Desmoid tumor (DT; other synonymously used terms: Desmoid-type fibromatosis, aggressive fibromatosis) is a rare and locally aggressive monoclonal, fibroblastic proliferation characterised by a variable and often unpredictable clinical course. Previously surgery was the standard primary treatment modality; however, in recent years a paradigm shift towards a more conservative management has been introduced and an effort to harmonise the strategy amongst clinicians has been made. We present herein an evidence-based, joint global consensus guideline approach to the management of this disease focussing on: molecular genetics, indications for an active treatment, and available systemic therapeutic options. This paper follows a one-day consensus meeting held in Milan, Italy, in June 2018 under the auspices of the European Reference Network for rare solid adult cancers, EURACAN, the European Organisation for Research and Treatment of Cancer (EORTC) Soft Tissue and Bone Sarcoma Group (STBSG) as well as Sarcoma Patients EuroNet (SPAEN) and The Desmoid tumour Research Foundation (DTRF). The meeting brought together over 50 adult and pediatric sarcoma experts from different disciplines, patients and patient advocates from Europe, North America and Japan.

Purpose: To determine the prognostic significance of histologic type in radiation-associated soft tissue sarcomas (RASs) and determine whether RASs are associated with an inferior prognosis compared with sporadic soft tissue sarcomas (STSs). Patients and Methods: One hundred thirty primary RASs were identified from 7,649 STS patients from 1982 to 2007. Multivariate analysis of clinicopathologic factors for disease-specific survival (DSS) was performed for RASs, and a multivariate analysis of radiation exposure was also performed for RASs and sporadic sarcomas. A matched-cohort analysis was performed for radiation-associated and sporadic malignant fibrous histiocytoma (MFH). Results: Most RASs were high grade (83%), deep (87%), and truncal (61.5%). The median interval between radiation therapy and RAS development was 10 years (range, 1.3 to 74 years), which varied significantly by histologic type (P = .003). The 5-year DSS was 58%, and independent predictors were size > 5 cm, margin positivity, and histologic type. Multivariate analysis of histologic types of primary, high-grade radiation-associated and sporadic STSs showed that RAS was associated with a worse DSS (hazard ratio, 1.7; range, 1.1 to 2.4; P = .007). For pleomorphic MFH—the most common RAS type—the 5-year DSS was 44% versus 66% in a matched cohort of sporadic MFH patients (P = .07). DSS was significantly worse in primary RAS malignant peripheral nerve sheath tumors (MPNSTs) compared with unmatched sporadic MPNSTs (P = .001). Conclusion: Histologic type, margin status, and tumor size are the most important independent predictors of DSS in patients with RASs. DSS in patients with primary RAS is significantly worse compared with sporadic STS independent of sarcoma histologic type.

Many women who present with desmoid-type fibromatosis (DF) have had a recent pregnancy. Long-term data about disease behavior during and after pregnancy are lacking. To investigate the possible relationship between DF and pregnancy. A cohort of women with DF and pregnancy was identified from 4 sarcoma centers. Four groups were identified: diagnosis during pregnancy (A); diagnosis after delivery (B); DF clinically evident during pregnancy (C); and DF resected before pregnancy (D). Progression/regression rates, recurrence rates after resection, and obstetric outcomes were analyzed. Ninety-two women were included. Forty-four women (48%) had pregnancy-related DF (A + B), whereas 48 (52%) had a history of DF before conception (C + D). Initial treatment was resection in 52%, medical therapy in 4%, and watchful waiting in 43%. Postsurgical relapse rate in A + B was 13%, although progression during watchful waiting was 63%. Relapse/progression in C + D was 42%. After pregnancy, 46% underwent treatment of DF, whereas 54% were managed with watchful waiting. Eventually, only 17% experienced further progression after treatment. Spontaneous regression occurred in 14%. After further pregnancies, only 27% progressed. The only related obstetric event was a cesarean delivery. Pregnancy-related DF has good outcomes. Progression risk during pregnancy is high, but it can be safely managed. DF does not increase obstetric risk, and it should not be a contraindication to future pregnancy.