Focal therapy in the management of retinoblastoma: when to start and when to stop.

PURPOSE: To describe the treatment effects and side effects of different modalities of focal treatment used for retinoblastoma.

METHODS: Green (532-nm) laser, continuous wave Nd:YAG (1064-nm) laser, transpupillary or transcleral (810-nm) laser, and cryotherapy were used in the treatment of 46 eyes in 35 patients affected with retinoblastoma. The number of treatment sessions and the amount of energy applied were recorded in an attempt to determine the amount of energy required to adequately treat tumors of various sizes. In addition, we have attempted to determine when treatment becomes overtreatment and is likely to lead to complications.

RESULTS: The treatment endpoint for laser in this study was calcific, gliotic, or flat scars. Small tumors (<2 mm in height, <4 DD) were successfully treated in 3 or fewer sessions of 532-nm laser. Anterior small tumors were successfully treated with transcleral 810-nm laser or cryotherapy. Medium tumors, between 2.0 and 4.0 mm in thickness, required 2 to 9 treatments to achieve a good response and often required the addition of chemotherapy to reduce the size of the tumor before or during laser treatment. Large tumors required chemotherapy combined with many laser treatments for complete control. Complications associated with excessive laser were vitreous condensation with traction, vitreous hemorrhage, retinal detachment, tumor break, cataract formation, and iris burns.

CONCLUSION: Laser treatment alone for small tumors, and combined with cryotherapy and chemotherapy for larger tumors, is effective in the treatment of retinoblastoma. Complications of focal therapy can most often be avoided by using the minimal effective laser power.