Transpupillary thermotherapy as initial treatment for small intraocular retinoblastoma: technique and predictors of success.

OBJECTIVE: To determine which small retinoblastoma tumors can be treated with transpupillary thermotherapy (TTT) alone and to clarify the minimum amount of treatment required to prevent recurrence.
DESIGN: Noncomparative interventional case series. PARTICIPANTS: Ninety-one tumors in 22 eyes of 24 patients were treated with TTT as the primary treatment modality at a single institution from 1995 until 2002.
METHODS: Transpupillary thermotherapy was applied only when a tumor first appeared or if growth subsequently occurred. Treatment was performed while patients were under general anesthesia with the Iris diode laser (810 nm) on continuous mode with a 1.2-mm spot size. MAIN OUTCOME MEASURES: Local tumor recurrence, failure of TTT requiring the use of salvage therapies.
RESULTS: Mean age at diagnosis was 3 months (range, 0-19 months), and mean initial tumor base was 0.67 disc diameters (DD) (range, 0.1-1.5). Eighty-four tumors (92%) were cured with TTT alone. Seven tumors (8%) required between 1 and 5 salvage treatments: 4 tumors received cryotherapy, 3 tumors received systemic chemotherapy, 2 tumors received external beam radiation, and 1 tumor received periocular chemotherapy. All 7 tumors requiring salvage treatment were cured without enucleation. Twenty-one eyes were preserved (95%), with 1 eye enucleated secondary to growth of other tumors. The mean number of treatment sessions required for cure was 1.7 (median, 1 session, range 1-6), with 64% of the tumors requiring only 1 session. The mean power was 420 mW, the mean total duration for all sessions was 320 seconds, and the mean total energy for all treatments was 139.6 J. Univariate analysis revealed that predictors of tumor recurrence were male gender, increasing age at diagnosis, posterior and inferior tumor location, increasing initial tumor base diameter, and increasing total energy. Multivariate analysis indicated that the predictive combination of variables included male gender, increasing age at diagnosis, and increasing total energy. The predictors of need for salvage treatment on univariate analysis were male gender, inferior tumor location, increasing initial tumor base diameter, and increasing total energy. Multivariate analysis demonstrated that the most important combination of variables was male gender and increasing total energy.
CONCLUSIONS: Retinoblastoma tumors <1.5 DD in base diameter can be successfully treated with TTT alone. Treatment can be implemented only when recurrences occur and can be used at low power settings for a short duration.