Magnetic resonance imaging for tumor restaging after chemotherapy in retinoblastoma with optic nerve invasion

Purpose: Extraocular retinoblastoma with optic nerve invasion is treated by a multimodal protocol consisting of neoadjuvant chemotherapy, enucleation, and adjuvant therapy. This study was conducted to evaluate the performance of magnetic resonance imaging (MRI) used for tumor restaging in these children after systemic chemotherapy administration.

Methods: Contrast-enhanced MRI scan of orbits and brain was performed at diagnosis and patients were treated with neoadjuvant chemotherapy. After chemotherapy, MRI scan was repeated for tumor restaging and residual post-laminar thickening and/or enhancement of the affected optic nerve, if any, was recorded. MRI findings were correlated with histopathology in enucleated specimens. The main outcome measures were specificity, sensitivity, and accuracy of MRI in predicting post-laminar invasion after neoadjuvant chemotherapy.

Results: A total of 46 eyes (46 patients) were studied. Optic nerve thickening on MRI had a sensitivity, specificity, and accuracy of 100% (95% Confidence Interval (CI): 64.6–100%), 76.9% (95% CI: 61.7–87.4%), and 80.4% (95% CI: 66.8–89.4%), respectively. Optic nerve enhancement had a sensitivity, specificity, and accuracy of 85.7% (95% CI: 48.7–97.4%), 79.5 % (95% CI: 64.5–89.2%), and 80.4% (95% CI: 66.8–89.4%), respectively. Combined thickening and enhancement of the optic nerve had a sensitivity, specificity, and accuracy of 100% (95% CI: 60.9–100%), 82.4% (95% CI: 66.5–91.7%), and 85% (95% CI: 70.9–92.9%), respectively.

Conclusion: MRI is a valuable tool for restaging of retinoblastoma and predicting residual optic nerve disease after neoadjuvant chemotherapy. Combined thickening and enhancement on MRI appeared to be a more reliable indicator of post-laminar invasion as compared to thickening or enhancement alone.