Phase II Trial of nab-Sirolimus in Patients With Advanced Malignant Perivascular Epithelioid Cell Tumors (AMPECT): Long-Term Efficacy and Safety Update.

Clinical trials frequently include multiple end points that mature at different times. The initial report, typically based on the primary end point, may be published when key planned co-primary or secondary analyses are not yet available. Clinical Trial Updates provide an opportunity to disseminate additional results from studies, published in JCO or elsewhere, for which the primary end point has already been reported.nab-Sirolimus is approved in the United States for the treatment of metastatic or locally advanced malignant perivascular epithelioid cell tumor (PEComa) on the basis of the primary analysis results of the phase II Advanced Malignant Perivascular Epithelioid Cell Tumors (AMPECT) trial (ClinicalTrials.gov identifier: NCT02494570). Results from the primary analysis were previously published; however, the median duration of response (mDOR) had not been reached at that time. Here, 3 years after the primary analysis, we report final efficacy and safety data (data cutoff: April 29, 2022). At study completion, the confirmed overall response rate (by independent radiologist review using RECIST v1.1) was 38.7% (95% CI, 21.8 to 57.8), with an additional converted confirmed complete response (n = 2). Median progression-free survival remained the same at 10.6 months (95% CI, 5.5 to 41.2). The mDOR was reached at 39.7 months (95% CI, 6.5 to not reached [NR]), and the median overall survival at completion was 53.1 months (95% CI, 22.2 to NR). The most common treatment-related adverse events (TRAEs) were stomatitis (82.4%) and fatigue and rash (each 61.8%). No new or unexpected adverse events occurred, and no grade ≥4 TRAEs were reported. These results highlight the long-term clinical benefit of nab-sirolimus in patients with advanced malignant PEComa, with a DOR of >3 years.

Systemic Treatments and Molecular Biomarkers for Perivascular Epithelioid Cell Tumors: A Single-institution Retrospective Analysis.

Perivascular epithelioid cell tumors (PEComa) are a large family of mesenchymal neoplasms, with variable clinical course. Evidence regarding treatment of advanced PEComas is scarce, with only one FDA-approved treatment available. The goals of this study were to provide data regarding systemic treatments for advanced PEComas and to identify biomarkers of prognostic relevance. This is a single-institution retrospective study of patients with advanced PEComas requiring systemic treatment, including malignant PEComa, angiomyolipoma (including the epithelioid variant), and lymphangioleiomyomatosis. Outcomes measured were overall survival (OS), first-line and combined progression-free survival (PFS), and tumor response. Kaplan-Meier, univariable, and multivariable Cox proportional hazards analysis were performed. A total of 29 patients were included, most with malignant PEComa (n = 17). Median OS was 204.9 months, while median PFS was 92.4 months from first-line, and 15.8 months for all lines combined. TFE3 overexpression correlated with higher risk of death (HR: 11.8, P = 0.04), and shorter median OS (P = 0.001). Chemotherapy and mTOR inhibitors showed similar OS (P = 0.84), and first-line PFS (P = 0.67). Combined PFS was similar between individual mTOR inhibitors, chemotherapy, immune checkpoint inhibitors and other treatments (P = 0.19). Different mTOR inhibitors demonstrated similar efficacy, making cost and availability important considerations when choosing a specific agent. mTOR inhibitors showed similar outcomes as chemotherapy, suggesting that these should be preferred whenever possible for patients with PEComas given the morbidity associated with chemotherapy. TFE3 overexpression highlighted a subgroup of PEComas with worse prognosis and more aggressive behavior. Significance: This study examines systemic treatments for advanced PEComas, a rare group of sarcomas, and identifies molecular biomarkers of prognosis. Our results show that mTOR inhibitors have similar efficacy as chemotherapy, and that TFE3 overexpression, on IHC or FISH, correlates with a more aggressive disease course.

A rare metastatic mesenteric malignant PEComa with TSC2 mutation treated with palliative surgical resection and nab-sirolimus: a case report.

