Trabectedin failure-free survival (TFFS) after resuming trabectedin (T) in advanced myxoid liposarcoma (MLPS) patients

11573 Background: To explore the time to trabectedin failure-free survival after resumption of T in advanced MLPS patients who were stable or responding to T at the time of discontinuation. Methods: We retrospectively collected the cases of all patients with advanced MLPS treated with T at our institution from September 2002, highlighting those who were free from progression (according to RECIST) after 6 cycles of T. Trabectedin failure-free survival (TFFS) was defined as time from the first cycle of T to progression (PD) or death, whichever occurred first. Survival analyses were performed using the Kaplan-Meier method. Results: Since September 2002, 75 patients with recurrent myxoid liposarcoma received T at our institution. A total of 56 patients were free from progression (according to RECIST) after 6 cycles of T and were included in this analysis. Among them, 25/56 (45%) interrupted their treatment in absence of progression, while 31/56 (55%) patients received T until progression of disease. In the former group, 11/25 had surgery of their residual disease, 3/25 received radiotherapy, 5/25 interrupted T for toxicity and 6/25 patients shared the decision to stop with the clinician. Among patients who received surgery, 2/11 had monofocal disease (longest diameter < or = 5cm), 4/11 had monofocal disease (longest diameter between 10-18 cm) and 5/11 had plurifocal disease. The interruption of T in these 25 patients occurred after a median of 12 cycles (interquartile range = 9-14). Median TFFS was 43.4 months (95%CI 38.7-NA). In the concurrent group of patients who received T continuously, the median TFFS was 14.2 months (95% CI: 10.8-21.9). Conclusions: While the longer TFFS of patients undergoing discontinuation cannot be compared with the shorter of those who did not interrupt, the former group being biased favorably (feasibility and exploitation of surgery, other likely determinants of physician’s decision to stop), we speculate that there may be a subgroup of selected patients with advanced myxoid liposarcoma primarily responding to T, who could benefit from a “stop and go” policy, thus prolonging the overall time interval within which T remains active. Prospective studies in selected subgroups of MLPS patients on optimization of treatment strategy with T are worthwhile.