This retrospective study found that multisession Gamma knife radiosurgery is an effective treatment for solitary, benign, well-circumscribed orbital apex tumors.
The authors reviewed their treatment with multi-session Gamma knife irradiation of five patients with presumably benign orbital apex tumors, including three cases of cavernous hemangioma and two schwannoma. Each tumor was located stereotacticly, and patients underwent four sessions on four consecutive days with a radiation dose of 10 Gy to the tumor and 5 Gy to its margins with a prescription isodose of 50% (and not the usual 80%).
After a follow up of eight to 68 months, all patients demonstrated improvement in visual acuity, pupillary responses, color vision and visual field, and three patients achieved 20/20 vision. Of the two patients who did not achieve maximal visual function: one had long-standing compressive optic neuropathy and the other had pre-existing epiretinal membrane. Complete resolution of the visual field defect was seen in four patients.
Tumor shrinkage was observed in all patients and remained stable until the last follow-up visit. No adverse events were noted during or after radiosurgery, and none of the patients experienced any radiation-related ocular morbidity.
The authors say the major advantage of this treatment is the need for fewer treatment sessions and a shortened treatment period, as well as the high accuracy permitting high-dose irradiation with a lower possibility of complications. This avoids the complications associated with surgical resection and conventional radiotherapy.
Nevertheless, the number of patients and the follow-up period were limited in the current study. Benign orbital tumors expand very slowly over years, and it is unknown if they will regrow and if they do, if the treatment could be repeated or another intervention will be required.