Comprehensive adjuvant treatment of retroperitoneal tumors The clinical evaluation and treatment of patients with soft tissue sarcomas remains a challenge for physicians, and the aggressive treatment approach of experienced multispecialty oncology teams has greatly improved the understanding of these patients since the early 1980s. The multispecialty team should include surgeons, oncologic radiologists, medical oncologists, pathologists, radiologists, rehabilitation therapists, oncology nurses, and social workers. Because of the low incidence of retroperitoneal tumors, these patients should be managed at a medical center with experience in the management of sarcomas. Each clinician involved should have an ongoing in-depth understanding of soft tissue sarcomas and their biological behavior so that patients can be evaluated, diagnosed, and initiated on ideal treatment in a timely and appropriate manner. Section I. Chemotherapy of retroperitoneal tumors Treatment of retroperitoneal tumors should be based on surgical resection, but in recent years, chemotherapy is becoming one of the means of comprehensive treatment of retroperitoneal tumors due to the continuous development of chemotherapy techniques and the emergence of new chemotherapeutic agents. The sensitivity of chemotherapy varies greatly depending on the origin of retroperitoneal tumor tissues. The methods of chemotherapy for retroperitoneal tumor include neoadjuvant chemotherapy, that is, for those who have large metastases and are difficult to be completely resected, preoperative chemotherapy is performed to shrink the tumor and achieve the purpose of surgical resection. For those who have been resected by surgery, postoperative adjuvant chemotherapy can be given to remove residual tumor in the body on the one hand, and prevent or delay tumor recurrence on the other hand. For those who have lost the chance of surgery or metastasis recurrence after surgery, palliative chemotherapy is feasible. According to the situation of retroperitoneal tumor lesions, the route of chemotherapy administration is selected, which mainly includes systemic intravenous administration, arterial local administration and abdominal chemotherapy, etc. The latter two routes can make the local lesions reach higher drug concentration in a short time, which is more suitable for patients with larger local lesions and less systemic metastases. Systemic intravenous administration can be used for preoperative and postoperative adjuvant chemotherapy, but its efficacy is not ideal for retroperitoneal tumors, and its systemic toxicity is relatively large. Arterial local administration is mostly used for patients with large tumor lesions that are difficult to be surgically resected before surgery, and this method can make the tumor lesions shrink rapidly and strive for the chance of surgical resection, and the systemic toxicity is less. Intraperitoneal chemotherapy is suitable for tumor patients whose tumors are confined to the abdominal cavity, with rapid local growth and sensitive to chemotherapy, and also for those whose tumors have been widely spread or planted in the abdominal cavity at the time of surgery and not completely removed by surgery. Since most patients do not have ascites, it is necessary to choose suitable drugs for intraperitoneal chemotherapy, avoiding drugs with high irritation, and make sure to give sufficient liquid dilution to avoid high local irritation. In addition, the number of doses should not be excessive to avoid aggravating intestinal adhesions and leading to intestinal obstruction. Our experience is to choose high-dose cisplatin (100-150 mg/dose) and to administer 1,500-2,000 ml of saline intraperitoneally each time, once a week for a total of 2-4 times. There are many chemotherapeutic agents that are effective for retroperitoneal tumors, such as vincristine (VGR), vincristine (VLB), vincristine (VDS), cyclophosphamide (CTX), isocyclophosphamide (IFO), adriamycin (ADM), cisplatin (DDP), carboplatin (CAB), methotrexate (MTX), azulfiramycin (DTIC), and vincristine (KSM). Among them, the most effective and commonly used chemotherapeutic agents as single agents are IFO, ADM, DTIC, VDS, etc. Chemotherapy regimens differ for different tissue types of retroperitoneal tumors. For malignant teratoma and germ cell tumors, drugs such as DDP+ADM+CTX are usually chosen, for malignant lymphoma, drugs such as VCR+ADM+CTX+prednisone are usually chosen, while for malignant mesothelioma, rhabdomyosarcoma and synovial sarcoma, IFO+ADM+CAB or VDS are mostly chosen.