1500P - Response to Chemotherapy in Solitary Fibrous Tumor

Abstract

ABSTRACT Background To report on anthracycline-based chemotherapy in a retrospective case series analysis of 45 solitary fibrous tumor (SFT) patients treated within the Italian Rare Cancer Network (RTR). Methods We retrospectively reviewed all SFT treated with chemotherapy at our Institution or within RTR since 2002, focusing on anthracyclines (i.e. doxorubicin or epirubicin), administered alone or in combination with ifosfamide. Responses to ifosfamide as a single agent were also evaluated. Pathologic diagnosis was centrally reviewed in all cases, by distinguishing typical, malignant (MSFT) and dedifferentiated (DSFT) SFT subtypes. Results Among 45 pts with SFT treated with chemotherapy, we could select 31 patients (M/F: 14/17 – mean age: 62 years - locally advanced/metastatic/adjuvant: 13/17/1 - front-line/ further line = 25/5; typical/MSFT/DSFT = 0/17/13) who received anthracycline-based chemotherapy (single agent in 6, combined with ifosfamide in 24). 28 pts are evaluable for response (adjuvant = 1; too early = 1; other = 1). Overall, best response according to RECIST was: partial response (PR) = 6 (21%), stable disease (SD) = 7, progressive disease (PD) = 15 cases. Responses were confirmed after 3 months. In 2 pts with SD, a minor dimensional response was detected. Median PFS was 4 (range 2-15) months, with 20% of patients being progression-free at 6 months. PR were found in 1/16 (6%) MSFT e 5/12 (41%) DSFT. 17 pts received high-dose prolonged-infusion ifosfamide (front-line/further line = 15/2; typical/MSFT/DSFT/not assessable = 0/11/3/3 with 2 PR (both MSFT), 4 SD, 11 PD. Conclusions Anthracycline-base chemotherapy is active in a proportion of SFT pts. However, a high response rate was observed in DFST. Comparatively, ifosfamide as a single agent has low activity. Disclosure S. Stacchiotti: Pfizer: research grant for studies in which my institution is involved; honoraria. M. Libertini: Pfizer: research grant for studies in which my institution is involved;. E. Palassini: Pfizer: research grant for studies in which my institution is involved;. B. Vincenzi: Pfizer: honoraria. A.P. Dei Tos: Pfizer: honoraria. P.G. Casali: Pfizer: research grant for studies in which my institution is involved; honoraria; advisory (compensated). All other authors have declared no conflicts of interest.