BACKGROUND: Malignant perivascular epithelioid cell tumors (PEComas) are exceedingly rare malignant mesenchymal neoplasms with characteristic morphological and immunohistochemical (IHC) patterns. However, some malignant PEComas are poorly differentiated with atypical histopathological features, making a definitive diagnosis difficult. PEComas are most commonly found in females and often show either TSC1 or TSC2 alterations, which result in the activation of the mTOR pathway, or TFE3 fusions. Given these molecular characteristics, mTOR inhibitors have recently been approved by the FDA in the treatment of malignant PEComas, particularly in those with TSC1/2 alterations. Therefore, molecular analyses may be helpful for both the diagnostic workup of and predicting response to mTOR inhibitors in cases of malignant PEComas. CASE PRESENTATION: Here, we report a case of an aggressive, 23 cm mesenteric malignant PEComa with multiple peritoneal metastases in a young male patient. Pathological examination of the initial biopsy showed a malignant epithelioid neoplasm with high-grade morphology and atypical immunoprofile, which precluded a definitive diagnosis. Because of the patient's excessive transfusion requirements due to intra-tumoral hemorrhage, a palliative R2 resection was performed. Histopathological examination of the tumor revealed focal immunoreactivity for Melan-A, HMB-45, desmin, and CD117. Although a diagnosis of malignant PEComa was favored, other entities such as epithelioid gastrointestinal stromal tumor (GIST) or melanoma could not be definitively ruled out. Given the favored diagnosis, the patient was started on sirolimus, an mTOR inhibitor, rather than chemotherapy. Molecular analyses were performed and the tumor was found to harbor mutations in TP53 and TSC2, supporting a definitive diagnosis of malignant PEComa. The patient was then switched to nab-sirolimus, with initial stabilization of the disease. CONCLUSIONS: This report details a multidisciplinary approach for the diagnosis and management of a highly aggressive, metastatic malignant PEComa in a young male patient. The basis for the treatment of malignant PEComas with the recently FDA-approved mTOR inhibitor, nab-sirolimus, is also reviewed. In summary, this case highlights the importance of molecular analysis, particularly TSC1/2 alterations, for both the definitive diagnosis of malignant PEComas and predicting their response to nab-sirolimus.

TFE3-associated perivascular epithelioid cell tumor with complete response to mTOR inhibitor therapy: report of first case and literature review.

BACKGROUND: Perivascular epitheloid cell tumor (PEComas) are characterized by expression of both muscles, most often smooth muscle actin (in ~80% of cases) and melanocytic markers (mainly HMB-45 and Melan A). TFE 3-associated PEComas are new variant which are poorly defined due to their limited reports in literature. These tumors lack response to targeted mTOR inhibitor therapy due to lack of mutation in TSC gene. Hereby, we are reporting a case of TFE3 associated pelvic PEComa showing excellent response to Everolimus. CASE PRESENTATION: A 45-year-old female presented with complaint of abdominal mass and bleeding per vaginum for 4 months. She had a history of total abdominal hysterectomy 3 years back in view of abnormal uterine bleeding and exploratory laprotomy 7 months back to remove some pelvic mass. Imaging suggested of ill-defined heterogenous mass of 9.3 x 9.2 x 16 cm involving the uterus, cervix, and upper 1/3 vagina. Multiple omental and peritoneal deposits were also seen, making probable diagnosis of carcinoma endometrium. USG guided biopsy showed cores of fibrous tissue with the presence of cells in sheets with granular eosinophillic cytoplasm; IHC showed positivity for TFE-3, H Caldesmon, GATA-3, and Melan A- and HMB-45; and Ki 67 index was 35%. The basis of above diagnosis of PEComa was made and she was started on Everolimus; repeat imaging after 3 months of therapy showed complete response. CONCLUSION: We are reporting first case of malignant pelvic TFE 3 PEComa showing response to mTOR therapy. Identification of TFE 3 PEComa is important because they showed different biologic behavior then their conventional PEComa.

RETROPERITONEAL PERIVASCULAR EPITHELIOID CELL NEOPLASM (PECOMA) RESPONSE TO MTOR KINASE INHIBITION. A CASE REPORT WITH LITERATURE REVIEW.

Perivascular epithelioid cell tumors (PEComas) are a very rare group of neoplasms and were first reported in 1996. These tumors represent a family of mesenchymal neoplasms, related through activation of the mammalian target of rapamycin (mTOR) inhibitor signaling pathway. The objective of this case report is to demonstrate significant regression of the tumor after neoadjuvant treatment with an oral mTOR inhibitor, following surgical removal of the mass to avoid a multiorgan resection. We present a case of a 27-year-old female with retroperitoneal PEComa and evaluated the tumor with MRI and integrated 18F-FDG-PET/CT scans at presentation and serially during treatment with everolimus. After 6 months of treatment with everolimus the tumor showed a substantial size reduction. Therefore, a multiorgan resection could be omitted. The patient has not demonstrated any disease recurrence after nearly 2 years of follow-up. PEComas are tumors with unpredictable behavior. Our report indicates that treatment of PEComas with everolimus may achieve a significant clinical response. As indicated by our case and past reports, mTOR inhibitors may be one of the best treatment options for this disease.

nab-Sirolimus for Patients With Malignant Perivascular Epithelioid Cell Tumors.

