Background. Solitary fibrous tumor (SFT) is a rare variant of soft tissue sarcoma (STS). Materials and Methods. We reviewed SFT patients (pts) treated at our institution between 12/1990 and 09/2017. Results. We identified 94 pts with a median follow-up (mFU) of 4.7 years (range: 0.1–21.53). Primary sites were the chest (33%), abdomen (21.3%), brain (12.8%), and extremities (9.6%); 6.4% of pts presented with synchronous metastasis. Median overall survival (mOS) from the first diagnosis was 56.0 months (m) (0.3–258.3). Doege–Potter syndrome was seen in 2.1% of pts. Primary resection was performed in 86 pts (91.5%). Median progression-free survival was 34.1 m (1.0–157.1), and 43% of pts stayed SFT-free during FU. Local recurrence occurred in 26.7% after a mFU of 35.5 m (1.0–153.8), associated with an OS of 45.1 m (4.7–118.2). Metachronous metastasis occurred in 30.2% after a mFU of 36.0 m (0.1–157.1). OS in metastatic pts was 19.0 m (0.3–149.0). Systemic therapy was given to 26 pts (27.7%) with inoperable/metastatic disease. The most common (57.7%) upfront therapy was doxorubicin, achieving responses in 13.3% of pts with a PFS of 4.8 m (0.4–23.8). In second line, pts were treated with ifosfamide or pazopanib, the latter achieving the highest response rates. Third-line treatment was heterogeneous. Conclusion. SFT is an orphan malignancy with a highly variable clinical course and a considerable risk of local failure and metachronous metastasis. Surgery is the only curative option; palliative systemic therapy is used in inoperable/metastatic cases but achieves low response rates. The highest response rates are seen with pazopanib in second/third line.

e22522 Background: Solitary fibrous tumor (SFT), a rare variant of soft tissue sarcoma (STS), is characterized by the presence of a NAB2-STAT6 fusion. Given the orphan character of SFT we performed a retrospective analysis. Methods: We retrospectively reviewed all patients (pts) with SFT treated in our institution between 12/1990 - 09/2017. Results: We identified 94 SFT pts (incl. hemangiopericytoma) with a med. follow-up for 4.7 yrs. Common anatomic sites were chest (33%), abdomen (21.3%), brain (12.8%) and extremities (9.6%). The symptomatology at diagnosis was variable. Only 6.4% presented with synchronous metastasis. Hypoglycemia (Doege-Potter syndrome) was seen in 2.1% of cases. A resection of the primary SFT was done in 86 pts (91.5%), their disease-free survival was 35.5 mo and 43% stayed SFT-free during follow-up. Local recurrence occurred in 26.7% of cases, associated with a med. overall survival (OS) of 45.1 mo. Metachronous metastasis was seen in 30.2% of pts, occurring after a med. follow-up of 36 mo. Med. OS after diagnosis of metastasis was 19.0 mo. Systemic therapy was given to 92.9% of pts with inoperable/metastatic disease. The most common 1st line therapy was doxorubicin single agent (57.7% of pts), achieving responses in 13.3% of pts. 2nd line therapies included ifosfamide and pazopanib (31.3% of pts each), 3rd line treatment was very heterogeneous. Conclusions: SFT is an orphan malignancy with a variable clinical course, low incidence of distant spread at first diagnosis but considerable risk of local failure and metachronous metastasis. Surgery is the only curative option at diagnosis, time of relapse and in case of resectable metastasis. Palliative systemic therapy is considered in pts with inoperable/metastatic disease but achieves low response rates. The natural course and survival outcomes of SFT cases treated with palliative intent tend to be better than in non-selected STS pts.

<b><i>Introduction:</i></b> Patients with metastatic soft-tissue sarcoma generally have a poor prognosis. Although chemotherapy is associated with improved overall survival in these patients, long-term benefit is rare. <b><i>Case Report:</i></b> We report on 2 patients with metastatic soft-tissue sarcoma who achieved a complete response to chemotherapy, without any local therapy, and had no signs of disease progression more than a decade after discontinuing treatment. <b><i>Conclusion:</i></b> These observations highlight the potential benefit of chemotherapy in a disease that is often considered to be poorly responsive to this treatment. These observations support further efforts to identify factors to guide patient selection and treatment optimization.

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