Conditional analysis on new tumor formation with solitary unilateral retinoblastoma in 482 consecutive patients

The objective of the study was to understand dynamic risk (conditional analysis based on patient age) for new tumor development in patients with solitary unilateral retinoblastoma.

This was a retrospective analysis.

Of 482 patients with solitary unilateral retinoblastoma, 55 new tumors developed in 20 patients (4%). Comparison (new tumor vs. no new tumor development) revealed those with new tumor demonstrated younger mean age at presentation (10 vs. 36 months, P < 0.001), greater likelihood of family history of retinoblastoma (35% vs. 3%, P < 0.001), and greater probability of primary tumor location in the macula (50% vs. 15%, P = 0.003). Conditional risk for new tumors (at age 6, 9, 12, 18, and 24 months) declined for those who presented at 0-3 months old (25%, 15%, 15%, 8%, and 0%), >3-6 months old (17%, 14%, 6%, 6%, and 0%), >6-9 months old (not applicable [na], 6%, 6%, 0%, and 0%), and >9-12 months (na, na, 3%, 3%, and 0%). Younger patients showed greater development of bilateral tumors (P < 0.001). Of patients with new tumors, those that occurred within 1 year from presentation were located in the preequatorial region in 46%, whereas those that occurred more than 1 year from presentation were preequatorial in 78%. Patients ≤24 months at initial presentation demonstrated all new tumors by 24 months of age. Older patients (>24 months at presentation) showed new tumors up to 56 months of age.

Children (≤24 months) with solitary unilateral retinoblastoma showed decreasing risk for new tumors up to 24 months of life. Later onset of new tumor was more likely located in preequatorial region.