Bilateral retinoblastoma. Correlations between age at diagnosis and time course for new intraocular tumors.

A retrospective analysis of 355 eyes from 325 patients with bilateral retinoblastoma followed for at least five years was analyzed for the development of new ocular tumors. Eighty-eight eyes (24.8%) developed new tumors with more than 95% of these seen in patients diagnosed before the age of two years. Excluding one patient, no new tumors were seen in patients who were initially diagnosed after 33 months of age. The relative risk for developing new tumors was greater (45.1%) for patients diagnosed within the first six months of life than for patients diagnosed after the age of six months (14.2%). The highest percentage of patients (58%) to develop new tumors were those diagnosed before the age of three months. In patients initially treated before two years of age, new tumors were noted to develop up to 4.5 years later, whereas among eyes diagnosed after the age of two years, 100% of all new tumors were seen before 1.5 years of follow-up. Regardless of the age at diagnosis, however, the upper age limit for new tumor development ranged from 4.0-6.25 years, with a mean of 5.1 years. All new tumors were managed with either photocoagulation/cryotherapy or plaques.