Functional Assays to Guide Personalized Oncological Treatment of Patients with Soft-Tissue Sarcomas

Background/Objectives: Soft tissue sarcomas (STSs) are rare tumors arising from mesenchymal tissues, comprising over 100 distinct histological subtypes with varying biological behaviors, metastatic patterns, and treatment responses Despite advances in multimodal therapy, the overall survival of patients with metastatic STS is poor, mainly due to the weak response to conventional chemotherapy based on doxorubicin and ifosfamide. Methods: This review examines the evolution from traditional one-size-fits-all treatments to personalized medicine strategies, primarily focusing on assays based on patient-derived tumor samples, and it highlights their emerging role in guiding personalized treatment decisions and improving clinical outcomes in STS. These approaches, also known as functional precision oncology, are a step closer to the clinical situation as compared to other personalized therapies that rely on the identification of targetable genomic alterations using high-throughput technologies such as whole-genome sequencing, which have thus far failed to show convincing responses in STS treatment. Results: The main functional precision oncology platforms tested in patients with STS are in vitro cell viability tests, organoid cultures, and patient-derived xenografts. Each has advantages and limitations. In this context, in vitro drug sensitivity using cell suspension or organoids has shown a strong correlation with clinical responses. Furthermore, organoids matched the original tumor histology and microenvironment to a satisfactory degree. Establishment of xenografts proved feasible in the majority of patients; the technique could also preserve the tumor architecture and displayed high physiological relevance to the clinical situation. Conclusions: Although a major clinical study directly comparing conventional chemotherapy to personalized treatment guided by functional assays is yet to be published, this approach has gained popularity given the low efficacy of personalized medicine based on genetic alterations. The results thus far show promise for a better outcome for patients with metastatic STS.