Abstract
The aim of this study was to assess retinal toxicity in a rabbit model after carboplatin delivered as repeated transcorneal intravitreal injection, in order to determine the highest possible safe dose for use in human retinoblastoma "seeding" tumor chemotherapy. We used six albino rabbits in an in vivo experiment and injected 0.008 mg of carboplatin intravitreally (iv) 4 times at two-week intervals. 0.08 mL saline was injected into the left eye. We recorded electroretinograms (ERGs) before the first carboplatin injection and after the fourth injection. Platinum concentration was measured 1 h after the fifth additional injection. We found reduced dark-adapted b-wave amplitudes and, light-adapted b-wave and a-wave amplitudes. The differences between right and left eyes was significant but we found no histopathologic retinal changes. 0.008 mg of carboplatin is probably the highest possible safe dose for the treatment of retinoblastoma patients. Questionable is direct extrapolation of retinal toxicity from the rabbit eye model to the human eye.
Highlights
Retinoblastoma is a childhood cancer arising from immature retinal cells in one or both eyes
Chemo therapeutics are used in treatment but vitreous seeding is a serious limiting factor in retinoblastoma therapy
No serious com plications have been found to date but tumor dissemi nation in human retinoblastoma was demonstrated by subsequent fine needle biopsy or pars plana vitrectomy[6]
Summary
Retinoblastoma is a childhood cancer arising from immature retinal cells in one or both eyes. Some are too complex for clinical practice or vitreous concentrations of chemo therapeutic do not reach effective levels and are unstable[1] Another described treatment is intravitreal transscleral injection of chemotherapeutic agent[4,5]. Some physicians used a more difficult approach through the limbus, anterior chamber and peripheral iris for fine needle aspiration biopsy to avoid seeding tumor cells into orbital tissues[7,8,9] This approach was used in this experiment. We assessed possible retinal changes after transcorneal intravitreal carboplatin injection which would preclude its use in clinical practice. The aim of this study was to assess retinal toxicity in a rabbit model after carboplatin delivered as repeated transcorneal intravitreal injection, in order to determine the highest possible safe dose for use in human retinoblastoma “seeding” tumor chemotherapy. Questionable is direct extrapolation of retinal toxicity from the rabbit eye model to the human eye
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