New tumours in non-enucleated eyes of bilateral retinoblastoma patients

Forty non-enucleated eyes with bilateral retinoblastoma which were treated by external beam radiation therapy (EBRT), transconjunctival cryopexy, and photocoagulation were retrospectively analysed for the age of onset and location of new intraocular tumours. Of these 40 eyes, 9 (22.5%) eyes developed 17 new tumour foci over a mean follow-up of 3 years. The risk of new tumour formation was age-related being 47% in children with age at onset of retinoblastoma less than 1 year compared to 4.4% in older children (P < 0.001). Four eyes (44%) had 2 episodes of tumour formation. All tumour foci developed within 11 months of initial treatment at an average episode interval of 4.0 months. In 89% of cases, new lesions ceased to occur by 18 months of age. Our study clearly shows that EBRT did not prevent development of new lesions. The tumour islands which developed in the peripheral retina in 88% of cases were successfully treated with transconjunctival cryopexy. In 8 cases (89%), the eye could be salvaged. All young bilateral retinoblastoma patients should undergo frequent periodic detailed examination of the retinal periphery with 360 degrees scleral depression to pick up new tumour lesion early and to treat them effectively with simple globe saving methods.