Effectiveness of brachytherapy in the combination treatment of retinoblastoma

Background: Retinoblastoma is a malignant tumor of the eye retina that occurs mostly in children. In the absence of treatment, the disease leads not only to vision loss, but also to death of the child. At present, combined organ-preserving methods of treatment are preferred. These include polychemotherapy and a local intervention on the tumor, the "golden standard" of which being brachytherapy.

Aim: To study the effectiveness of brachytherapy against the background polychemotherapy.

Materials and methods: We analyzed retrospectively medical files of 104 children with retinoblastoma aged from 5 months to 5 years (mean age 21  months), who underwent brachytherapy as a local component of management from 2010 to 2015 in the Moscow Helmholtz Research Institute of Eye Diseases. Multifocal lesions were identified in 43 cases and bilateral tumors in 87 children. In 33 cases, the worst eye was removed. Endophytic and mixed forms of tumors growth were most prevalent. Before the brachytherapy, all children received polychemotherapy (2 to 3 courses). The average tumor thickness was 2.74 mm (from 1 to 6.4 mm); its mean maximal transverse dimension was 6.27 mm. Indigenous ophthalmic applicators with isotopes ⁹⁰Sr + ⁹⁰Y and ¹⁰⁶Ru + ¹⁰⁶Rh were used. The average dose on the tumor apex with the strontium applicator was 142.1 (120–170) Gy, with ruthenic one, 107.4 (69–168) Gy; the scleral doses were 751.3 и 504.4 Gy, respectively. The median follow-up was 51 months. The patients were assessed every 3 to 4 months with ophthalmoscopy and ultrasound examination. The following effectiveness criteria were used: complete resorption, the tumor cannot be identified; partial resorption, a decrease in the initial tumor size by at least 50%; no effect, a decrease in the initial tumor size by less than 50% or an increase in the size of the tumor.

Results: Complete resorption of the tumor occurred in 60.6% (n = 63) of the patients at 3 months and in additional 24% (n = 25) at 6 months. During the first year after the radiation, complete resorption of retinoblastoma was achieved 93.3% (n = 97) of the children. All children are alive, no distant metastases have been found. Early complications after brachytherapy were noted in 3  children: hemophthalmia, in 1, retinal detachment, in 1, hemophthalmia with retinal detachment, in  1, when the radiation dose on the sclera exceeded 1000  Gy. Continued tumor growth or relapses were detected in 7 (6.7%) patients. The reason to enucleate two eyes was the tumor invasion into the orbit (1.9%). Visual functions are preserved in 85 (81.7%) children, with a high visual acuity (0.9–1.0) in 21 children, and 0.1–0.8 in 21 children, as well.

Conclusion: Brachytherapy is a highly effective method of local destruction of retinoblastoma, which, in the vast majority of cases, allows for complete resorption of the irradiated tumor and for maintenance of high visual acuity in almost half of patients.