A non-comparative case observation study estimated the feasibility of brachytherapy for retinoblastoma with a newly designed ruthenium-106 plaque (label: CXS) with an 8-mm diameter of the irradiation zone.
Methods: The new CXS plaque was used between 2001 and 2003 for brachytherapy of 13 retinoblastomas. Indications were recurrences after preceding local treatment or endophytic retinoblastoma with an impending vitreous tumour cell seeding. The prescribed radiation dose at the apex was 88 Gy (NIST-calibrated dosimetry).
Results: The mean age at brachytherapy was 1.2 years (standard deviation, SD: 1.1 years), and the mean follow-up was 1.7 years (SD: 0.6 years). The treated tumours had a mean diameter of 2.3 mm (SD: 0.7 mm) and a mean height of 1.5 mm (SD: 0.6 mm) with a mean distance to the optic disc of 9.9 mm (SD: 2.2 mm). The mean duration of irradiation was 29.3 h (SD: 9.9 h) with a mean dose at the sclera of 213 Gy (SD: 80 Gy). Surgery was uneventful in all cases. Complete regression developed after 3.1 months (SD: 2.8 months) in all cases without a recurrence or a progression of the vitreous tumour cell seeding. The eyes developed no further side-effects besides a temporary circumscribed intra-ocular haemorrhage that emerged from the regressive tumour remnants.
Conclusion: Brachytherapy with the CXS plaque seems to be a safe and reliable treatment option for small-sized retinoblastoma when laser or cryocoagulation failed to control the tumour growth or for small retinoblastoma with an incipient local tumour cell seeding on the tumour surface.