Regression patterns of choroidal melanoma: After palladium-103 (¹⁰³Pd) plaque brachytherapy

To describe the patterns of regression of choroidal melanoma after treatment with plaque brachytherapy.

Retrospective interventional case series including 170 consecutive patients treated with ¹⁰³Pd eye plaque radiation for choroidal melanoma. Outcome measures were changes in tumor thickness, surface characteristics, tumor vascularity, ultrasonography, fluorescein angiography, optical coherence tomography, and histopathology.

The mean initial tumor thickness was 3.9 mm (median 2.8 mm; range 2-11.3 mm) that decreased to 1.7 mm (median 1.2 mm; range 0-7.1 mm) after plaque brachytherapy. On imaging, tumors were pigmented in 51% ( n = 86/170), amelanotic in 10% ( n = 17/170), and variably pigmented in 39% ( n = 67/170). Tumor pigmentation increased in 64% ( n = 106/166), decreased in 18% ( n = 30/166), and was unchanged in 18% ( n = 30/166). Of the 120 that demonstrated intrinsic vascularity, 10% ( n = 12/120) had decreased tumor-related vascularity and 90% ( n = 108/120) showed complete resolution. Subretinal fluid was present in 34% ( n = 58/170) of eyes at presentation. Of them, 15% (9; n = 9/58) had persistent SRF at last follow-up. On ultrasound imaging, 88% ( n = 149/170) tumors presented with low to moderate internal reflectivity of which 61% ( n = 91/149) showed increased reflectivity on regression. We noted a crescendo-decrescendo fluctuation in the presence of orange pigment lipofuscin along with complete resolution of drusenoid retinal pigment epithelial detachments. In the entire series of 170 patients, there was 0.5% (1) failure of local control, 2% (4) secondary enucleations, and 6% (10) patients developing metastasis.

Findings related to choroidal melanoma regression after ¹⁰³Pd plaque brachytherapy included decreased intrinsic tumor vascularity, decreased tumor-related subretinal fluid, increased pigmentation, specific changes in orange pigment lipofuscin and resolution of drusenoid retinal pigment epithelial detachments, as well as decreased tumor thickness with an increase in internal reflectivity on ultrasound.