Surgical resection of retroperitoneal sarcoma

INTRODUCTION — Retroperitoneal sarcomas (RPSs) are rare cancers that represent a subset (approximately 15 to 20 percent) of all soft tissue sarcomas. In contrast to sarcomas in other body locations for which 50 to 70 histologic types exist, the most common histologic types of RPS are liposarcoma (well differentiated/dedifferentiated) and leiomyosarcoma. Rarer types can also be found, such as undifferentiated pleomorphic sarcoma, solitary fibrous tumor, and malignant peripheral nerve sheath tumor.

RPSs are typically large tumors and frequently very challenging to effectively treat. The morbidity of these tumors is primarily locoregional, although some types can also metastasize. For patients with localized disease, complete surgical resection is the mainstay of treatment and only chance for cure. The technical aspects of surgery have evolved, and only in the last two decades has complete resection been feasible and safe in the majority of patients with RPS [1]. Despite the challenging nature of RPS, with modern operative techniques and histology-driven approaches to management, survival has improved over time [2].

Non-sarcoma benign and malignant diseases can also arise in the retroperitoneal space and should be ruled out during the initial workup of patients presenting with a retroperitoneal tumor [3]. For some of these diseases, surgery may not be the primary treatment (eg, lymphoma, desmoid fibromatosis). For others, the principles of surgery discussed in this topic, which will focus primarily on RPS, may still apply; however, in some cases, the approach might be entirely different (eg, laparoscopic resection for adrenal neuroendocrine tumors). The management of these other retroperitoneal tumors is discussed in more detail elsewhere. (See "Treatment of adrenocortical carcinoma" and "Treatment of pheochromocytoma in adults" and "Peripheral nerve tumors", section on 'Schwannoma' and "Paragangliomas: Treatment of locoregional disease", section on 'General principles of locoregional management'.)

PREOPERATIVE EVALUATION — Patients with retroperitoneal sarcoma (RPS) should be referred to and treated by a surgical oncologist at a sarcoma specialist center. There are several advantages to this, including greater experience for this rare cancer, access to multidisciplinary care, and the availability of clinical trials and research protocols. Clinical outcomes are also markedly better for patients with RPS treated at specialist centers [4-7]. Although practice patterns may vary by institution, specific evaluation of the patient by a surgical oncologist with experience in soft tissue sarcoma is ideal for the best coordination of care and understanding of disease biology, the latter of which is important for appropriate decision-making before, during, and after surgery. The available data suggest outcomes are better at referral centers with a minimum volume of 10 to 12 RPS cases per year [4,8]. High-volume centers may perform double or more cases per year (eg, >24) according to one study [9].

Imaging and pathology — For surgical planning, patients should have a contrast-enhanced computed tomography (CT) scan of the abdomen. Magnetic resonance (MR) imaging may complement CT for tumors that extend into the pelvis or have possible involvement of the spine or nerve roots. In select cases, after review by a radiologist with sarcoma expertise, CT alone can support the diagnosis of RPS and even suggest the histologic type without a biopsy [10-12]. This is based on tumor characteristics (eg, fat component, suggesting liposarcoma) and the potential organ of origin (eg, inferior vena cava, suggesting leiomyosarcoma). Radiomics may further refine diagnosis including histologic type and grade based on imaging alone [13].

In most cases, biopsy is encouraged to achieve a definitive diagnosis. This is particularly important if neoadjuvant therapy is anticipated. The preferred method is a CT-guided percutaneous core needle biopsy done with a coaxial technique. Although there is the theoretical risk of tumor seeding with biopsy, the data suggest that the frequency of this is exceedingly low, and overall, the benefit of diagnostic clarity outweighs the risk [14-16]. (See "Clinical presentation and diagnosis of retroperitoneal soft tissue sarcoma", section on 'Diagnostic biopsy'.)

Importantly, RPS frequently alters the typical anatomy of the retroperitoneum (figure 1) and displaces (eg, kidney) or invades adjacent organs (eg, colon mesentery) and structures. For the surgeon, a thorough preoperative review of the available cross-sectional imaging (eg, CT, MR) is critical. This is important to anticipate the extent of tumor involvement with adjacent organs and critical structures (eg, adjacent versus encasement versus gross invasion) (image 1). In some cases, repeat imaging might be necessary for a better-quality study or additional contrast phases. Ultimately, the true extent of tumor involvement will be determined at the time of surgery.

