Frequency and Clinical Course of Residual Orbital Masses After Treatment of Orbital Rhabdomyosarcoma.

purposeTo evaluate the frequency and clinical course of residual orbital masses on imaging studies after multimodality treatment for orbital rhabdomyosarcoma.

designRetrospective case series.

methodsWe reviewed records of patients with primary orbital rhabdomyosarcoma who underwent chemotherapy and radiotherapy after surgical biopsy or debulking at 4 US centers during 1998-2019. Demographics, histologic subtype, tumor response 12 weeks after chemotherapy initiation and after completion of all treatment, and imaging findings were analyzed.

resultsThirty-two patients met inclusion criteria. Twenty-two were male, and 30 were younger than 18 years. Histologic subtype was embryonal in 22 patients, alveolar in 8, and mixed embryonal/alveolar in 2. Median follow-up time was 46 months (range, 4.9-199 months). Two patients died. Twenty-seven patients had reliable end-of-treatment imaging findings, of whom 9 had a residual mass. Three residual masses disappeared spontaneously (by 4, 32, and 53 months), 2 remained at last contact, at 2 and 7 years of follow-up, and 3 were excised; 1 progressed and underwent an exenteration. Complete response at 12 weeks was associated with complete response at the end of treatment (P < .001). Patients with T1 or T2 tumor at presentation were more likely to have complete response at last contact than were those with T3 or T4 tumor (P < .05). Biopsy type (incisional or excisional) was not associated with response to treatment at any time point.

conclusionA residual orbital mass on imaging may be present after multimodality treatment in approximately one-third of patients. Resolution without biopsy or excision varied from months to years.