The most critical component of the treatment of Retroperitineal Sarcoma (RPS) remains the surgical excision, and the best chance for cure is at the time of primary surgery. Surgery should achieve a macroscopically complete excision of the tumor (R0 or R1), minimizing marginality, ideally through an en-bloc resection of all potentially involved structures as determined by careful preoperative imaging in combination with intraoperative findings.
Operative planning also includes the functional assessment of critical organs—eg, the function of each kidney. Contraindications to primary resection are believed to be bilateral renal involvement; encasement of the superior mesenteric artery, celiac axis, and porta hepatis; and spinal cord involvement.
When planning for surgery, it is paramount to take into consideration the histology of the RPS as well as its predicted behavior pattern, as these differ widely. Indeed, the largest transatlantic multi-institutional series identified histologic subtype as a predictor of patterns of local and distant recurrence. Moreover, analysis of a large, single-institution database demonstrated that histologic subtype is the strongest predictor of disease-specific death and affects both local and distant recurrence. Of greater interest, the patterns of contiguous organ involvement are also heavily dependent on histologic subtype.
In light of these data, surgeons oncologists should decide the extent of surgical resection in a multidisciplinary setting at a specialized center after review of imaging and pathology, given that the pattern of growth and prognostic risks vary broadly among the different histologic subtypes. For example, liposarcoma is the histologic subtype with the highest recurrence rate. In addition, it is the one with the least clear separation from normal retroperitoneal fat, given that the well-differentiated component of liposarcoma is virtually undistinguishable from normal fat. As a consequence, the extent of surgery should be aimed at removing all ipsilateral retroperitoneal fat en bloc with the mass at the price of sacrificing at least the ipsilateral kidney and colon and part of or the entire psoas muscle.
A staged approach can be followed in virtually all cases. The stages include:
A. Generous laparotomy, exploration, and retraction.
B. Division of the gastrocolic ligament, division of the transverse colon (plus distal ileum if on the right side), and assessment of the duodenum/head of the pancreas if on the right side, or body/tail of the pancreas and spleen if on the left side.
C. Liberation of duodenum/head of the pancreas if on the right side or body/tail of the pancreas and spleen and duodenojejunal junction if on the left side (when possible) and partial duodenal resection or pancreaticoduodenectomy (< 5% of right-sided retroperitoneal sarcomas) if on the right side or distal pancreatectomy and splenectomy if on the left (40%–50% of left-sided retroperitoneal sarcomas), when too adherent/invaded by the tumor.
D. Dissection of the inferior vena cava (IVC) if on the right side or aorta if on the left side, ligating ipsilateral renal vessels and other collaterals and dissection of the iliac vessels.
E. Peritonectomy, resection of the psoas muscle in the pelvis (plus rectal resection if on the left side) after identification and liberation of the femoral nerve (unless directly invaded) and possibly of the femoral cutaneous branch, while the genitofemoralis and ilioinguinal nerves are usually resected, as these lie between the tumor and the psoas fascia.
F. Section of the origin of the psoas major from the spine, sparing the roots of the femoral nerve and possibly the iliohypogastric nerve, liberation/resection of the costodiaphragmatic fold, and removal of the specimen.
Subcapsular liver dissection or partial hepatectomy are rarely needed for tumors located on the right side, whereas a complete liberation of the right liver lobe is usually of help. Similarly, sleeve gastrectomy or proximal gastrectomy is rarely required for tumors located on the left side. Finally, vascular resections (predominantly iliac vessels on either side and IVC on the right side) are required in 4% of cases.
Leiomyosarcoma and other rarer histologic subtypes such as solitary fibrous tumor are much more well-defined tumors. Their border can be clearly separated from retroperitoneal fat/structures. A wide resection is still required but not necessarily involving the adjacent organs if these are not clearly invaded.
Extended surgery may raise concern for added morbidity. A recent multi-institutional collaboration, however, found that a radical resection is safe and is associated with low 30-day mortality (1.8%). Severe complications were associated with increased age, transfusion requirements, and organ resection score, with a more pronounced risk in patients undergoing splenectomy and pancreatectomy and Whipple procedure.
Although major vascular resection (MVR) is associated with higher morbidity, vascular involvement does not preclude resection because it can be safely performed in specialized centers. MVR may be necessary either due to the origin of the RPS, as is the case for leiomyosarcoma of the IVC, or due to local invasion and involvement. Whereas multiple strategies for approaching MVR can be used, a good understanding of the vasculature and collaterals is critical prior to attempting resection and reconstruction, given that IVC resections are well tolerated if a good network of collaterals is present.
In essence, resection of RPS requires technical expertise in multiple sites throughout the abdominal and pelvic cavity, including the handling of large vessels. Single organ/site expertise is not sufficient. The ability to orchestrate a team of complementary surgical experts is critical to successful management of RPS patients. To minimize the risk of intraoperative and perioperative morbidity, RPS resection should be undertaken by surgical teams with expertise in specific aspects of the anatomy of the retroperitoneal space—for example, expertise in retroperitoneal autonomic and somatic nerves, the lymphatic system, paravertebral vessels, and organs of the gastrointestinal tract.
Required expertise also includes experience with additional procedures, such as full-thickness thoracoabdominal wall resection and reconstruction, diaphragmatic resection and reconstruction, major vascular resection and reconstruction, and bone resection. Surgical teams with these abilities, which may accrue from prior participation in multidisciplinary surgical teams, can achieve macroscopically complete tumor resection in the majority of patients.