Microcirculation patterns in indocyanine green angiography and the results of plaque therapy in choroidal melanoma

Introduction
To determine the effect of radioactive plaque therapy on blood vessel behaviour in choroidal melanomas using indocyanine green (ICG) angiography.

Material and methods
Fifty-five patients with choroidal melanoma were studied. Ruthenium-106 plaques were used in 30 eyes, in 11 the “sandwich method” (Ruthenium-106 plaque with transpupillary thermotherapy), was applied and 14 tumours were treated with Iodine-125. In all cases ICG angiography was performed prior to treatment and 12 months after, and at different time afterwards. Baseline tumour microcirculation patterns (MCPs) were studied prior to treatment and post-treatment blood vessels changes were evaluated. Total follow-up period ranged from 14-22 months (mean: 16 months).

Results
Pre-treatment ICG angiography revealed complex MCPs, combining parallel with cross-linking, arcs with branching, loops and networks patterns in 23 (41.8%) and non-complex MCPs, including straight, parallel without cross-linking and arcs without branching patterns in 32 (58.2%) melanomas. Twelve months after treatment, 38 tumours (69.1%) showed a significant changes in their MCPs. The mean ultrasonographic regression rate in tumours with complex MCPs was 57.4% as opposed to 36.2% in the group with non-complex MCPs (p = 0.01). No statistically significant correlation in the height regression rate was found among the various methods of therapy, however a significant difference between the type of therapy and MCPs changes was observed (p<0.001). Melanomas treated with Ruthenium-106 and TTT demonstrated slight or no MCPs changes, while tumours treated with Ruthenium-106 and Iodine-125 plaques alone showed a significant MCPs changes (p<0.001). The statistical analysis showed the correlation between the type of baseline MCPs and the degree of their changes after treatment (p<0.001). Tumours with networks, loops, arcs with branching and parallel with crossing showed an increased regression as compared to other MCPs. Twelve patients whose tumours contained complex MCPs developed metastatic disease.

Conclusions
This study suggests that the response of choroidal melanoma to irradiation is related to MCPs as identified by ICG angiography; the presence of complex MCPs is associated with a high regression rate after plaque therapy and a high risk of development of systemic metastatic disease.