Treatment of non-resectable malignant iris tumours with custom designed plaque radiotherapy

Plaque radiotherapy is the most common method of managing posterior uveal melanoma but its use for iris melanoma and iris metastases has not yet been evaluated.

Fourteen patients with non-resectable iris melanoma and four with iris metastasis were treated with plaque radiotherapy. The tumour response to treatment and the local side effects of the radioactive plaque were evaluated.

In the iris melanoma group over a mean follow up of 26 (range 6-75) months, the tumour regressed in 13 of the 14 patients (93%) and recurred as diffuse seeding in one patient (7%). Despite large doses of radiation given transcorneally, the cornea developed epitheliopathy, abrasion, and oedema in only one case each. The major radiation side effects were localised iris vasculopathy without glaucoma in two cases, posterior synechiae in five cases, and cataract in six cases. In the iris metastasis group, tumour regression was observed in all four patients (100%) and radiation side effects were not evident over the relatively short mean follow up period of 8 (range 4-9) months. All of the 14 patients with irradiated iris melanoma have remained systemically healthy without metastasis while three of the four patients with irradiated iris metastases have died of metastases from the primary neoplasm.

Custom designed plaque radiotherapy appears to be an effective alternative method of controlling non-resectable diffuse iris melanoma and solitary iris metastasis and has relatively few side effects.