Background: Radioactive episcleral plaque brachytherapy is a treatment method for selected retinoblastomas. The authors have used this technique since 1976 as both a primary and a secondary treatment method after other methods failed to achieve tumor control.
Methods: A review of the records of 400 consecutive children with retinoblastoma showed that solitary plaque radiotherapy was used as a method of management in 103 cases. The authors' overall experience was evaluated, and the results between primary and secondary plaque therapies were compared in these 103 cases.
Results: Of the 103 tumors, the mean basal diameter was 7 mm, and the mean thickness was 4 mm. Overlying vitreous seeds were clinically apparent in 50 cases (48%). The mean proximity of the tumor margin to the optic disc margin was 6 mm and to the foveola was 6 mm. The mean follow-up period was 40 months. In 89 cases (86%), the tumor was controlled by one plaque application, whereas in 13 cases (13%), tumor recurrence after initial tumor shrinkage necessitated subsequent treatment. Final visual outcome was good in 63 cases (62%), poor in 30 (29%), enucleation in 9 (9%), and unknown in 1 case. The poor vision was due to foveal retinoblastoma (with or without amblyopia) in 25 cases (83%). Eight of the nine enucleated eyes were treated initially with external beam radiotherapy then later with plaque radiotherapy. In 31 cases (30%), plaque radiotherapy was used as a primary treatment to the tumor, while in 72 cases (70%), it was a secondary form of management after failure of other methods to control the tumor. Statistical analysis showed that tumors treated with plaque radiotherapy as a primary measure were more likely to be larger in in base (P = 0.01) and thickness (P = 0.01) than secondary treated tumors. The secondary treated retinoblastomas were more likely to have vitreous seeds (P = 0.02) than the primary treated tumors. The rate of tumor control and patient survival was similar between the two groups.
Conclusion: Plaque radiotherapy is very effective in treating selected retinoblastomas with a high rate of tumor control and patient survival. It can be used successfully as a primary or a secondary treatment for tumors that have not been adequately controlled by other therapeutic methods.