Surgery is the mainstay of treatment for soft tissue sarcomas and the principles of management of retroperitoneal sarcomas do not differ significantly from those of extremity sarcomas. All retroperitoneal sarcomas are considered deep tumours (thus making useless the differentiation between superficial and deep tumours, a recognised prognostic factor for sarcoma outcomes, useless), located beneath the fascial plane, and their location often also results in a late diagnosis, with an average size of well over 10 cm at presentation. As such, the prognosis is considerably worse in view of these factors. A pre-operative biopsy is usually not required if the radiological images are consistent with a retroperitoneal liposarcoma. However, it is useful for the exclusion of other non-sarcomatous tumours, and when pre-operative treatment with radiation or chemotherapy is being considered. In a resectable lesion, surgery can be planned for and must achieve adequate margins.14The emphasis is on obtaining a wide or radical margin remains, though these margins are much harder to define. In the extremity, where a wide margin is attained by removing a rim of 1-2 cm of normal tissue and radical resection typically necessitates a compartmental resection, the retroperitoneum is less compartmentalised and structures within it are often in close proximity, if not adjacent to the sarcoma.15A contrast enhanced CT scan is critical to define the potentially involved organs, with the absence of a distinct fat plane in such cases. It is also noted that with the diagnosis of dedifferentiated liposarcoma, the normal appearing fat surrounding often times will oftentimes represent well differentiated liposarcoma and should be removed en bloc intra-operatively. Resection with a curative intent must take into account the need for functionality after the surgery. Multi-visceral resections are not uncommon, and may encompass an en bloc resection of surrounding structures such as the large or small intestine, kidney, stomach, spleen and, occasionally, the vascular structures. Resection of an involved inferior vena cava can be performed safely, and often does not require a reconstruction, especially in the face of long-standing compression by the enlarging retroperitoneal tumour, with the formation of adequately draining collateral vessels. Resection of a portion of the aorta will require reconstruction, most often with a prosthetic graft. In recurrent tumours, the planes for dissection become less distinct, and clear margins may necessitate the removal of adherent organs, as true invasion may be difficult to ascertain. It has been shown that patients with retroperitoneal sarcomas are more likely to receive a complete resection of their tumour and have improved survival if they were treated at a specialist tertiary centre, and at a hospital with a high volume of sarcoma work.
Pre-operative radiation therapy is administered by some centres in an attempt to sterilise the margins, with its proponents citing the need for a lower dosage of required radiation to the well-vascularised field and the still-present tumour obviating a need for a spacer to prevent radiation to other uninvolved organs. However, pre-operative radiation would necessitate a pre-operative core biopsy, and the issues of contamination and subsequent excision of the biopsy pathway should be considered. Post-operative radiation, in the absence of pre-operative radiation therapy, is offered to those with an involved margin and in selected patients with high grade and large tumours (extrapolated from data from extremity sarcomas), but definitive evidence has yet to be established for pre- or post-operative radiation of retroperitoneal sarcomas, in particular since radiation postoperatively will by definition lead to a greater degree of radiation to normal tissue, which is pushed out of the way in preoperative radiation treatment of a retroperitoneal soft tissue sarcoma (see below). In the event of an unresectable retroperitoneal sarcoma, down-staging can be considered with chemotherapy or radiation.
In summary, surgery is the mainstay of treatment for retroperitoneal sarcomas. Clear margins, including an intact pseudocapsule are necessary to decrease the local recurrence rates. This may necessitate en bloc multivisceral resection of organs that are adherent to the RPS.