ICRB Classification of Retinoblastoma
-The Reese-Ellsworth Classification system was developed in the 1950's to predict probability of eye preservation after external beam radiation for retinoblastoma (Rb)
-This system did not provide any prognostic information for patient survival or visual acuity
-Eventually, there was a shift in treatment paradigm from radiation to chemotherapy since the former is associated with risk of secondary tumors (e.g. osteosarcoma)
-New classification system (International Classification System for Intraocular
Retinoblastoma) was proposed in 2005 to give more useful prognostic information given this shift to other treatments besides external beam radiation
GROUP A (very low risk)
- Tumour ≤ 3 mm in basal dimension or thickness
- 3 mm from the fovea
- 1.5 mm from the optic disc
GROUP B (low risk)
- Tumour > 3 mm in basal dimension/thickness, or any of the following
- ≤ 3 mm to the fovea
- ≤ 1.5 mm to optic disc
- Clear subretinal fluid ≤3 mm from margin
GROUP C (moderate risk)
- subretinal seeds ≤3 mm from tumour
- vitreous seeds ≤3 mm from tumour
- both subretinal and vitreous seeds ≤3 mm from tumour
- less than one quadrant of subretinal fluid in the fundus
GROUP D (high risk)
- subretinal seeds >3 mm from tumour
- vitreous seeds > 3 mm from tumour
- Both subretinal and vitreous seeds >3 mm from tumour
- Greater than one quadrant of subretinal fluid in the fundus
GROUP E (very high risk)
Extensive Rb or one of the following:
- Neovascular glaucoma
- Diffuse infiltrating tumor
- Orbital celluitis or phthisis bulbi
- Opaque media from hemorrhage in anterior chamber, vitreous, or subretinal space
- Invasion of postlaminar optic nerve, choroid, scera, anterior chamber, orbit
- Tumour anterior to the anterior vitreous face, including the ciliary body or iris
Image from Rajan Eye Care Hospital
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