New Zealand experience of I125 brachytherapy for choroidal melanoma

To examine patient survival, visual function and complications in all patients with choroidal melanoma treated with I125 brachytherapy between 1995 and 2003 at the authors' institution. To compare the results from their institution with those from international series.

Data were collected on 92 consecutive patients. Dosimetry was calculated for the lens, fovea, optic nerve and tumour apex. Follow-up status of each patient domiciled outside the treatment centre was analysed from a postal questionnaire.

Average pretreatment tumour dimensions were 3.9 mm (thickness) and 15.2 mm (diameter). Complete follow-up data were available on 92% of patients. Regression of tumour occurred in 88% of cases. Five enucleations were performed. There were five melanoma-related deaths. Visual acuity remained >6/12 in 35% of patients and >6/60 in 51% of patients. The most frequently observed complication was radiation retinopathy (maculopathy 23%, peripheral retinopathy 17%). Radiation cataract was seen in 11% and optic neuropathy in 10%. Dose of more than 90 Gy to the macula gave a 63% chance of developing maculopathy (P < 0.01). A tumour larger than 4 mm significantly increased the risk of developing radiation maculopathy (P = 0.003). Development of radiation cataract was dose-related; >25 Gy to the lens gave a 44% risk of cataract development (P < 0.001). For tumours less than 4 mm from the disc margin there was a 50% risk of optic neuropathy (P < 0.001).

Patient outcomes following brachytherapy were excellent with a high percentage of patients retaining mobility vision. Development of complications was related to the tumour location and dose to non-tumour structures.