Histopathologic risk factors in retinoblastoma: a retrospective study of 172 patients treated in a single institution.

BACKGROUND: Microscopic extrascleral involvement and involvement of optic nerve resection line are accepted risk factors for orbital and/or metastatic disease from retinoblastoma. Conversely, choroidal and retrolaminar optic nerve involvement are questionable risk factors. The aim of this retrospective study was to define the histopathologic risk factors for orbital and/or metastatic disease in patients treated by first-line enucleation.
METHODS: Histopathologic review of 172 evaluable patients treated at Institut Curie between 1977 and 1990 determined the degree of choroidal (minimal or massive), scleral (intra- or extrascleral), optic nerve (prelaminar, retrolaminar with or without resection line involvement), and anterior chamber invasion. The degree of differentiation was also analyzed. The log rank test was used for univariate analysis and the Cox regression model was used for multivariate analysis. RESULTS. Eighty-seven percent of the 172 patients were disease free at 3 years. Twenty-three patients developed retinoblastoma recurrence. The disease-free survival was significantly different among the five subgroups of choroidal or scleral invasion (P = 3 x 10(-3). The differences among the four subgroups of optic nerve invasion were also significant (P = 10(-4)). Classical factors were confirmed in our series (extrascleral involvement and involvement of optic nerve resection line). Multivariate analysis of the 149 patients without these classical risk factors revealed two factors that increase the risk of orbital and/or metastatic disease: massive choroidal invasion and postlaminar optic nerve involvement.
CONCLUSIONS: In our experience, retrolaminar optic nerve involvement, with free resection line, and massive choroidal invasion significantly increase the risk for orbital and/or metastatic disease.