Concurrent with surgical planning, staging should be performed with at minimum noncontrast CT of the chest. This applies to all histologic types of RPS except well-differentiated liposarcoma, which does not have metastatic potential. The risk of distant metastasis, in contrast, is high in leiomyosarcoma and grade 3 dedifferentiated liposarcoma [17,18]. If metastatic disease is definitively demonstrated by imaging, surgery should be cancelled, and the patient should be referred to a medical oncologist with expertise in sarcoma.

Positron emission tomography (PET) can also be considered for staging, although this is currently not standard practice. There is emerging interest in the utility of PET in RPS for providing prognostic information about the primary tumor itself (eg, grade) [19-22].

Determination of resectability — For patients without any evidence of distant metastasis on staging imaging studies, complete resection offers the only chance for cure. All patients with localized RPS should therefore be offered surgery unless the surgeon identifies any of the following findings on the preoperative imaging review, which would generally preclude resection:

●Diffuse peritoneal implants (sarcomatosis)

●Extensive mesenteric root or celiac artery involvement

●Extensive spine involvement

●Extensive liver hilar involvement

●Bilateral renal involvement

●Extensive major vessel involvement

Patient age and comorbidities should also be considered when determining whether to proceed with resection. In a study from a single high-volume RPS center, 12 percent of patients were deemed unresectable due to technical reasons similar to those listed above or due to comorbidities and poor performance status [23].

Consideration of nonsurgical therapies — For patients with RPS, a discussion should be carried out in the setting of a multidisciplinary tumor board to determine if there may be a benefit for nonsurgical therapies (eg, radiation, chemotherapy).  

If radiation therapy is to be given, it should be done in the neoadjuvant setting to limit toxicity (eg, to bowel that would, after tumor resection, fall into the treatment field). An alternative approach is to deliver intraoperative radiation therapy, although this is dependent on institutional practice and resources available. Retrospective data exist that suggest some benefit with radiation therapy in patients with RPS [24-26]; however, there are inherent biases in these studies, and a multicenter study demonstrated no benefit after multivariate analysis [27]. A prospective trial (ie, STRASS) showed no improvement in recurrence-free survival for RPS, in general [28,29]. However, an unplanned subgroup analysis showed a possible benefit for low-grade liposarcoma. A histologic type-specific benefit for neoadjuvant radiation therapy was also observed in the STREXIT study, which retrospectively analyzed data for RPS patients treated off trial from the same centers that enrolled in STRASS [30].

Patients with RPS who are at high risk for distant metastasis (eg, leiomyosarcoma and grade 3 dedifferentiated liposarcoma) should be considered for chemotherapy. This can be given after resection; however, there are some retrospective data to suggest that adjuvant chemotherapy offers no benefit in RPS [26,31]. If there is anticipated prolonged postoperative recovery due to the proposed extent of surgery and/or comorbidities, there may also be a delay in receiving chemotherapy. In these patients, consideration should be given for neoadjuvant chemotherapy. In a multi-institution retrospective review, the frequency of response to neoadjuvant chemotherapy was moderate and depended on RPS histologic type [32]. The response type (eg, disease progression on therapy) was strongly associated with survival. In a retrospective study, neoadjuvant chemotherapy did not seem to improve overall survival in patients with primary RPS [33]. The true benefit will be better evaluated prospectively in the STRASS2, which is ongoing [34]. In this trial, patients with high-risk, resectable RPS (dedifferentiated liposarcoma or leiomyosarcoma) are randomized to either neoadjuvant chemotherapy then surgery versus surgery alone. (See "Initial management of retroperitoneal soft tissue sarcoma".)

Medical risk assessment and optimization — If the decision is to move forward with surgery, optimization of any preexisting medical comorbidities should be done with the primary care provider and, if needed, with medical subspecialists (eg, cardiology). In particular, in anticipation of possible nephrectomy, patients who are at risk of renal insufficiency (eg, chronic hypertension, diabetes) may benefit from split renal function testing and, if needed, preoperative evaluation with a nephrologist. Malnutrition is also an important issue to recognize and optimize preoperatively to avoid the negative impact on postoperative outcomes [35,36]. (See "Overview of perioperative nutrition support", section on 'Consequences of malnutrition in surgical patients'.)

For left-sided tumors, if splenectomy is anticipated, prophylactic vaccines should be given. (See "Prevention of infection in patients with impaired splenic function", section on 'Vaccinations'.)

Other surgical specialty consultation — The surgical oncologist should be intimately familiar and comfortable with the technical aspects of surgery. If needed, referrals should be made preoperatively to other surgical specialists (eg, vascular surgery) in anticipation of a multidisciplinary surgical team approach [37].

In some patients, adjunctive procedures may also be needed (eg, intraoperative ureteral stent placement by urology) and should be arranged. (See "Placement and management of indwelling ureteral stents", section on 'Prophylactic'.)

