81P Systemic therapy for advanced synovial sarcoma: Real-world evidence from a reference center

Limited progress has been made in the treatment of advanced soft tissue sarcoma (STS) in the last 20 years, and chemotherapy (chth) remains the backbone of therapy in metastatic settings. Considering the rarity of each STS subtype and the heterogeneity of responses to available treatment regimens, real-world data constitutes a valuable source of evidence. In this study, we aimed to describe the pattern of care and outcomes for patients with advanced synovial sarcoma. This is a retrospective analysis of patients with advanced or metastatic sarcoma treated with systemic therapies (+/- local therapy). Patient and tumor characteristics were collected from electronic records at MSCNRIO in Warsaw, Poland. Between 1 January 2000 to 31 December 2021 134 patients (49.3% females) were included. The median age was 41.6 years (16-90). The majority, 88.1%, underwent curative surgery for the primary disease, and 84.7% of them received perioperative chth. Distant metastases were present at diagnosis in 44 patients (32.8%). The median time from diagnosis to systemic therapy was 18.3 months. Median number of lines was 3 (1-8). Median PFS and OS in 1st line were 7.8 (95%CI 7.0-8.6) and 22.3 (95%CI 19.9-24.7) months, respectively. The most common chth in 1st line was high-dose ifosfamide in 65.7%, followed by doxorubicin-based regimens in 29.9%, but no differences in PFS were observed between both regimens (8.7 vs 7.0 months, p=0.735) in the overall population. 52.2% of patients underwent surgery in 1st line, which resulted in improved PFS (19.9 vs. 4.2 months, p<0.001). Among patients without local therapy, ifosfamide-based chth was more effective than doxorubicin (6.0 vs. 2.9 months, p=0.012). Median PFS in 2nd and 3rd lines were 3.5 and 3.0 months, respectively. In further lines, pazopanib was the most active drug, with a median PFS of 5.1 months. Disease control as best response was achieved in 65.7% of patients in 1st line and 34.6% in 2nd line. Our study confirmed observations from previous studies about the role of local therapy and the activity of ifosfamide-based chth in patients with advanced synovial sarcoma. The activity of systemic therapy in 2nd and next lines is very limited, with some activity of pazopanib and rechallenge with ifosfamide.