Leiomyosarcoma and liposarcoma in young patients: The national netsarc+ network experience

Background: Leiomyosarcoma (LMS) and liposarcoma (LPS) are ultra-rare sarcomas in pediatric (0–18 years) and young adult (19−30) populations. We aimed to analyze their clinical characteristics at these young ages and to determine whether they should be considered with the same therapeutic strategy in both populations. Methods: National retrospective multicenter study of all young patients (0–30 years) included in the sarcoma database “ConticaBase”, treated for LMS or LPS between 2010 and 2019 via the national NETSARC+ network, with available pathology/biology review. Findings: A total of 218 patients were identified, 34 children (nine LMS, 25 LPS) and 184 young adults (58 LMS, 126 LPS). Myxoid/Round Cell LPS (M/RC-LPS) was the most frequent LPS subtype (72 %). All children had localized LMS and LPS, versus 52/58 and 116/126 respectively in adults. Clinical presentation of LMS and all LPS subtypes was comparable in both populations, except for a preferential limb location of LMS in children. The therapeutic strategy was mainly based on primary surgery in LMS (9/9 children, 52/58 adults) and for LPS (respectively 25/25 and 122/126), exclusively or with adjuvant radiotherapy and systemic treatment. With a median follow-up of 62.4 months (range, 2.5–146), 5-year overall survival was respectively 83 % [95 % CI, 58–100] in children and 73 % [61–88] in young adults for LMS, 100 % [100] vs 92 % [87–99] for M/RC-LPS and 25 % [5–100] vs 60 % [29–100] for pleomorphic LPS. Interpretation: LMS and all LPS subtypes appear to display comparable behavior in children and young adults. The authors propose that the same therapeutic strategy should be considered for both groups.