Iodine 125 plaque radiotherapy as salvage treatment for retinoblastoma recurrence after chemoreduction in 84 tumors.

Purpose: To assess tumor control and complications of iodine 125 (I125) plaque radiotherapy for retinoblastoma recurrence after chemoreduction (CRD).

Design: Interventional retrospective case series.

Participants: Children with retinoblastoma treated on the Oncology Service, Wills Eye Hospital, initially examined from July 1994 to April 2005.

Methods: Eighty-four retinoblastomas with solid recurrence after CRD were treated with custom designed I125 plaque radiotherapy. Eyes with vitreous or subretinal seed recurrence were excluded. The CRD regimen included vincristine, etoposide, and carboplatin for 6 cycles plus local consolidation with thermotherapy or cryotherapy. The only alternatives to plaque radiotherapy in these cases would have been external beam radiotherapy (EBRT), additional chemotherapy, or enucleation.

Main Outcome Measures: Tumor control and radiation complications.

Results: Tumor control was achieved in 95% of eyes by 5 years follow-up. Of the 59 recurrent tumors after CRD alone, 56 (95%) were controlled with plaque radiotherapy. Of the 25 recurrent tumors after CRD and EBRT, 100% were controlled with plaque radiotherapy. Of the 3 failures after plaque radiotherapy, the median time to failure (tumor recurrence) was 4 months and all recurrences were detected within 1 year. There were no identifiable factors predictive of plaque radiotherapy failure. Using Kaplan-Meier analysis, radiation complications at 5 years included proliferative retinopathy (19%), nonproliferative maculopathy (24%), papillopathy (16%), transient mild vitreous hemorrhage (54%), cataract (43%), iris neovascularization (NVI; 8%), and glaucoma (4%). Nonresolving vitreous hemorrhage and scleral necrosis did not occur. Radiation complications showed minimal change at 10 and 15 years of follow-up.

Conclusions: Iodine 125 plaque radiotherapy offers 95% tumor control for selected retinoblastomas that fail CRD. Complications such as radiation retinopathy and mild vitreous hemorrhage should be anticipated, depending on the location, size, and extent of the tumor.