Case Report: Pazopanib Treatment Response in a Patient with Metastatic Pleomorphic Dermal Sarcoma (Atypical Fibroxanthoma) with Circulating Tumor Cell-Derived Colonies as a Predictive Marker

Abstract

Atypical fibroxanthoma s (AFX) are rare skin tumors. These generally are superficial tumors, usually <3 cm red, fleshy, ulcerated skin lesions, that characteristically occur on sun-damaged skin, sometimes in immunocompromised or previously irradiated patients. These are part of a spectrum of more aggressive fibro-histiocytic neoplasms. In the older literature, these have been termed aggressive or metastatic AFX, but currently these have been reclassified as pleomorphic dermal sarcomas (PDS) and systemic undifferentiated pleomorphic sarcoma (UPS, formerly malignant fibrohistiocytic sarcoma, MFH). We present the case of a 64-year old woman who developed a deeply invasive PDS on the vertex of her scalp invading to the galea, with in-transit scalp metastases. Very little information is available about optimal treatment of metastatic PDS lesions. The patient was initially treated with 2 cycles of epirubi cin/ifosfamide chemotherapy, resulting in life-threatening complications. A pretreatment peripheral blood sample was sent for CTC-derived colony assay. This sample grew 8 colonies from 10 ml blood. The tumor failed to respond to epirubicin and ifosfamide, and after several months of hospitalization, a second peripheral blood CTC-derived colony assay grew >376 colonies. The patient could not tolerate additional chemotherapy. She was therefore treated with the oral targeted agent pazopanib. The patient developed a dramatic biopsy-confirmed complete response. After 11 months of pazopanib treatment, a repeat CTC-derived culture sample grew only 8 colonies/10 ml blood. The complete response to pazopanib is still ongoing at over 41 months. To our know ledge, this is the first demonstration of clinical complete response of a PDS tumor following targeted therapy. An additional novel feature was the demonstration that CTC-derived colonies could be grown from the blood of a PDS patient. The number of colonies appeared to correlate with the clinical treatment response and seemed to function as a potential prognostic marker.