Treatment Outcomes and Definition Inconsistencies in High-Risk Unilateral Retinoblastoma

Purpose

To compare the clinical outcomes of children with unilateral retinoblastoma (Rb) and high-risk histopathology features (HRHF) following upfront enucleation with/without adjuvant chemotherapy, and investigate cases locally considered non-HRHF but converted to a standardized HRHF definition.

Design

Retrospective multinational clinical cohort study.

Methods

Children with Rb who presented to 21 centers from 12 countries between 2011-2020, and underwent primary enucleation were recruited. Centers retrieved clinical data and were asked to report detailed histopathology findings, as well as indicate cases defined locally as high-risk. For analysis, only unilateral cases with standardized HRHF, defined as retrolaminar optic nerve invasion, massive choroidal invasion, scleral invasion, anterior-segment involvement, and/or combined nonmassive choroidal and prelaminar/laminar optic nerve invasion, were included. Main outcome measures included orbital tumor recurrence, systemic metastasis, survival and number, and outcome of cases converted to standardized HRHF.

Results

A total of 600 children presenting to 14 centers in 9 countries were included. Of these, 505 (84.2%) were considered locally as HRHF and received adjuvant chemotherapy. After a median follow-up period of 39.2 ± 1.6 months (range: 0.8-60.0 months), 36 (6.0%) had orbital tumor recurrence, 49 (8.2%) metastasis, and 72 (12.0%) children died. Children not receiving adjuvant chemotherapy were at significantly increased risk of orbital tumor recurrence, metastasis, and death (P ≤ .002). Of the study children, 63/600 (10.5%) were considered locally non-HRHF, but converted to standardized HRHF and included in the analysis. Of these, 6/63 (9.5%) had orbital tumor recurrence, 5/63 (7.9%) metastasis, and 6/63 (9.5%) children died. Isolated minor choroidal invasion with prelaminar/laminar optic nerve invasion was reported in 114 (19.0%) children, but considered locally as HRHF only in 68/114 (59.6%). Of these, 6/114 (5.3%) children developed metastasis and subsequently died, yielding a number needed to treat of 15.

Conclusion

Based on this multinational cohort of children with Rb, we recommend the use of adjuvant chemotherapy following upfront enucleation and diagnosis of HRHF. Variation exists worldwide among centers when defining HRHF, resulting in adverse patient outcomes, warranting standardization.