84P Exploring BET inhibitors as promising agents for solitary fibrous tumor

9.0 (1.0 -21.6) for TKI.Eight pts (15%) had fertility preservation.Median follow-up was 9.6 months [95%CI: 6.6;11.9].Partial response and stable disease (SD) were observed in 28 (52%) and 21 pts (39%).Five pts (9%) had progressive disease (PD), with majority of extra-abdominal tumors and CTNNB1 mutations (4/5).38 pts (73%) had pain relief and 33 pts (77%) were able to reduce or interrupt analgesic TTT.Among pts with SD, 50% were less painful.The 1-y PFS rate was 77.5% [64.1%;93.8%]and 73.4% of pts [59.0%;91.4%]were without TTT change after 1 year.The most common side effects were diarrhea (51%), fatigue (45%) and cutaneous rash (27%).Ovarian dysfunction was reported for 9 pts.13 pts had dose reduction (24%).At the time of analysis, 34 pts (62%) are continuing Ni, 21 (38%) discontinued Ni because of PD (N5), toxicity (N8) or personal decision (N8).Conclusions: DeNi study confirms the clinical benefit of Ni with pain improvement even without tumor shrinkage.Questions remain such as TTT duration and first-line use.