Choroidal melanoma responses after brachytherapy treatment

[Conservative treatment of choroidal melanoma using iodine-125 brachytherapy, technique and preliminary analysis of 78 patients]

PURPOSE

Iodine 125 curietherapy is one of the conservative treatments of uveal melanoma. The technique used to achieve these results was simplified through the physical characteristics of the radioelement and the optimized-dosimetry program employed.

PATIENTS AND METHODS

78 patients with choroidal melanoma were treated with iodine 125. About 100 Gy were delivered to the superior pole of the tumour. The minimal length of follow-up was 17 months and the average, 67 months.

RESULTS

There was 88% local control, leading to lowered visual acuity in 76% of the cases. Radiation retinopathy, directly related to proximity to the macula, is the principle etiology. Seven patients died of hepatic metastasis, five patients were enucleated. Four patients were further treated with protontherapy to make up for noncontrol locally.

CONCLUSION

One dose of 100 Gy to the superior pole of the tumor seemed to lead to good local control, with the exception of complications related to proximity to the macula and the optic nerve. In this attempt to optimize irradiation, the time lapse between any benefit in local control derived from irradiation and posttherapeutic complications observed remains insufficient to evaluate any relationship.

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

PURPOSE

The value of the new tumour-seeking agent technetium-99m (V) dimercaptosuccinic acid (99mTc (V) DMSA), is assessed by the visualization of choroidal melanoma before and after iodine-125 episcleral plaque brachytherapy.

METHODS

A prospective study was conducted on 12 consecutive patients with choroidal melanoma that was to be treated with plaque brachytherapy. The pre-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 scintigraphy and single-photon emission computed tomography using 99mTc (V) DMSA 2 days before treatment and 8 months following plaque removal. The calculated tumour to background ratios of these two tests were compared.

RESULTS

The pre-operative tumour to background ratio was 1.8+/-0.4 and all tumours could be correctly identified. At the time of postoperative imaging, all melanomas showed varying degrees of regression. The mean tumour height 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 significant (P = 0.002).

CONCLUSIONS

Technetium-99m (V) DMSA scintigraphy can accurately detect choroidal melanoma and document tumour response following episcleral radioactive plaque therapy. As such, this test can be an alternative ancillary investigative tool in the rare event of opaque media or diagnostic uncertainty.