Technetium-99m (V) dimercaptosuccinic acid uptake by choroidal melanoma before and after iodine-125 brachytherapy

Purpose: The value of the new tumour-seeking agent tecilnetium-99m (V) dime rcaptosuccinic acid (Tc-99m (V) DMSA), is assessed by the visualization of choroidal melanoma before and after iodine-125 episcleral plaque brachyther apy. Methods: A prospective study was conducted on 12 consecutive patients with choroidal melanoma that was to be treated with plaque brachytherapy. The pr e-operative mean (+/- SD) maximal tumour basal diameter was 12.9 +/- 2.9 mm and the mean tumour height was 8.2 +/- 2.9 mm. Each patient had planar sci ntigraphy and single-photon emission computed tomography using 99mTc (V) DM SA 2 days before treatment and 8 months following plaque removal. The calcu lated tumour to background ratios of these two tests were compared. Results: The pre-operative tumour to background ratio was 1.8 +/- 0.4 and a ll tumours could be correctly identified. At the lime of postoperative imag ing, ail melanomas showed varying degrees of regression. The mean tumour he ight was 4.4 +/- 2.1 mm, The tumour to background ratio was 1.4 +/- 0.3,The difference between the two scintigraphic results was statistically signifi cant (P = 0.002). Conclusions: Technetium-99m (V) DMSA scintigraphy can accurately detect cho roidal melanoma and document tumour response following episcleral radioacti ve plaque therapy. As such. this test can be an alternative ancillary rare event of opaque media or investigative tool in the diagnostic uncertainty.