Radiation regression patterns in treated retinoblastoma: 7 to 21 years later.

A retrospective review of cases on file at the Ophthalmic Oncology Center of The New York Hospital-Cornell Medical Center, New York was performed in order to examine the appearance of radiation regression patterns 7 or more years after successful treatment of retinoblastoma with external beam radiotherapy. Forty-eight patients were found to have 89 tumors in 57 eyes which were treated solely with external beam radiation; they were followed for a minimum of 7 years and had sufficient information available for analysis. All but five of the patients had bilateral retinoblastoma. Seventy-four of the 89 tumors continued to be ophthalmoscopically visible after 7 or more years. Taking into account those that did change between the time of first evaluation (usually at the completion of treatment) and final evaluation (7 or more years after treatment), the number of Type I regressions increased by 10.1%, Type IIs decreased by 19.1%, Type IIIs fell by 7.8%, Type IVs rose by 10.1%, and the number of tumors that disappeared increased by 6.8%. Type II remained the most common regression throughout the follow-up. The regression with the greatest potential for change was the Type II regression. The pretreatment volume of the tumor correlated with long-term radiation regression patterns. The smallest tumors (mean size 1.1 dd [disc diameter] or less in size) completely disappeared, while the largest (mean 9.9 dd) became Type I regressions.