis (4 uveal melanoma, 1 of unknown origin), and 4 (50%) patients died. In 3 cases, scleral surface dose was >1200Gy (unrelated to removal time), which did not lead to scleritis or scleral melting. However, 1 patient had grade 1, and 1 had grade 2 acute pain after treatment (compared to 22% and 13% in the cohort, respectively).

Conclusion:

This is the first study investigating dose deviations for Ru-106 brachytherapy. Deviations of >5% in application times are rare and seem related to inconvenient removal times. Most dose deviations are not caused by deviations in application times but by tumour dimensions beyond the therapeutic range of Ru-106, and are associated with more recurrences and mild to moderate side-effects. Currently, proton irradiation is used at our center for tumours with prominence over 7mm.

Keywords: Ruthenium-106, uveal melanoma, brachytherapy