PURPOSE: To compare the difference in volume between enucleated and contralateral, uninvolved orbits in patients with unilateral retinoblastoma treated with primary enucleation who received either hydroxyapatite or solid silicone implants. METHODS: In this retrospective, comparative interventional case series, data were reviewed for all patients (N = 33) with retinoblastoma at St. Jude Children's Research Hospital who underwent unilateral enucleation and received either hydroxyapatite or solid silicone implant from 1969 to 1999. Patients who received external beam radiation or systemic chemotherapy were excluded. CT and/or MRI were used to compare the difference in orbital volumes between the enucleated orbit and the contralateral orbit in 13 patients who underwent enucleation with hydroxyapatite implants vs. 20 patients who underwent enucleation with silicone implants. The main outcome measure was the difference in volume between enucleated and contralateral, uninvolved orbits correlated to implant material, which we determined using the Wilcoxon rank sum test. RESULTS: The median difference in orbital volumes between enucleated and contralateral, uninvolved orbits was 0.9 cm (range, -3.78 to 3.09 cm; quartiles, -0.37, 2.72 cm; mean ± standard error [SE], 0.76 ± 0.64 cm; 95% confidence interval [CI], -0.49 to 2.01 cm) for patients treated with hydroxyapatite implants vs. 0.63 cm (range, -4.43 to 3.91 cm; quartiles, 0, 2.13 cm; mean ± SE, 0.8 ± 0.41 cm; 95% CI, -0.004 to 1.6 cm) in patients treated with silicone sphere implants. The median differences did not differ between the 2 types of implant (p = .74). The median follow-up time was 137 months (range, 10-244 months; quartiles, 37, 179 months; mean ± SE = 118.31 ± 22.83 months; 95% CI, 73.56-163.06 months) and 144 months (range, 57-251 months; quartiles, 98, 154 months; mean ± SE, 136.1 ± 10.78 months; 95% CI, 114.97-157.23 months), respectively. CONCLUSIONS: In unilateral retinoblastoma patients treated with primary enucleation, hydroxyapatite-integrated orbital implants provide no better symmetry of orbital volume than do more traditional silicone implants.
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