Choroidal Invasion of Retinoblastoma: Metastatic Potential and Clinical Risk Factors

There is considerable debate about the significance of choroidal invasion of retinoblastoma with regard to metastatic disease. The charts of patients with retinoblastoma were reviewed over a 17 year period to determine the frequency of histopathological choroidal invasion of retinoblastoma and its risk for eventual metastatic disease. Sixty seven of 289 eyes (23%) enucleated for retinoblastoma had histopathological evidence of choroidal invasion. Those patients with choroidal invasion (with or without optic nerve invasion) were more likely to develop metastases than those without choroidal invasion (p = 0.0001). When considering those patients with isolated choroidal invasion of retinoblastoma, excluding those with associated optic nerve invasion, there was no significant risk but there was a trend towards the development of metastases (p = 0.10). The clinical factors found to be predictive for choroidal invasion from retinoblastoma from a univariate analysis included increased intraocular pressure (p = 0.04) and iris neovascularisation (p = 0.007) and, from a multivariate analysis, iris neovascularisation (p = 0.02). The histopathological factors statistically associated with choroidal invasion included the presence of optic nerve invasion (p = 0.002) and poorly differentiated retinoblastoma (p = 0.003). Factors not predictive for choroidal invasion included the age, race, and sex of the patient and the tumour laterality, inheritance, size, and growth pattern. Choroidal invasion of retinoblastoma is a risk for metastases, especially if it is associated with any degree of optic nerve invasion.