PURPOSE: Malignant perivascular epithelioid cell tumor (PEComa) is a rare aggressive sarcoma, with no approved treatment. To our knowledge, this phase II, single-arm, registration trial is the first prospective clinical trial in this disease, investigating the safety and efficacy of the mammalian target of rapamycin inhibitor nab-sirolimus (AMPECT, NCT02494570). PATIENTS AND METHODS: Patients with malignant PEComa were treated with nab-sirolimus 100 mg/m2 intravenously once weekly for 2 weeks in 3-week cycles. The primary end point was objective response rate evaluated by independent radiology review. Key secondary end points included duration of response, progression-free survival, and safety. A key exploratory end point was tumor biomarker analysis. RESULTS: Thirty-four patients were treated (safety evaluable), and 31 were evaluable for efficacy. The overall response rate was 39% (12 of 31; 95% CI, 22 to 58) with one complete and 11 partial responses, 52% (16 of 31) of patients had stable disease, and 10% (3 of 31) had progressive disease. Responses were of rapid onset (67% by week 6) and durable. Median duration of response was not reached after a median follow-up for response of 2.5 years, with 7 of 12 responders with treatment ongoing (range, 5.6-47.2+ months). Twenty-five of 31 patients had tumor mutation profiling: 8 of 9 (89%) patients with a TSC2 mutation achieved a confirmed response versus 2 of 16 (13%) without TSC2 mutation (P < .001). The median progression-free survival was 10.6 months (95% CI, 5.5 months to not reached), and the median overall survival was 40.8 months (95% CI, 22.2 months to not reached). Most treatment-related adverse events were grade 1 or 2 and were manageable for long-term treatment. No grade ≥ 4 treatment-related events occurred. CONCLUSION: nab-Sirolimus is active in patients with malignant PEComa. The response rate, durability of response, disease control rate, and safety profile support that nab-sirolimus represents an important new treatment option for this disease.

Unusual paediatric sigmoid perivascular epithelioid cell tumour with regional lymph node metastasis treated using gemcitabine and docetaxel: a case report and literature review.

Perivascular epithelioid cell tumour (PEComa) is an extremely rare neoplasm with distinctive morphology and specific expression of immunohistochemical markers. The lesion is typically diagnosed in middle-aged women, with few reports of paediatric cases, and there is no standardized treatment for the tumour type. Here, the case of a 17-year-old female, who presented with painless haematochezia for 2 days and was diagnosed with gastrointestinal PEComa of the sigmoid colon with regional lymph node metastasis after serial examination, is presented. She was treated by surgical resection of the tumour and cytotoxic chemotherapy comprising 900 mg/m2 gemcitabine and 100 mg/m2 docetaxel every 3 weeks for six cycles. Haematochezia did not recur, and complete response was achieved, with progression-free survival at the 24-month follow-up examination. Surgical resection with adjuvant conventional cytotoxic chemotherapy may be considered as an option for treating gastrointestinal PEComa.

Sustained response to pembrolizumab in recurrent perivascular epithelioid cell tumor with elevated expression of programmed death ligand: a case report.

BACKGROUND: Perivascular epithelioid cell tumors are defined by the World Health Organization as "a collection of rare mesenchymal tumors composed of histologically and immunohistochemically distinctive perivascular epithelioid cells." Whereas localized perivascular epithelioid cell tumor is typically benign and treated successfully with surgical resection, prognosis for patients with advanced or metastatic perivascular epithelioid cell tumor is unfavorable, and there is no standard curative treatment. CASE PRESENTATION: We report a Caucasian case of metastatic perivascular epithelioid cell tumor previously treated with chemotherapy and surgery with elevated surface expression of programmed cell death ligand 1. Based on this result, treatment via immune checkpoint inhibition with the monoclonal antibody pembrolizumab was pursued. After 21 cycles, the patient sustained a complete response. Therapy was stopped after the 40th cycle, and she was moved to surveillance. She remained disease free 19 months off treatment. CONCLUSIONS: This case report of a patient with perivascular epithelioid cell tumor treated successfully with programmed cell death protein-1 targeted therapy suggests that programmed cell death ligand-1 levels should be measured in patients with perivascular epithelioid cell tumor and immunotherapy considered for recurrent or metastatic patients. Future phase II/III studies in this disease should focus on sequencing of surgery and immunotherapy with a design of curative intent.

