Multi-drug resistant protein expression in retinoblastoma in primary enucleated eyes versus eyes enucleated after failure of conservative treatment

Abstract

Retinoblastoma remains an important tumor of childhood with a significant effect on both vision and life of the patient. After introduction of systemic chemotherapy as a treatment modality, many eyes have been saved from enucleation. Unfortunately, many tumors resist chemotherapeutic agents necessitating enucleation at the end. Why some tumors respond to chemotherapy and some do not remains an important question to be answered. A hypothesis was suggested that multidrug resistant proteins are responsible, totally or in part, for tumor resistance. We tried to verify this hypothesis in this study. We tried to find whether tumors which escaped chemotherapeutic agents showed higher expression of these agents. We also tried to know whether expression was related to age, sex or any of the histopathological features. This study did not demonstrate a clear cut difference in expression of MDR1 between primary enucleated eyes and secondary enucleated eyes. As the P-value for this dfeerence was 0.068, though being nonsignificant, the value is low enough to indicate a trend for more MDR1 expression in resistant cases. We would assume that this value may reach significance if the sample size were to be increased. 111 On the other hand, expression of MDR1 was clearly not related to age at presentation, age at enucleation, presentation-enucleation interval, gender, tumor laterality or histopathological features as tumor differentiation, optic nerve invasion or choroidal infiltration. A remark of much significance is the delayed age of presentation of retinoblastoma compared to that documented in international literature. This mandates taking some measures for early detection of the tumor and early treatment of it in its early stages such as increasing public awareness, implementing screening programs and increasing well-equipped ophthalmic clinincs in distant and rural areas. Another equally important remark is the high rate of optic nerve invasion in tumors with secondary enucleation. This most probably reflects a delayed decision making regarding enucleation in the proper time. A strict adherence to criteria for enucleation is recommended with timely intervention.