ESTRO 2024 - Abstract Book

S298

Brachytherapy - Head & neck, skin, eye

ESTRO 2024

the optic disk were not eligible. Ruthenium plaque type was chosen based on tumour diameter and localization. Radiation dose was calculated based on tumour prominence with a prescribed dose of 130 Gy to the tumour apex, standardised to 100 Gy per 24 hours. Adjustments to the prescribed apex dose were only made when scleral dose was below 300 Gy or over 1000-1200 Gy. Time to event data were analysed using Kaplan-Meier’s methodology. We investigated differences in visual acuity between different timepoints and eyes with the Wilcoxon signed-rank test. Hierarchical clustering was used to visualize trends in visual acuity decline in the first five years of follow-up after imputation of missing visual acuity values using linear interpolation. 172 patients were included in this study. Clinical characteristics of the cohort are described in table 1. 51% of the tumours were centrally located, and 23% of tumours were within one disk diameter from the optic disk. Median follow-up was 9.8 years. Five-year survival probability was 82%, risk of metastases after 5 years was 14%, while risk of local recurrence and secondary enucleation were 7% and 3%, respectively. Five enucleations were performed for local recurrence, one for treatment toxicity. Median baseline visual acuity (Snellen scale) was 0.9 (range 0.0-1.6) in the ipsilateral and 1.0 (range 0.0-1.5) in the contralateral eye. Visual acuity of the ipsilateral eye at last follow-up had significantly decreased (median 0.5, range 0.0-1.5, p<0.001). Visual acuity change over time in the ipsilateral eye was significantly bigger than the normal visual acuity change in the contralateral eye, which was not irradiated(p<0.001). Figure 1 shows visual impairment according to the ICD-11 classification at baseline and over five years after treatment. At five years, 49% of patients had no visual impairment (visual acuity according to Snellen ≥0.5) while 31% had severe visual impairment (visual acuity <0.1). Figure 2 shows the relation between visual acuity change and tumour localisation. Patients with a low baseline visual acuity retained similar visual acuity or experienced a decline therein. In patients with centrally located tumours, this treatment method was less often vision-sparing than in others; 52% had severe visual impairment at end of follow-up, in contrast to 16 % in those with midperipherally, and 24% in those with peripherally located tumours. Results:

Age (years)

64 (20-88) 91 (53%) 95 (55%)

Sex (female)

Affected eye (right)

Tumour prominence (mm) Tumour diameter (mm) T-stage (AJCC 8 th ed.)

3.9 (1.8-8.1)

11.8 (3.6-19.0)

T1

43 (25%)

T2

95 (56%)

T3

33 (19%)

Affected structure

Choroid

165 (96%)

Ciliary body

16 (9%)

Iris

10 (6%)