Perivascular cell-derived extracellular vesicles stimulate colorectal cancer revascularization after withdrawal of antiangiogenic drugs.

Antiangiogenic tyrosine kinase inhibitors (AA-TKIs) have become a promising therapeutic strategy for colorectal cancer (CRC). In clinical practice, a significant proportion of cancer patients temporarily discontinue AA-TKI treatment due to recurrent toxicities, economic burden or acquired resistance. However, AA-TKI therapy withdrawal-induced tumour revascularization frequently occurs, hampering the clinical application of AA-TKIs. Here, this study demonstrates that tumour perivascular cells mediate tumour revascularization after withdrawal of AA-TKI therapy. Pharmacological inhibition and genetic ablation of perivascular cells largely attenuate the rebound effect of CRC vascularization in the AA-TKI cessation experimental settings. Mechanistically, tumour perivascular cell-derived extracellular vehicles (TPC-EVs) contain Gas6 that instigates the recruitment of endothelial progenitor cells (EPCs) for tumour revascularization via activating the Axl pathway. Gas6 silence and an Axl inhibitor markedly inhibit tumour revascularization by impairing EPC recruitment. Consequently, combination therapy of regorafenib with the Axl inhibitor improves overall survival in mice metastatic CRC model by inhibiting tumour growth. Together, these data shed new mechanistic insights into perivascular cells in off-AA-TKI-induced tumour revascularization and indicate that blocking the Axl signalling may provide an attractive anticancer approach for sustaining long-lasting angiostatic effects to improve the therapeutic outcomes of antiangiogenic drugs in CRC.

Addition of Antiestrogen Treatment in Patients with Malignant PEComa Progressing to mTOR Inhibitors.

PURPOSE: Perivascular epithelioid cell tumors (PEComa) are rare mesenchymal neoplasms. mTOR inhibitors are the most active agents in PEComa and in patients progressing to mTOR inhibitors, other available therapies have limited benefit. Preclinical evidences showed a cross-talk between the mTOR pathway and estrogen receptor signaling. This provided a rationale for adding an antiestrogen treatment in female patients becoming resistant to mTOR inhibitors. EXPERIMENTAL DESIGN: Since April 2018, female patients with advanced/metastatic PEComa progressing to mTOR inhibitors were treated with a combination of sirolimus and exemestane with or without LHRH analogue (based on menopausal status). This case series was retrospectively reviewed. Survival analyses were performed using the Kaplan-Meier method. RESULTS: A total of seven consecutive patients treated with the combination of sirolimus and antiestrogen treatment were retrospectively reviewed. Six (86%) received a combination of sirolimus and exemestane, whereas one patient (14%) received a combination of sirolimus, exemestane, and triptorelin since in premenopausal status. After a median follow-up of 13.1 months, three patients (43%) experienced a partial response, three patients (43%) experienced a stabilization of disease, and one patient (14%) had disease progression with an overall response rate of 43% and a disease control rate of 86%. CONCLUSIONS: In this small retrospective case series, the addition of antiestrogen treatment in female patients with advanced PEComa progressing to mTOR inhibitors resulted in a remarkable clinical benefit in a setting where no other options are available.

Medical treatment of advanced malignant perivascular epithelioid cell tumors.

PURPOSE OF REVIEW: Malignant PEComa are rare mesenchymal tumors characterized by genetic alterations actionable by target therapy. Indeed, they harbour loss of function of TSC1/TSC2, which lead to the activation of the mammalian target of rapamycin (mTOR) pathway, which is targetable therapeutically with mTOR inhibitors like sirolimus. A small subset of malignant PEComas instead harbor TFE3 gene fusions known to be mutually exclusive with TSC1/TSC2 loss-of-function mutations; therefore, leading to different therapeutic implication. RECENT FINDINGS: mTOR inhibitors showed a response rate around 40% with a median PFS of 9 months both in retrospective case series than in phase 2 prospective clinical trials, therefore, representing the most active therapeutic drug. Up to now, the issue is the lack of further therapeutic lines in the advanced setting. Chemotherapy has a marginal role, while some responses were reported using Vascular endothelial growth factor-Tyrosine kynase inhibitors (VEGF-TKI) inhibitors. SUMMARY: Malignant PEComas display some sensitivity to mTOR inhibitors. If progression thereto, no other drugs are available. Preclinical studies are ongoing to explore the potential combination of hormonal blockade in women and the potential use of PD1 checkpoint inhibitors.

