Background: Chemoreduction is a method of reducing tumor volume to allow for more focused, less damaging therapeutic measures.
Objective: 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.
Methods: 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.
Results: 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.
Conclusion: 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.