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Ocular preservation after 36 Gy external beam radiation therapy for retinoblastoma
Thomas E Merchant1, Ciara J Gould, Nathan E Hilton
1Department of Radiation Oncology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA. thomas.merchant@stjude.org
Purpose:
The purpose of this study was to document the ocular preservation rate after 36 Gy external beam radiation therapy (EBRT) for retinoblastoma.
Patients And Methods:
Forty-nine eyes of 38 patients were treated with a median dose of 36 Gy EBRT. The patient population included 7 unilateral and 31 bilateral presentations, with a median age at diagnosis of 4 months. Eyes enucleated at the time of diagnosis or treated with other measures were not included in the analysis of ocular preservation. The median age at EBRT was 8 months. Patients were monitored for progression of disease after EBRT and second malignant neoplasms.
Results:
The median follow-up was 88.6 months, with an estimated ocular preservation rate of 82.0% +/- 5% at 10 years. There was a difference in the ocular preservation rates for patients with advanced disease (Reese-Ellsworth group III-V) compared with early disease. Metastatic disease developed in two patients, and a second malignant neoplasm developed in three. Patients treated with en face electrons experienced a lower 5-year estimate of ocular preservation than those treated with photons, although patients treated with electrons were more likely to have advanced disease.
Conclusions:
The use of low-dose EBRT (36 Gy) results in ocular preservation rates that are comparable to those of high-dose EBRT. The use of electrons requires careful treatment planning and computerized dosimetry.