# The Impact of Edition Differences in the International Retinoblastoma Classification (IIRC vs. ICRB) on Staging and Globe Salvage Prognosis: Analysis of 642 Eyes

## TL;DR

This study compares two retinoblastoma staging systems and finds that differences in definitions affect treatment staging and eye salvage rates, suggesting the need for a unified classification.

## Contribution

The study reveals how definitional discrepancies between IIRC and ICRB impact staging and prognosis, proposing a unified classification for better consistency.

## Key findings

- The ICRB shows better discrimination for advanced tumors compared to the IIRC.
- Differences in tumor size and subretinal fluid definitions lead to stage migration and outcome variations.
- Integrating IIRC and ICRB criteria could improve prognostic precision for retinoblastoma.

## Abstract

Retinoblastoma is the most common eye cancer in children, and early diagnosis greatly improves the chance of saving the affected eye. Ophthalmologists and ocular oncology specialists use classification systems to stage the disease and estimate the likelihood of eye preservation, but two widely used systems, the International Intraocular Retinoblastoma Classification (IIRC) and the International Classification of Retinoblastoma (ICRB), define advanced disease differently. As a result, the same tumor may be assigned to different stages, which can influence treatment decisions and reported success rates. In this large single-center study of 642 eyes, we compared the IIRC and ICRB to determine how often they assign different stages and how well they predict eye salvage. We found that differences in the definitions of tumor size and subretinal fluid can lead to stage migration and variations in reported outcomes. These findings highlight the need for greater standardization to improve consistency in patient care, research reporting, and international collaboration.

Purpose: The objectives of this study were to compare the prognostic performance, staging concordance, and eye salvage prediction of the International Intraocular Retinoblastoma Classification (IIRC) and the International Classification of Retinoblastoma (ICRB), and to assess the clinical impact of definitional discrepancies between the two systems. Design: This study used retrospective, observational case series. Participants: A total of 642 eyes with intraocular retinoblastoma (Rb) that received conservative management with intent for globe salvage (2003–2024) were assessed. Methods: Clinical records and imaging were reviewed for tumor characteristics. Each eye was staged according to both IIRC and ICRB criteria. Prognostic performance for eye salvage was analyzed using odds ratios (OR), the concordance index (C-index), and likelihood ratio χ2 tests. Main Outcome Measures: The eye salvage rate and concordance between IIRC and ICRB staging were assessed. Results: The overall eye salvage rate was 73% (471/642), decreasing significantly with larger tumor size, subretinal fluid (SRF) extent, and more seeding (p < 0.0001). The globe salvage was 24% for tumors occupying >50% of the globe compared to 77% for smaller tumors, and 47% for tumors with SRF > 1 quadrant compared to 62% for tumors with SRF ≤ 1 quadrant. Under the IIRC, the salvage rates by group were 98%, 94%, 92%, 51%, and 14% (A–E); under the ICRB, 98%, 94%, 94%, 60%, and 24%. Failure odds (ORs) increased across stages from 2.8 in Group B to 276 in Group E (IIRC) and 145.2 (ICRB). Eighty-seven (14%) eyes were upstaged under the ICRB. Of these, 72 (11%) with tumors > 50% of globe volume shifted from IIRC Group D to ICRB Group E (25% salvage), and 15 (2.3%) with SRF > 3 mm shifted from IIRC Groups B/C to ICRB Group D. The ICRB showed superior discrimination (C-index = 0.824; 95% CI, 0.80250–0.84937) compared with IIRC (C-index = 0.790; 95% CI, 0.768–0.814). Conclusions: Both systems accurately predict eye salvage, but definitional variations significantly affect staging and outcome interpretation. The ICRB improves discrimination for advanced tumors by including large tumors in Group E, while the IIRC provides finer stratification in intermediate disease through SRF extent. Integrating these criteria could yield a unified, more prognostically precise classification for Rb.