Figure 6. Different classification schemes for intraocular retinoblastoma confound comparison of outcomes.

The features listed determine the overall classification, ranging from small tumours not threatening vision (“Group A”) to tumours clinically noted to have features suggesting potential spread outside the eye (“Group E”). Most importantly, size of tumour alone does not make an eye dangerous by Murphree,⁷⁸ Children’s Oncology Group (COG),⁸¹ or TNM classification;⁸² but any eye with tumour >50% of eye volume is E (advanced-stage disease) by Shields classification.⁷⁹ The consequence is widespread confusion in the literature undermining clinical research, since studies using the different classifications cannot be compared. The red boxes indicate the critical differences between the different classifications.