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% [100-100] 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.