An Evaluation of Radiotherapy and Response in the Management of Perivascular Epithelioid Cell Tumors

OBJECTIVES: Perivascular epithelioid cell tumours (PEComas) are ultra-rare soft tissue tumours with heterogeneous treatment approaches. While surgery is the standard for localized disease, the role of radiotherapy (RT) remains unclear. METHODS: This retrospective study aims to evaluate tumour volume response, as well as local outcomes and Overall Survival, in patients with PEComa treated with RT. The cohort included patients diagnosed with PEComa between 2005 and 2023 at a single sarcoma centre. Demographic, clinical, RT, and volumetric tumour data were collected. Response was assessed using RECIST v1.1. RESULTS: In total, 24 lesions in 12 patients were evaluable for analysis, with a median radiological follow-up of 10 months. Of these, 7 lesions were treated with perioperative RT and 17 with palliative RT. Systemic treatments during imaging follow-up were administered in 19/24 lesions. Among 17 lesions treated with palliative intent without surgery, four local failures occurred- all at EQD2 (α/β = 5) <40 Gy- and the estimated 1-year local control rate was 61.9%.Among these 17 lesions, mean tumour volume decreased from 301.5 cm³ (range: 0.9-2251) to 108.3 cm³ (range: 0.1-754) as best response after RT. Seven patients (58.3%) died from their disease, with a median overall survival of 46 months after diagnosis. CONCLUSION: PEComas appear to be radiosensitive, with substantial tumour volume reduction after RT and a dose-response signal favouring higher EQD2 dose. Nonetheless, overall survival was poor, reflecting the aggressive nature of this disease. ADVANCES IN KNOWLEDGE: This is the largest RT series in PEComa to date and suggests radiosensitivity in this disease.