Retinoblastoma Morphology after Local Chemotherapy

Purpose. Determine the nature of tumor regression and possible complications associated with the retinotoxic effect of melphalan and carboplatin with local chemotherapy.Methods. A histological analysis of 19 enucleated eyes from 19 patients with retinoblastoma was performed after combined organ-preserving treatment, including systemic chemotherapy and local chemotherapy in various doses. The enucleated eyes were fixed in 10 % formalin and processed routinely for histological examination.Results. Significant changes in the tumor tissue such as tumor regression associated with the destruction of the tumor tissue and its replacement with fibrous tissue, glia proliferation, and the formation of petrificates were revealed. Complete regression of the tumor was detected in 3 out of 19 eyes, partial in 13 eyes. There were no signs of regression in 3 eyes. Tumor invasion into the choroid was found in 5 cases, into the anterior sector — in 3 cases, into the optic nerve — in 3 cases. The retrobulbar tumor was presented in 1 case. Retinotoxic complications revealed. Hemorrhagic changes associated with focal necrosis of the central retinal vessels (n = 4), destructive changes in retinal pigment epithelium (RPE; n = 10) associated with the accumulation of melphalan in RPE leading to atrophic processes in the retina. Complications in the form of secondary glaucoma, severe fibrosis and retinal detachment, despite the complete resorption of the tumor, led not only to loss of vision, but also hindered visualization of the fundus and substantiated the need for enucleation in 3 cases. In other cases, enucleation was performed due to continued tumor growth (n = 16) or progression during treatment (n = 3).Conclusions. Retinoblastoma can be controlled with local chemotherapy. However, clinical and morphological examinations of enucleated eyes revealed and confirmed, along with tumor resorption, intraocular complications as a result of the toxic effect of the drugs and the presence of active tumor tissue to varying degrees of therapeutic pathomorphism, which can be explained by the resistance of RB to these drugs. Thus, a further search is needed for drugs that destroy the tumor and minimize the retinotoxic effect.