Quantitative assessment of choroidal melanoma response to gamma knife radiosurgery (GKR) treatment with contrast-enhanced ultrasound (CEUS): preliminary results

Abstract

 

Purpose

 

To evaluate tumor vascularization changes in patients with choroidal melanoma before and after gamma knife radiosurgery (GKR) treatment with contrast-enhanced ultrasound (CEUS).

 

Methods

 

Ten consecutive patients diagnosed with choroidal melanoma and treated with GKR were enrolled. A complete ophthalmological evaluation and CEUS (SonoVue, Bracco) with iU-22 ATL (Philips) and 5-9 MHz linear probe were performed before treatment and 3, 6 and 12 months after GKR. In each examination, two main tumor diameters and different quantitative parameters related both to tumor blood volume and blood flow (area under the curve in the wash-in phase - WiAUC, wash-in perfusion index - WiPI, peak enhancement - PE, wash-in rate - WiR) were calculated using a dedicated imaging processing software and compared using the Wilcoxon analysis.

 

Results

 

Subjects involved included 7 males and 3 females with a mean age of 66.4 years (range: 45-82 years). All melanoma lesions were located in the choroid; scleral infiltration did not occur in any case. Mean tumor thickness at baseline, 3, 6 and 12 months after GKR were 8.3mm, 7.4mm , 6.6mm and 5.8mm respectively. As expected, a significant reduction in tumor thickness occurred 6 months after GKR (20.5% reduction, p=0.031) and 12 months after GKR (24.2% reduction, p=0.024). Regarding changes in tumor vascularization, comparison between PE, WiR and WiPI before and 6 months after GKR showed significant reduction in all patients (p=0.018, p=0.028, p=0.028 respectively). At 12 months after GKR PE, WiR, WiPI and WiAUC values resulted to be statistically different from the respective parameters at baseline in all patients as well (p=0.028, p=0.028, p=0.043, p=0.028).

 

Conclusions

 

This preliminary study demonstrated the feasibility of perfusion analysis of choroidal melanoma with CEUS. Tumor thickness at 6 and 12 months after GKR showed a significant reduction, indicating local tumor control. Accordingly, a reduction in parameters descriptive of intralesional vascularization at 6 and 12 months after GKR may objectively describe a significant depletion in tumor blood vessels following radiation therapy.

 

 

Screenshot of the software in 4 quadrants. A specific region of interest is outlined and quantitative vascularization parameters are subsequently assessed.

 

Keywords: 589 melanoma • 671 radiation therapy • 552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)