Orbital Myeloma and Plasmacytoma: An Australian Study.

PURPOSE: The purpose of this study was to provide Australian data on the clinical and radiological features and outcomes in patients with orbital plasmacytomas.

METHODS: Multicentre retrospective review of orbital plasmacytoma and orbital involvement in multiple myeloma (MM) from 2005 to 2022 in Australia.

RESULTS: Twenty-one participants were identified. The median age was 62 years (range 34-88 years), and 11 (52%) were females. Eighteen (84%) had a known diagnosis of MM prior to their orbital presentation, with all patients eventually being diagnosed with systemic MM. Thirteen (72%) were receiving active treatment for systemic myeloma on presentation, while 3 (17%) were in remission. All but 1 had unilateral orbital involvement (n = 20, 95%). Common presenting symptoms and signs were decreased visual acuity (n = 13, 62%), proptosis (n = 11, 52%), limited motility (n = 15, 71%), and optic neuropathy (n = 5, 24%). Radiologically, 15 (71%) involved the superotemporal orbit, 7 (33%) inferotemporal orbit, and 16 (76%) involved ≥1 extraocular muscle. Sixteen (76%) were biopsied and confirmed orbital plasmacytoma on histopathology. Treatment modalities included intravenous and oral steroids (n = 7, 33%), chemotherapy (n = 9, 43%), radiotherapy (n = 13, 62%), stem cell transplant (n = 3, 14%), and surgical debulking and decompression (n = 3, 14%). Mortality was high, with 15 (71%) having MM-related mortality.

CONCLUSIONS: This is the largest cohort of Australian data on orbital plasmacytomas. Most patients have a diagnosis of systemic MM at presentation. It is crucial to recognize and treat these patients early due to a poor systemic prognosis.