1.P.07 OSTEOSARCOMA IN RETINOBLASTOMA SURVIVORS: MOLECULAR ANALYSIS AND RESULTS OF MULTIMODAL MANAGEMENT

Abstract

Osteosarcoma is the most common second malignancy seen in retinoblastoma survivors. Risk of developing osteosarcoma in this group is estimated approximately 500 times higher than the general population. Prognosis in this setting has been reported significantly worse than conventional osteosarcoma despite multimodal management. Purpose of this study was to evaluate clinical features, molecular aspects and outcome of treatment in this subgroup of osteosarcoma patients.

Between 1985 and 2004, from a total of about 1100 osteosarcomas, 7 survivors of retinoblastoma developing high-grade osteosarcoma as second malignancy presented at the authors’ Institution. Retrospective study was undertaken to analyze presentation, tissue expression of RB1, P53, PGP and DHFR, treatment and outcome of both retinoblastoma and osteosarcoma.

Retinoblastoma was bilateral in 5 cases and unilateral in two. All the patients had been treated with a combination of surgery +/− chemotherapy +/− radiation.

None of them had evidence of retinoblastoma at the time of second malignancy diagnosis. Average age at diagnosis of osteosarcoma was 14 years (9–17 years), mean interval between the two malignancies was 155 months. All the osteosarcomas were in the appendicular skeleton, all but one around the knee. Molecular analysis showed defective RB1 gene in all cases All the seven patients received contemporary multimodal management for osteosarcoma. All but one patient died of osteosarcoma within 30 months from diagnosis. The living patient had local recurrence 9 years after limb salvage and is currently disease free following amputation.

Prognosis of osteosarcoma in retinoblastoma patients remains poor as compared to conventional high grade osteosarcoma despite multimodal management. No obvious correlation was found between poor prognosis and P53, PGP and DHFR expression.