Original Article Stereotactic ablative brachytherapy with or without assistance of 3D-printing templates for inoperable locally recurrent or oligometastatic soft-tissue sarcoma: a multicenter real-world study

The management of inoperable locally recurrent or oligometastatic soft-tissue sarcoma (STS) remains a clinical challenge. This study aimed to explore the long-term outcomes of stereotactic ablative brachytherapy (SABT) for these patients. Patients diagnosed with inoperable locally recurrent or oligometastatic STS from eight hospitals between 2006 and 2021 underwent iodine-125 (I-125) seed SABT, either with or without the assistance of threedimensional (3D)-printing templates. The analysis concentrated on several key parameters, including objective response rate (ORR), disease control rate (DCR), local control time (LCT), overall survival (OS), adverse events (AEs), pain relief rate, and performance improvement rate. The ORR and DCR reached 78.3% and 95.0%, respectively. The results of multivariate logistic regression analysis indicated that a smaller tumor volume and a higher treatment dose were significantly associated with complete response (P < 0.001; P=0.036). The 1-, 3-, and 5-year LCT rates were 73.2%, 40.6%, and 37.9%, respectively. The 1-, 3-, and 5-year OS rates reached 83.1%, 50.5%, and 36.1%, respectively. Multivariate analysis revealed that a higher dose, a smaller tumor volume, and utilization of 3D-printing templates were significantly positive prognostic factors of LCT (P=0.006; P=0.007; P=0.034). Moreover, the tumor locations of trunk wall and extremities and lower tumor grade (G1/2) were significantly positive prognostic factors of survival (P=0.008; P=0.002). Pain relief rate was 88.0%, and the performance improvement rate was 46.7%. The AEs were predominantly of grade <= 2 and were well-tolerated. SABT seems to be an efficacious and safe alternative therapy for inoperable locally recurrent or oligometastatic STS.