To investigate the safety and efficacy of preoperative IMRT and concurrent Apatinib for primary truncal or extremity soft tissue sarcoma; To investigate the Quality of life and extremity function post-combination treatment; To study the mechanism of radio-sensitizing effects of Apatinib for primary truncal or extremity soft tissue sarcoma; To assess the relationship between the MRI imaging, pathological findings and local control.

Inclusion Criteria:

• Age older than 18-yo.
• Histology proven soft tissue sarcoma of truncal or extremity, deemed appropriate for preoperative radiotherapy and conservative surgery by multidisciplinary discussion.
• ECOG 0-3
• Histology reviewed by reference pathologist
• Lesion can be assessed
• Can tolerate radiotherapy and Apatinib
• Agree contraception.
• Informed consent: All patients must sign a document of informed consent indicating their understanding of the investigational nature and risks of the study before any protocol related studies are performed

Exclusion Criteria:

• No gross tumor post-resection in other center.
• Contraindications to Apatinib, including allergic to Apatinib, active bleeding, ulcer, enteric perforation, enteric obstruction, uncontrolled hypertension, Grade 3 to 4 cardiac insufficiency (per NYHA criteria), and severe hepatic or renal insufficiency (Grade 4), etc.
• Dermatofibrosarcoma protuberans(DFSP), Desmoids, etc.
• Benign histology
• Secondary cancer within 5 years (except cervical carcinoma in situ or early-stage skin basal cell carcinoma)
• STS can be cured by extensive operation alone.
• Previous irradiation to the same area
• radiological evidence of distant metastases
• Other contraindications, can't tolerate operation or other treatment needed in this study.
• Neoadjuvant chemotherapy given or planned.