A retinoblastoma will undergo regression following radiation therapy. This tends to follow one of several patterns. With radiation therapy the tumor need not disappear to be cured.
Types of radiation used:
(1) external beam
(2) brachytherapy with cobalt plaques
NOTE: Radiation therapy is used cautiously today because of the risk of secondary extraocular tumors in patients with hereditary retinoblastoma.
Parameters:
(1) degree of regression (tumor shrinkage)
(2) appearance
(3) calcifications
Tumor Size
Calcifications
Appearance
Type
rapid moderate to marked shrinkage
flocculent deposits
decrease in vascularity
I
none to minimal shrinkage
none
translucent with modest decrease in vascularity
II
minimal to moderate shrinkage
flocculent deposits
modest decrease in vascularity
III
completely disappears
none
flat, white scleral patch without vascularity
IV
Type IV regression is seen with cobalt plaque therapy but not with external beam radiation.
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