Plaque radiotherapy for selected orbital malignancies: preliminary observations: the 2002 Montgomery Lecture, part 2

To describe the principles and preliminary results of plaque brachytherapy for selected orbital malignancies.

A custom-designed Iodine-125 plaque, designed to deliver a target dose of 50 Gray, was placed surgically in the region from which an orbital malignancy was partially resected. The mean dose to the target area was 50 Gray. The initial and follow-up patient data were reviewed.

Of the 8 patients, the diagnosis was adenoid cystic carcinoma of the lacrimal gland (4 cases), orbital invasion by basal cell carcinoma (2), orbital extension of conjunctival melanoma (1), and metastatic carcinoma (1). Of the 4 with adenoid cystic carcinoma, there was microscopic residual tumor after excision and orbital exenteration was considered. Three have tumor control with follow-up of 1, 3, and 6 years. One patient required exenteration for recurrence separate from the field of brachytherapy and is free of tumor after 10 years. All 4 patients are alive and well with tumor control. Of the 2 patients with orbital extension of basal cell carcinoma, tumor control without recurrence has been achieved in both after 2 years. The patient with orbital metastasis responded to plaque radiotherapy, with no orbital recurrence, but died of systemic metastasis. The patient with orbital melanoma had local orbital recurrence separate from the area of irradiation and is currently being treated for systemic metastasis.

Based on preliminary observations, plaque radiotherapy appears to be a reasonable alternative to exenteration and external irradiation for selected orbital malignancies.