Abstract 5876: Treatment patterns among metastatic SS patients in The US Oncology Network
Authors: Pokras Shibani , Tseng Wan-Yu , Espirito Janet , Beeks April , Carroll Charlotte , Culver Ken , Nadler Eric 
Published: June 2022

Abstract
Objective: Synovial sarcoma (SS) is a rare sub-type of soft tissue sarcoma with limited natural history documented. The study objective was to describe characteristics and treatment patterns of metastatic SS (mSS) patients receiving systemic treatments.
Methods: This was a retrospective observational cohort study in mSS patients treated in The US Oncology Network practices. Both EHR and chart review data from 2012-2019 were used. All mSS adult patients initiating systemic treatment as first-line (1L) therapy, with &gt;2 visits were included. Patients diagnosed with or treated for other primary tumors were excluded. Demographic and clinical characteristics were reported based on index date (date of first systemic treatment initiation in the metastatic setting). Time to treatment discontinuation (TTD) and time to next treatment (TTNT) were assessed using the Kaplan-Meier method.
Results: 39 adult mSS patients were identified receiving 1L systemic treatment. Of these, 25 went on to receive a 2L treatment (64%), and 16 went on to receive 3L+ treatment (41%) during the study observation period. Median age was 41.0 years, 74% male, 70% Caucasian. 25% had metastatic disease at original diagnosis of SS (vs. localized disease). 87% had metastases to lung, 25% had &gt;1 site of metastasis. See Table 1 for treatment distributions by line and for TTD and TTNT.
Conclusions: This study provides information on treatment patterns for mSS patients treated across multiple institutions within a US community oncology setting. About 2/3 of mSS patients received 2L systemic treatments. While doxorubicin and ifosfamide regimens were most common in 1L, variability exists in the 2L and onward settings, with ifosfamide and pazopanib being more frequently used than in earlier lines. Additionally, shorter TTD and TTNT with each subsequent line of therapy documents the need for effective treatment options in the 2L+ setting that can further delay progression.
Funding: GSK [208280]
Distribution of treatments by line Median time to discontinuation in months(95% CI) Median time to next treatment in months(95% CI) 1L systemic treatment (n=39) Doxorubicin + Ifosfamide containing regimen 14 (35.90%) 3.9 (2.2, 5.1) 9.3 (6.2, 11.1) Pazopanib alone or in combination 7 (17.95%) Docetaxel + gemcitabine 6 (15.38%) Ifosfamide monotherapy 6 (15.38%) Doxorubicin + olaratumab combination &lt;5 Other treatment regimens including gemcitabine, trabectedin, and investigational drugs (not related to SS) &lt;5 2L systemic treatment (n=25) Ifosfamide alone or in combination 7 (28.00%) 3.6 (1.5, 6.0) 6.7 (4.4, 11.1) Pazopanib alone or in combination 7 (28.00%) Doxorubicin containing regimen &lt;5 Gemcitabine alone or in combination &lt;5 Others including cisplatin containing regimen, trabectedin &lt;5 3L+ systemic treatment (n=31 among 16 patients) Chemotherapy monotherapy* 13 (41.94%) 2.7 (1.0, 3.7) 4.6 (1.5, 9.8) Pazopanib alone or in combination 9 (29.03%) Ifosfamide alone or in combination 5 (16.13%) Chemotherapy combination (other than with pazopanib or ifosfamide) &lt;5 *Includes dacarbazine, doxorubicin, pembrolizumab, nivolumab, IL-2, temozolomide, vinorelbine.1L, first-line therapy; 2L, second-line therapy; 3L, third-line therapy; IL-2, interleukin-2.Time to treatment discontinuation (TTD; in months) was calculated as the time interval between the initiation of each line of therapy and the last administration of that line, if there was a record of discontinuation, death or movement to the next treatment, or last administration date of the treatment if ≥120 days before the last visit date. Otherwise, patients were censored on the last administration date.Time to next treatment (TTNT; in months) was calculated as the interval between systemic treatment initiation for a given line and initiation of the next systemic treatment. Patients who did not initiate a next treatment or did not die during the study observation period were censored on the study end date, or the last visit date available in the dataset, whichever occurred first.
Citation Format: Shibani Pokras, Wan-Yu Tseng, Janet Espirito, April Beeks, Charlotte Carroll, Ken Culver, Eric Nadler. Treatment patterns among metastatic SS patients in The US Oncology Network [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5876.