Breast desmoid tumor management in France: toward a new strategy.

Desmoid tumors (DTs) are rare tumors that originate from myofibroblastic tissue. Recently, initial wait and see was recommended (ESMO guidelines Ann Oncol 2017) in the most frequent locations. This study investigates the outcome of breast desmoid tumor (BDT) according to the initial strategy. Data from all consecutive patients treated from a BDT in four referral centers were collected. Only intra-mammary desmoid tumors were included. A pathological review and a molecular analysis (CTNNB1 gene mutation) were performed (National re-reading network of sarcomas-RRePS). Patients were grouped according to initial strategy: surgery group (SG) and active surveillance group (ASG). A total of 63 patients (61 women, 2 men) met the inclusion criteria. Median age was 50 years (16-86). CTNNB1 mutation was found in 61% (n = 36). SG included 46 patients (73%) (41 partial mastectomies, 2 mastectomies, and 3 mastectomies associated to parietectomies). Surgical margins were positive in 15 patients (33.3%). Median follow-up of SG was 24.9 (0.5-209) months; and 4 patients (8.7%) developed recurrence. ASG included 17 patients (27%). Their median follow-up was 42.2 (0-214) months, and 15 patients (88.2%) did not require any additional treatment. Six patients (35%) had a spontaneous regression, 9 patients (52%) were stable, and 2 patients presented a significant progression that was treated by partial mastectomy. This study supports an initial nonsurgical approach to BDTs followed by surgery based on tumor growth in select cases, which is consistent with current ESMO recommendations.