Chemoreduction in the initial management of intraocular retinoblastoma

Chemoreduction is a method of reducing tumor volume to allow for more focused, less damaging therapeutic measures.

To determine whether chemoreduction could be used to decrease the size of retinoblastoma so that enucleation or external beam radiotherapy could be avoided and more conservative modalities employed.

A prospective pilot study was performed to assess the effectiveness of a 2-month chemoreduction regimen of vincristine sulfate, etoposide, and carboplatin in patients with retinoblastoma. The study included 20 patients with 54 tumors in 31 eyes.

At the initial examination, the mean tumor base was 12 mm and the thickness, 7 mm. Vitreous seeds were present in 14 eyes (45%). A secondary retinal detachment was present in 24 eyes (77%) and, when present, involved a mean of 71% of the retina. In 11 eyes (36%) the retina was totally detached with serous subretinal fluid. After 2 months of chemoreduction, all 54 tumors showed regression in size, and 48 (89%) showed evidence of calcification. The mean tumor base was 8 mm and the thickness, 4 mm. Overall, there was a mean 35% decrease in base and 49% decrease in thickness of the tumor at the end of the treatment period. A complete response was found in 25 tumors (46%) and a partial response in 29 (54%). The subretinal fluid had resolved completely in 50% of the cases (12/24 eyes), and, in the 11 eyes with total retinal detachment, the subretinal fluid had completely resolved, leaving flat retina, in 6 eyes (54%). The vitreous seeds demonstrated some degree of regression in all cases, and in 5 eyes there was 90% to 100% calcification of the seeds. Short-term systemic toxic effects were mild (transient bone marrow suppression). Enucleation was avoided in all cases; external beam radiotherapy was necessary in 9 eyes because of diffuse vitreous seeds. The remaining 22 eyes were treated with local methods after chemoreduction.

Tumor shrinkage with chemoreduction may allow treatment with less invasive measures, such as cryotherapy, laser photocoagulation, thermotherapy, or plaque radiotherapy, thereby avoiding enucleation and external beam radiotherapy.