Preliminary results of primary chemotherapy in retinoblastoma

Eye retention rates after external beam therapy for advanced retinoblastoma are close to 90% with very few ocular side effects like radiation retinopathy or radiation induced optic neuropathy. Late complications, however, comprise a sixfold increase of secondary non-ocular cancers like soft tissue sarcomas demanding alternative treatment options in the management of advanced retinoblastoma.

A phase I study on primary chemotherapy using vincristine, cyclophosphamide, etoposide and carboplatin in advanced bilateral retinoblastoma was undertaken to evaluate the potential of a treatment regimen not including external beam therapy.

12 eyes with 17 tumors in 9 children were treated with primary chemotherapy as first treatment option with a mean follow-up of 16.7 months. Planned enucleation of a tumor containing eye was performed in 2 eyes. In one of these enucleated eyes no viable tumor cells were visible on histopathological examination while in the other eye marked tumor regression was detectable. Of the remaining 10 eyes clinical regression of the intraocular tumors was present in all eyes; on average the tumor size was reduced by 50% within 3-6 weeks. Most of the tumors showed a type I (cottage cheese) regression indistinguishable from regression patterns found after external beam radiotherapy. Ancillary treatments including laser photocoagulation, beta-ray brachytherapy, external beam radiotherapy and cryotherapy were performed in 15 out of the 17 tumors.

Based on the results of this study and on the results published by others primary chemotherapy may result in the same eye retention rate as conventional external beam therapy avoiding the unacceptable high rate of secondary non-ocular cancers in the latter. A prospective study to be undertaken by the GPOH (Gesellschaft für Pädiatrische Onkologie und Hämatologie) and the RG (Retinologische Gesellschaft) is planned to further evaluate this new and promising approach.