(P 267) EFFICACY OF SORAFENIB IN PRETREATED DESMOID TUMORS. EXPERIENCE OF A HIGH-VOLUME CENTER.

Objective: Desmoid tumor (DT) is defined as a monoclonal fibroblastic proliferation. However watch and wait is the first step, in rapidly progressive or very symptomatic patient, systemic treatment should be considered.
Sorafenib has been tested in DT with optimal disease control.
The objective of this retrospective study is to evaluate the efficacy of sorafenib in clinical practice and establish factors related with the response and the disease control during and after sorafenib treatment.

Methods: An evaluation of the clinical characteristic of the patients was performed. Response rate was evaluated by RECIST 1.1.
Prognostic factors like image changes (fibrosis), mutation status, symptoms control and response rate were evaluated.

Results: 22 patients were evaluated median age was 33 y, and 90% were women. In half of the patients a surgical intervention was performed at diagnosis however 60% presented tumor at first evaluation. 90% of the patients presented a mutation in betacatenine, however 2 patients presented a systemic mutation in APC. 36% of the tumor were located in extremities, 27% in thorax and 18% were intrabdominal.
80% of the patient were pretreated with almost 2 lines, including chemotherapy.
Dose reduction was performed in 7 patients. No grade 4 adverse event was presented, 30% presented G3 hiperqueratosis or mucositis, solved after dose reduction.
Median treatment duration was 15 months. 59,1% of the patient achieved a partial response and 40,9% stable disease as best response. Only 1 patient relapsed during the treatment in the context of dose reduction. Over 90% of the patients presented indirect data of fibrosis in magnetic resonance.
Symptoms control was achieved in 85% with pain reduction (visual analog scale)
12 patient stopped treatment. After a follow up of 9 months since treatment stop, only 2 patients relapse both did not achieve a partial response by RECIST criteria and fibrosis was not observed.

Conclusion: Sorafenib is a safe option with high disease and symptoms control.
After treatment stop in patients with disease control and indirect data of fibrosis, disease still remains controlled.