ESTRO 2024 - Abstract Book

S1307

Clinical - Head & neck

ESTRO 2024

Tumour volume across the three MRI-scans can be observed in Figure 1. An average increase of 5% (range -23 – 22%) in tumour volume was observed between the planning MRI and the scan after treatment. Three out of nine patients showed an increase larger than 10% (Figure 2A) and one patient, with signs of resorption of an intralesional haemorrhage, showed a decrease of more than 20% (Figure 2B). A similar pattern was observed for tumour prominence, with an average increase of 0.4 mm (range -0.9 – 1.0 mm). Furthermore, a similar increase was observed between the diagnostic MRI scan and the planning MRI (19 days apart on average). This suggests that uveal melanomas may show progression in the process leading up to treatment. Clip-tumour distances showed a median decrease of 0.1±0.6 mm between the planning MRI and day of the last fraction. This decrease was larger than 1 mm for two clips in two different patients, corresponding to an increase in tumour size. For two clips of the patient who also showed a decrease in tumour volume, the clip-tumour distances increased as well. Minimal changes were observed in the week of the treatment: tumour volume decreased 3.8% on average, with one patient showing a decrease larger than 10%. This was also in the tumour prominence, which was similar for these timepoints (average increase 0.1 mm).

Figure 1: Volume change relative to planning MRI scan.