Role of Chemotherapy, VEGFR Inhibitors, and mTOR Inhibitors in Advanced Perivascular Epithelioid Cell Tumors (PEComas).

PURPOSE: Perivascular epitheliod cell tumors (PEComas) are rare mesenchymal neoplasms for which the role of systemic treatments is not established as there are no published prospective clinical trials or sufficiently large retrospective case series. The aim of this study is to clarify the activity of conventional chemotherapy and biological agents in advanced/metastatic PEComas. EXPERIMENTAL DESIGN: This was an observational, retrospective, international study that included patients with advanced/metastatic PEComa treated with systemic therapy at 5 European sarcoma reference centers and within the Italian Rare Cancer Network. Survival analyses were performed using the Kaplan-Meier method and the Cox hazards regression models. RESULTS: A total of 53 patients were included. Cytotoxic chemotherapy regimens were active only in a small proportion of PEComas. Gemcitabine-based regimens [objective response rate (ORR): 20%, median progression-free survival (PFS): 3.4 months] seemed to have the same activity of anthracycline-based regimens (ORR: 13%, median PFS: 3.2 months). Antiangiogenic agents resulted in disease stabilization in some patients, with a number having density changes/tissue response on imaging, with an ORR of 8.3% and a median PFS of 5.4 months. mTOR inhibitors were the most active agents, with an ORR of 41% and a median PFS of 9 months. CONCLUSIONS: Our study provides data for the selection of systemic therapy in patients with advanced/metastatic PEComa: mTOR inhibitors are the most active agents. Antiangiogenics and chemotherapy with gemcitabine-based regimens or anthracycline-based regimens are options in further line, but with a lower response rate and PFS.

First pancreatic perivascular epithelioid cell tumor (PEComa) treated by mTOR inhibitor.

BACKGROUND: Perivascular epithelioid cell tumor, an extremely rare mesenchymal tumor, could be ubiquitous but rarely arises from pancreas. Surgery is considered the most appropriate treatment. Nevertheless, activation of mTOR pathway seems to be a common pathogenic event in PEComas paving the way to chemotherapy by mTOR inhibitor. METHOD: A 17 year-old man presented a hypervascular tumor of 55 mm, located in the head of pancreas without bile duct or pancreatic duct compression. RESULTS: Histopathology showed epithelioid cells with clear or focally granular eosinophilic cytoplasm with melanocytic (HMB-45, Melan-A) and myoid markers which confirmed diagnosis of PEComa. Given the absence of worrisome feature, we ruled out surgery and decided to initiate treatment with Sirolimus, an mTOR inhibitor. After 3.5 years, we showed a significant reduction in size of the tumor. CONCLUSION: This first case of pancreatic PEComa treated by mTOR inhibitor without surgery suggests a good efficiency of this therapy.

Prolonged activity and toxicity of sirolimus in a patient with metastatic renal perivascular epithelioid cell tumor: a case report and literature review.

Perivascular epithelioid cell tumor (PEComa) is a family of mesenchymal tumors. Conventional chemotherapy has little activity in this disease, but case reports are available on the activity of mammalian target of rapamycin inhibitors (e.g. sirolimus and temsirolimus). Pharmacokinetic assays of sirolimus are available as this drug has a precise therapeutic window and blood levels might be influenced by CYP3A4 polymorphisms and drug interactions. We report on a case of a patient with metastatic, progressive PEComa who started sirolimus at a dose of 5 mg/day with evidence of grade (G) 3 mucositis, G2 thrombocytopenia, and G1 leucopenia 10 days after the treatment started, in absence of concomitant medications or prohibited food assumption. Elevated sirolimus blood levels were detected (156.8 ng/ml). Sirolimus was stopped, and toxicity resolved in 5 weeks. Computed tomography scan 2 months after the treatment started showed a partial response (RECIST). After toxicity resolution, the patient restarted sirolimus at a dose of 1 mg/day, with blood levels in the range of 10-20 ng/ml. Tumor response was confirmed and maintained, and the patient is still under treatment 18 months later, with no additional adverse effects. Genetic analysis of five selected polymorphisms (rs2740574, rs776746, rs1128503, rs2032582, and rs1045642) in drug metabolism enzymes and transporters did not provide a clear explanation of the observed unusual pharmacokinetic. This case confirms the activity of mammalian target of rapamycin inhibitors in PEComa and strengthens the importance of pharmacokinetic drug blood levels monitoring in patients treated with sirolimus. In our patient, after dose adjustment, sirolimus could be restarted with a prolonged clinical benefit and no additional toxicity.

