Tumour location affects the incidence of cataract and retinopathy after ophthalmic plaque radiation therapy

Abstract

Aim: To examine how tumour location affects ocular morbidity after ophthalmic plaque radiotherapy for uveal melanoma.

Methods: 69 eyes were irradiated and followed for a mean 42 months. There were 23 anterior uveal melanomas and 46 were posterior to the equator. Anterior and posterior tumours had similar basal dimensions. Their mean apical heights were 4.8 mm (anterior) and 3.5 mm (posterior) which received a mean 88 Gy and 83.4 Gy respectively.

Results: Only one patient (4%) plaqued for an anterior uveal melanoma developed secondary retinopathy (cystoid macular oedema). In contrast, 24 (52%) of the posterior choroidal melanoma patients developed retinopathy (p value <0.0001). Cataract developed in 18 (86%) eyes with phakic anterior tumour compared with seven (17%) eyes with posterior tumours (p value <0.0000). No posterior nasal tumours lost more than two lines of vision though 45% developed retinopathy.

Conclusion: While plaque radiation of anterior melanomas is more likely to cause reversible vision loss secondary to cataract, treatment of posterior tumours is more likely to be associated with irreversible loss because of retinopathy. Nasal location is also protective against severe loss of vision.

Figure 1

Note the shift in radiation distribution when the plaque is either anterior or posterior to the equator. Palladium-103 plaque overlying a hypothetical 10 × 10 × 5 mm choroidal melanoma both treated to an apex dose of 8000 cGy (80 Gy).