EP617 Second line treatment in metastatic uterine pecoma

Introduction/Background Uterine perivascular epithelioid cell tumors (PEComas) are rare neoplasms associated with upregulation of the mTOR pathway, frequently through inactivation of TSC1/TSC2. The treatment of advanced and metastatic PEComas is challenging, especially after progression on mTOR inhibitors. Some reports suggest anti-angiogenic agents as a potent second line treatment. We report the effect of pazopanib for a patient with metastatic uterine PEComa progressing on everolimus. Methodology A 53-year-old patient was admitted for a four-month history of vaginal bleeding. Clinical examination and vaginal ultrasound indicated a 6 × 6 cm uterine mass and PET-CT identified a bone lesion S1. The patient was treated with radical hysterectomy. Both bone biopsy and hysterectomy indicated an oligo-metastatic PEComa with high-grade nuclear features and lymphovascular invasions. The single bone metastasis was treated with radiotherapy, but three months later the patient presented bone, lung and subcutaneous recurrence. Targeted NGS (52-cancer gene hotspot panel) detected no mutation but an heterozygous deletion of 9q34, that contains the TSC1 gene, prompting a first line everolimus treatment. For the bone metastasis denosumab was initiated. On this treatment, the disease was controlled for two years before symptomatic subcutaneous progression. A second line treatment by pazopanib and denosumab was introduced, based on reports on anti-angiogenic tyrosine kinase inhibitors (TKIs) effect in PEComas. Results With the combination of pazopanib and denosumab, there was regression of the subcutaneous disease and stability of lung and bone metastasis for over a year. The treatment toxicities were mild and no dose adaptation was necessary. Conclusion Our report provides evidence that anti-angiogenic targeted therapy with pazopanib, a multi TKI, is an effective second line treatment for metastatic malignant PEComas progressing after mTOR inhibition. The toxicity profile of the association was acceptable in line with the previously reported toxicities of the respective drugs. Disclosure Nothing to disclose.