Patient counseling — With the patient, it is very important to establish the intent and goals of surgery (eg, curative, with complete resection versus palliative, to address symptoms) with realistic expectations for potential immediate/late complications, oncologic outcome, and changes to quality of life. Patients with RPS must understand that even at experienced, specialist centers, these are still challenging surgeries.

PREOPERATIVE PREPARATION

●Anesthesia considerations – For all patients, an open discussion with the anesthesiology team should take place as these are major operations. As there can be intraoperative hemorrhage, blood products should be made available. If there is potential for significant hemorrhage, adequate intravenous access with at minimum two large-bore intravenous catheters or a central venous catheter may be appropriate. For closer hemodynamic monitoring, some patients may benefit from an arterial line. For patients with cardiac comorbidities, intraoperative transesophageal echocardiogram may be warranted. Practice patterns may vary by institution. (See "Overview of anesthesia" and "Perioperative blood management: Strategies to minimize transfusions".)

●Bowel preparation – The surgeon can consider giving preoperative bowel preparation (usually the day before surgery) in anticipation of possible colon resection, although with retroperitoneal sarcoma (RPS) surgery this is not universal or mandatory. (See "Overview of colon resection", section on 'Bowel preparation'.)

●Antimicrobial prophylaxis – Antimicrobial prophylaxis should be provided and chosen in anticipation of possible colon resection. (See "Antimicrobial prophylaxis for prevention of surgical site infection following gastrointestinal procedures in adults", section on 'Colorectal procedures'.)

●Thromboprophylaxis – Patients with RPS who undergo surgery are at risk for thromboembolism and should receive standard prophylaxis. (See "Risk and prevention of venous thromboembolism in adults with cancer".)

RESECTION OF PRIMARY DISEASE — Surgical resection has traditionally been the only potentially curative treatment for a localized, primary retroperitoneal sarcoma (RPS). The ability to perform a complete surgical resection at the time of initial presentation is the most important prognostic factor for survival [38-40]. However, it is critical for the surgeon to be able to make appropriate intraoperative decisions that balance the technical feasibility of resection and expected outcomes with an understanding of histologic type and disease biology (eg, patterns of recurrence).

Incision — For RPS, which are typically large tumors, adequate exposure is key. A midline laparotomy incision is commonly used. This offers access to the major vessels and can be combined with extensions (eg, lateral, inguinal) as needed on either side to further optimize exposure. Intraoperatively, exposure is maintained with a self-retaining retractor. (See "Incisions for open abdominal surgery", section on 'Midline incision'.)

Laparoscopic or minimally invasive approaches have been described but are generally not appropriate [41,42].

Retroperitoneal exploration — Once in the abdomen and once exposure is established, the surgeon should proceed with circumferential mobilization of the tumor while assessing for involvement of adjacent organs and structures. If possible, the surgeon should not commit (eg, ligate renal hilar vessels or transect colon) until tumor resectability is confirmed. Alternatively, for borderline resectable cases, the surgeon can approach the area in question (eg, mesenteric root) directly at the start of the operation.

Tumor resection — With rare exceptions (eg, palliation), the goal of surgery in RPS is complete resection (picture 1). Most sarcoma specialists would define complete resection of RPS as R0/R1, with ideally negative microscopic margins (R0), but with acceptance of the possibility of positive microscopic margins [43]. Given the typical large size of these tumors, an accurate pathologic assessment of all margins on the resected tumor is difficult to logistically achieve. Tumors should be removed in total (not piecemeal) without any gross disease left behind. In a retrospective review of 374 RPSs, in multivariate analysis, tumor rupture during resection significantly increased the risk of death at five years (hazard ratio 2.12, 95% CI 1.39-3.25) [44]. If the intent of surgery is curative, incomplete resection is not appropriate and is associated with inferior survival compared with complete resection and with the same survival as patients who do not undergo any surgery [38,45].

En bloc resection — If an adjacent organ/structure cannot be surgically separated from the tumor without leaving gross disease behind, it should be resected en bloc with the tumor. Preoperative review of the available imaging should help the surgeon anticipate potential scenarios for en bloc resection and prepare for these, as needed (eg, consultation with other surgical specialists). (See 'Imaging and pathology' above.)

The most common organs removed are the kidney and colon [17,38,46,47]. As an example, in a multi-institutional study of 1007 patients with RPS, nephrectomy was performed in 55 percent of cases and colectomy in 58 percent [17]. In RPS, there is no rationale for performing lymph node dissection.

