What Is the Impact of Multimodal Treatment in Patients with Leiomyosarcoma of Bone? A Multicenter Study of 35 Patients with an Ultra-Rare Tumor Entity.

Simple Summary: Primary leiomyosarcoma of bone constitutes less than 0.7% of all primary malignant bone tumors. Currently, there is no consensus on whether therapeutic approaches should align with the biological characteristics seen in soft tissue leiomyosarcoma or be tailored to the bone location. The efficacy of perioperative chemotherapy for this rare tumor type remains uncertain. Our study aimed to assess various treatment modalities across multiple centers. Surgical intervention emerged as the most significant prognostic factor for patient survival in our analysis, with tumors situated axially, indicating poorer prognosis. A considerable portion of patients experienced secondary metastases. Additionally, the perioperative chemotherapy regimens administered did not correlate with enhanced survival outcomes. Hence, the efficacy of perioperative chemotherapy in bone leiomyosarcoma warrants further investigation, alongside the identification of appropriate agents for treatment. Primary leiomyosarcoma of bone (LMSoB) is extremely rare, comprising only <0.7% of primary malignant bone tumors, and is therefore considered an ultra-rare tumor entity. There is currently no consensus as to whether therapeutic strategies should be based on the biological characteristics of soft tissue leiomyosarcoma or on primary tumor localization in the bone. The use of perioperative chemotherapy and its effectiveness in this rare tumor entity remains unclear. We aimed to evaluate the impact of different treatment approaches in a multicenter setting with a total of 35 patients included. The 5-year overall survival (OS) was 74%. Patients with localized disease undergoing surgery had a significantly higher 5-year OS compared to patients who did not undergo surgical treatment (82% vs. 0%, p = 0.0015). Axial tumor localization was associated with worse event-free survival (EFS) probability (p < 0.001) and OS (p = 0.0082). A high proportion of our patients developed secondary metastases. Furthermore, the perioperative chemotherapy protocols applied to our patients were not associated with an improved EFS or OS. Therefore, the benefit of perioperative chemotherapy in LMSoB needs to be further investigated, and the choice of agents still needs to be clarified. [ABSTRACT FROM AUTHOR]