LAUSR

11061 Background: TRB is FDA approved drug for the treatment of liposarcoma (Lipo) and leiomyosarcoma (LMS). The aim of this study was to evaluate potential biomarkers associated with prolonged benefit in patients treated with TRB at our center prior to 2016. Methods: We performed a retrospective search of UW/FHCRC CASIS database to identify patients treated with TRB prior to 2016. Demographic variables and clinical variables (such as histology and treatment) were retrieved. Statistics were performed with R 3.4.1 software. Pairwise Pearson’s correlation was calculated for the # of prior chemotherapy regimens with # of TRB cycles. The Kaplan-Meir method was used to evaluate overall survival (OS). Log-rank test was conducted to compare groups in terms of OS. Results: 145 sarcoma patients treated with TRB were identified with a mean follow up of 5 years (generally on NCT01427582 or NCT01343277). Patients averaged 1.9 prior chemotherapy regimens prior to TRB (range 0-7 regimens) and received an average of 5.6 TRB doses (range 1-25 doses). Subtypes are listed on table. The # of prior regimens was negatively correlated with the # of TRB cycles that patients received (pairwise correlation coefficient = -1.77; p=0.034), suggesting that multiple prior treatment lines either made TRB less tolerable or made sarcoma less sensitive to TRB. The median OS for this heavily treated metastatic population was 0.5 years. However, patients who were able to stay on TRB for more than 5 cycles had a significantly higher OS (p=0.001). While only 23% of patients who received less than 5 cycles of TRB were alive at 5 years (95% CI: 0.15, 0.32), 53% of those who received 5 or more cycles of (95% CI: 0.39, 0.65) were alive at 5 years. Conclusions: TRB may be more effective when administered as an earlier line of therapy. Patients who are able to stay on TRB for a longer duration had a significant improvement in OS. Detailed subset analysis will be presented as will initial findings of our biomarker work. These retrospective data warrant further evaluation. Clinical trial information: NCT01427582 or NCT01343277. [Table: see text]