Background Published findings on MRI results in retinoblastoma patients treated with neoadjuvant chemotherapy (NACT) are lacking. The present study evaluates the role of MRI in International Retinoblastoma Staging System (IRSS) stage III retinoblastoma treated with NACT.

Methods 28 consecutive IRSS stage III retinoblastoma patients underwent MRI at baseline and after three cycles of NACT prior to enucleation. MRI films were reviewed retrospectively by an ophthalmic radiologist who was masked to patient outcome. Optic nerves were staged based on their thickness, contrast enhancement and length of involvement on MRI. Response evaluation criteria were based on optic nerve staging and changes in the size of the orbital mass on MRI after NACT.

Results The proposed staging at baseline and after NACT was able to predict event-free-survival (EFS) (p=0.005 and p <0.001, respectively) and overall survival (OS) (p=0.002 and p=0.001, respectively) using the log-rank test for trends. Patients with complete or partial response according to the proposed response evaluation criteria had significantly better EFS (p<0.001) and OS (p=0.024) than those who had stable or progressive disease.

Conclusions The proposed MRI based optic nerve staging system and response evaluation criteria were able to predict EFS and OS at baseline and after NACT.