Rechallenge with trabectedin in patients with locally advanced or metastatic soft tissue sarcoma following drug holiday: The experience of the French Sarcoma Group (FSG).

Abstract

10062 Background: Trabectedin (T) is a marine-derived alkaloid used to treat advanced soft tissue sarcomas (STS) after ifosfamide and/or anthracyclins failure. Since then, the FSG evaluated the clinical benefit in re-administrating T after an initial hold, either medically indicated or upon patient’s request. Methods: Following an online request, clinical and histopathological data were collected from six centers of the FSG who declared to have rechallenged patients. Baseline data were collected and analyze will be used. Results: From 1999 to 2011, 49 pts with T drug holiday have been identified (26 male/ 23 female), with a median age of 50 y [23-75]. Most frequent histotypes were: myxoid liposarcoma (18, 36.7%), leiomyosarcomas (13, 26.5 %) and well-differentiated/dedifferentiated liposarcoma (9, 18%). WHO grade were 1 in 14 (29%), 2 in 19 (39%) and 3 in 5 (10%) pts respectively. Patients who had a maximum of 2, 3 or 4 therapeutic sequences (TS) with T (drug-holiday and rechallenge) were 41/49 ,7/49 and 1/49 respectively. Median number of cycles for 1, 2, 3 and 4 TS were 7 [3-21], 6 [2-30], 6 [2-9] and 6. Median total number of cycles was 15 [6-43]. Median duration of drug-holiday for 1, 2 and 3 TS were 11 [3-91], 7 [2-29] and 4 months [1-5]. Grade 3-4 toxicities incidence decreased with the number of TS (occurred in 36%, 29%, 14% and 0% of pts with 1, 2, 3 and 4 TS) as well as mean T dose per cycle (1.3 mg/m², 1.2 mg/m², 1.1 mg/m² and 1.1 mg/m² for TS 1, 2, 3, 4). Efficacy decreased with number of TS (Number of CR/PR/SD/PD were 1 (2%)/15 (31%)/33 (67%)/0 for TS1; 0/4 (8%)/29 (59%)/16 (3%) for TS2; 0/1 (14%)/2 (29%)/4 (57%) for TS3 and 0/0/0/1(100%) for TS4). Median overall survival was 5.0 y [2.7-7.3] since T introduction, and 1.5 y [0.1-4.8], 0.8 y [0.5-1.3] and 0.6 y following 2nd, 3rd and 4th T reintroduction respectively. Objective response after TS2 were seen in 4 cases of grade 1 sarcomas. Conclusions: Due to the lack of cumulative toxicities over time with T, its rechallenging in responding patients to T (no progression under T) have to be considered in advanced STS.