Perivascular epithelial cell tumor (PEComa) of the pancreas: A case report and review of literature.

RATIONALE: Perivascular epithelial cell tumors (PEComas) of the pancreas are rare mesenchymal tumors and, to our knowledge, only 20 cases have been reported to date. PATIENT CONCERNS: We report a 43-year-old female who presented with upper abdominal pain for 1 year. She underwent an exploratory laparotomy at a local hospital, which failed to resect the tumor. Five months later, she came to the Chinese National Cancer Center for surgery. Preoperative imaging revealed an 11.5-cm-sized mass located in the head of the pancreas. At the microscopic level, the tumor was composed of epithelioid and spindle cells possessing clear to focally granular eosinophilic cytoplasm, which grew in a nested and alveolar pattern around blood vessels. The tumor cells showed immunoreactivity for human melanoma black 45 (HMB-45), but did not express epithelial or endocrine markers. DIAGNOSES: Pancreatic PEComa. INTERVENTIONS: Pancreaticoduodenectomy, partial hepatectomy, and vascular replacement were performed. After the surgery, the patient received 4 cycles of chemotherapy. OUTCOMES: The patient is free of recurrence and metastasis 1.5 years after surgical resection. LESSONS: PEComa should be recognized as a preoperative differential diagnosis of pancreatic tumors. For treatment, removal of the tumor should be attempted, and in the case of tumors with malignant tendencies, the addition of chemotherapy should be considered.

An orbital perivascular epithelioid cell tumor in a 7-year-old boy: case report and review of the literature.

We report the case of a 7-year-old boy who presented with a swollen right eye. Magnetic resonance imaging revealed a right intraconal orbital mass with intense contrast enhancement. Incisional biopsy led to a diagnosis of perivascular epithelioid cell tumor (PEComa). Sirolimus was initiated but discontinued at the third week of treatment because the tumor had progressed. A minor regression of the tumor was seen after six cycles of systemic chemotherapy. Previously reported cases of PEComa were benign in nature, and full remission was achieved with surgical excision. In the present case the tumor was malignant and responded only slightly to systemic chemotherapy.

Malignant PEComa With Metastatic Disease at Diagnosis and Resistance to Several Chemotherapy Regimens and Targeted Therapy (m-TOR Inhibitor).

Perivascular epithelioid cell tumors (PEComas) are infrequent neoplasms with peculiar myomelanocytic differentiation. The aggressive abdominopelvic variant is rare, with only a small number of published cases. We present an additional case of this unusual variant, which showed an aggressive histologic and clinical behavior with multiple liver metastases and resistance to several therapies. We also discuss the histological and immunohistochemical profiles as well as the differential diagnosis.

Treatment of Advanced Malignant Uterine Perivascular Epithelioid Cell Tumor with mTOR Inhibitors: Single-institution Experience and Review of the Literature.

Uterine perivascular epithelioid cell tumors (PEComas) are rare mesenchymal tumors. Many have malignant behavior, and no successful treatment strategy has been established. Identification of mutations in the tuberous sclerosis 1 (TSC1) and TSC2 genes producing constitutive activation of the mammalian target of rapamycin (mTOR) pathway presents an opportunity for targeted therapy. Patients with advanced malignant uterine PEComa treated with mTOR inhibitors were identified and records were retrospectively reviewed for treatment response based on radiographic assessment. Three patients with advanced uterine PEComas underwent debulking surgery followed by mTOR inhibitor therapy; two had a complete response to therapy and disease in one patient progressed. CONCLUSION: Given the absence of effective therapies for malignant uterine PEComas, targeting the mTOR pathway is a logical strategy to pursue given the known pathobiology involving the Tuberous Sclerosis complex. Treatment of malignant uterine PEComas with mTOR inhibitors was effective in two out of three patients after surgical resection, with durable response.