Combined intravitreal and subconjunctival carboplatin for retinoblastoma with vitreous seeds

To describe the technique of intravitreal chemotherapy preceded by subconjunctival chemotherapy for the treatment of vitreous seeds in advanced stage retinoblastoma.

This non-comparative interventional case series retrospectively reviewed the medical records and postenucleation histopathological findings of two patients who presented within weeks of each other with bilateral retinoblastoma, Reese-Ellsworth (R-E) stage Vb in the worse eye. Both patients had failed systemic chemotherapy prior to receiving a single treatment of 0.5 ml (5 mg per 0.5 ml) of subconjunctival carboplatin, through which 0.05 ml (3 mcg per 0.05 ml) of carboplatin was injected into the vitreous (Case 2 received 0.1 ml of intravitreal carboplatin). The subconjunctival chemotherapy was given to reduce the risk of orbital tumour seeding following intravitreal injection. Following enucleation, ocular toxicity and the presence or absence of viable tumour cells at the intravitreal injection site were recorded.

Histopathological examination did not reveal patency of the pars plana intravitreal penetration site in either case at 6 weeks post-treatment nor was malignant seeding detected in the area of injection. Examination of the two enucleated eyes did not demonstrate structural toxicity to the cornea, anterior segment, iris or retina. Additionally, both cases were followed for over 37 months post-treatment, without the occurrence of orbital malignancy.

Injecting a bleb of subconjunctival chemotherapy prior to intravitreal drug delivery appeared to mitigate the risk of orbital tumour seeding in two patients with advanced stage retinoblastoma. Incorporating this technique may allow further investigation of intravitreal chemotherapy for the treatment of vitreous seeds in retinoblastoma.