Unilateral vs. bilateral retinoblastoma. Correlations between age at diagnosis and stage of ocular disease.

Retrospective analysis of 358 cases of retinoblastoma for correlation between age and intraocular stage at the time of diagnosis revealed: in both early and advanced stages of intraocular disease, bilateral retinoblastoma presents at an earlier age than does unilateral retinoblastoma; support for the Knudson "two-hit" hypothesis of retinoblastoma genetics, the existence of a positive family history for retinoblastoma does not guarantee an earlier age at diagnosis compared to sporadic disease; and for any age at diagnosis, unilateral or bilateral disease, Group V is the most common intraocular stage found.