External beam radiation for localized periocular amyloidosis: a case series.

: To evaluate the effectiveness of low dose external beam radiation therapy to halt progression of localized periocular light chain (AL) amyloidosis, a clonal plasma cell disorder. : This is a retrospective review of patients referred to a tertiary care center for external beam radiation treatment of biopsy proven localized periocular light chain amyloidosis. The primary outcome measure was clinical disease stability at one year following radiation therapy as evidenced by slit lamp exam and external photography. Pre and post radiation MRI imaging of the affected area were also used as a means to monitor disease progression. : Four symptomatic patients with localized periocular AL amyloidosis received external beam radiation therapy ranging from 20-30 Gy fractioned over 10-20 fractions. Three of the four patients had prior surgical debulking with or without ptosis repair. Amyloid deposition did not progress in any patient at one year. Further follow-up of two patients revealed amyloid progression at two years post radiation. : External beam radiation therapy for localized periocular AL amyloidosis demonstrated efficacy at halting disease progression at one year; however, the long-term efficacy is unknown. Monitoring of periocular amyloid is best achieved with slit lamp exam and external photography as opposed to MRI.