Abstract
PURPOSE: To determine the significance of large tumour size as a criteria for classifying advanced intraocular retinoblastoma, analysing rates of globe survival and high-risk (HE) histopathologic features. METHODS: Retrospective chart review of 212 eyes diagnosed with Group D (111 eyes) or Group E (101 eyes) retinoblastoma in at least one eye from January 1, 2006 to December 31, 2016 using the Los Angeles (LA) Classification System (no tumour size criteria for Group E). The 111 Group D tumours were then reclassified to Group E using 10, 12, 14, 16, 18 mm tumour size criteria, as determined by ultrasound or magnetic resonance imaging dimensions. RESULTS: For eyes in the original LA classification, 66.7% of Group D and 10.5% of Group E eyes undergoing globe preservation therapy avoided enucleation or radiotherapy (p < 0.0001; median follow-up of 33.0 months). In the LA classification, 8.5% of Group D and 26.3% of Group E enucleated globes had HE histopathologic features (p = 0.0065). When Group D eyes with tumours meeting the size criteria were reclassified to Group E, 65.7-74.4% of Group D and 16.1-36.7% of Group E eyes avoided enucleation or radiotherapy. Applying the tumour size criteria, 0-10.9% of Group D and 20.7-23.8% of Group E eyes had HE histopathologic features. CONCLUSION: Our retrospective analysis suggests that a large tumour size criteria for Group E retinoblastoma have no clinical basis, given that the LA classification system provided the greatest separation in globe salvage rates between Group D and E eyes. The LA classification system was also able to show a statistically significant difference in the rates of HE histopathologic features between Group D and E eyes. To avoid discrepancies in the literature, we recommend that centres use one uniform system for classifying advanced intraocular retinoblastoma.