Disseminated retinoblastoma successfully treated with myeloablative chemotherapy - implication for molecular detection of minimal residual disease

A useful marker for detecting minimal residual disease (MRD) has not been e stablished yet in retinoblastoma. We assessed neuroendocrine protein gene p roduct 9.5 (PGP9.5) expression, one of the markers for detecting MRD in neu roblastoma, in a patient with disseminated retinoblastoma, A 3-year-old boy with disseminated retinoblastoma in multiple bones and marrow was referred to our hospital. He received intensive treatment and has maintained CR for 48 months following myeloablative chemotherapy with hematopoietic stem cel l transplantation (SCT), PGP9.5 expression was serially assessed by RT-PCR in peripheral blood mononuclear cells (PBMC), bone marrow cells (BMC) and m obilized peripheral blood stem cells (PBSC), Initially, his BMC consisted o f 96% tumor cells which were proved to express PGP9.5 by RT-PCR, Moreover, PBMC were found to be positive for PGP9.5 indicating the presence of tumor cells in the peripheral blood. After intensive chemotherapy, PGP9.5 express ion became negative in both PBMC and BMC, Prior to SCT, PBSC and BMC transp lants were confirmed negative for PGP9.5 expression, It is suggested that P GP9.5 expression is a useful marker for evaluating therapeutic effects as w ell as detecting MRD in retinoblastoma.