MR‐based follow‐up after brachytherapy and proton beam therapy in uveal melanoma

Abstract

AbstractPurpose: Comparison of Magnetic Resonance Imaging (MRI) with conventional ultrasound for the follow‐up in Uveal Melanoma (UM) patients treated with brachytherapy or proton beam therapy (PBT).Methods: 26 UM patients were scanned before, 3, 6 and 12 months after ruthenium brachytherapy (n = 13) or PBT (n = 13) at 3Tesla MRI. Tumour prominence measurements were compared between MRI and ultrasound. On Perfusion weighted MR‐imaging (PWI), the relative enhancement and outflow at 2 min after peak were assessed. Treatment response was defined as a reduction of ≥0.6 mm prominence and/or ≥5% perfusion outflow was achieved.Results: Pretreatment prominences were comparable on MR and ultrasound (mean absolute difference 0.49 ± 0.46 mm), larger differences were observed at 3 and 6 months post treatment (0.88 ± 0.86 mm and 0.74 ± 0.72 mm, respectively). At 12 months post treatment, the difference was reduced to 0.55 ± 0.33 mm. Pretreatment, 76% of the UM showed a washout perfusion curve. The pretreatment average enhancement and outflow were 98% (SD:49%) and 31% (SD: 25%) respectively. At 3 months post treatment tumours showed 41% less outflow on average with more favourable perfusion curves (e.g. 68% showed a persistent or plateau curve). At 6 and 12 months post treatment, tumours continued to show less outflow (respectively, −47% and −38%) and more favourable perfusion curves (respectively, 79% and 76% with either persistent or plateau curves). These, generally favourable, perfusion changes were also observed when no reduction in prominence was yet apparent, which is why treatment response was more frequently detected on MRI as opposed to ultrasound. For example, at 3 months post treatment >80% of patients were already detected on MRI versus 46% on ultrasound.Conclusions: MRI is beneficial for the follow‐up of UM patients, especially for PBT treated patients as these generally take longer before a reduction in prominence can be observed.