The same surgical considerations apply to RPS that involves or originates from major blood vessels [48]. The need for vascular resection may be anticipated preoperatively based on imaging; however, ultimately, the decision is made intraoperatively. Major vascular resection (eg, inferior vena cava, aorta) has been shown to be feasible and safe at experienced, specialist centers [49-51]. Oncologic outcomes in patients who have undergone major vascular resection are comparable to those without vascular involvement and therefore should be done when appropriate.

For left-sided tumors, the distal pancreas and spleen may also require resection. This has acceptable morbidity, and oncologic outcomes are reasonable [52]. For right-sided tumors, in contrast, pancreaticoduodenectomy or Whipple procedure is infrequently done. In a multi-institution study, these patients were shown to often require additional organ resection. Complication rates are moderate, and oncologic outcomes are overall poor [53].

There is a paucity of data regarding the benefit of en bloc resection of limited vertebral (bony) spine, liver, or abdominal wall.

Compartmental resection — For primary disease, there is some controversy over the appropriate extent of resection when there is no obvious evidence of tumor involvement of adjacent organs/structures at the time of surgery. Some sarcoma specialists advocate extended or compartmental resection in which adjacent organs/structures are liberally resected to provide a "margin" of soft tissue around the tumor, analogous to what is done for extremity sarcomas. This surgical approach is associated with lower local recurrence rates and, for low- and intermediate-grade tumors, improved overall survival [44,54,55].

However, other sarcoma specialists have criticized these studies, pointing out their retrospective nature, inherent selection bias, and the potential for higher complication rates [56,57]. There are no prospective comparisons of compartmental versus standard (complete, en bloc) resection.

Microscopic organ involvement — To help guide decision-making for the extent of resection, the frequency of histologic evidence of tumor cell invasion as compared with tumor adherence or external compression of adjacent organs has been studied. Although there exists bias (eg, inability to assess all tumor-organ surfaces), obvious invasion occurs in only 19 to 25 percent of en bloc resected organs; this frequency varies by histologic type and is highest in dedifferentiated liposarcoma [46,58]. Ultimately, organ invasion may be more of a marker of aggressive disease biology, rather than a rationale for organ resection per se [59].

Timing and pattern of recurrence — In primary disease, the risk of recurrence is highest in the first two to three years after complete resection; however, some high-grade tumors may even exhibit very early recurrence (eg, at six months) [60]. Importantly, the pattern of recurrence is dependent on histologic type. Local recurrence is the main pattern of recurrence for well-differentiated and dedifferentiated liposarcoma, whereas distant metastasis is more common in leiomyosarcoma, and in one study, grade 3 (less so grade 2) dedifferentiated liposarcoma [17,18]. In liposarcoma, local recurrence is further nuanced by multifocality (two or more discontiguous tumors), and according to one study, recurrence may even develop in areas outside of the resection field [61]. Late recurrences (beyond five years from surgery) and multiple recurrences in the same patient are also observed in liposarcoma [61-64].

RESECTION OF RECURRENT DISEASE — The ability to achieve complete resection is lower for recurrent compared with primary disease [38,65]. Oncologic outcomes are significantly better in patients whose tumors are resected compared with those who are not resected [66-69]. As an example, in one multicenter series of 219 patients with locally recurrent retroperitoneal sarcoma (RPS), the two-year overall survival rates for those undergoing resection versus no resection were 73 and 43 percent, respectively, while at five years, overall survival rates were 43 and 11 percent, respectively [66]. Therefore, if feasible, re-resection should be considered for a patient with local recurrence.

The decision-making process to re-resect, including timing, can be complex and is ideally done in the context of a multidisciplinary tumor board by a team with specific expertise in RPS. The decision to move forward with surgery is multifactorial, very individualized, and should consider the histologic type and disease biology, potential benefit of nonsurgical therapies, as well as the morbidity of resection.

If surgery is undertaken for recurrent disease, the technical approach is like primary resection, but the surgeon should anticipate loss of natural tissue planes and adhesions from prior surgery or therapy (eg, radiation), which can add to operative time and potentially increase morbidity (eg, risk of enterotomy, injury to important structures). In some patients, especially after multiple recurrences, discrimination of the borders of the tumor from normal tissue (eg, liposarcoma versus intraabdominal fat) may also be challenging.

Clinicopathologic factors that may predict better outcomes in patients with recurrent RPS include long disease-free interval, no history of tumor rupture/piecemeal resection at the primary resection, low-grade tumors (especially well-differentiated liposarcomas), and unifocal rather than multifocal disease [66,67,69,70]. A multicenter study suggested that, in addition to these variables, details of the first surgery for primary disease (eg, number of organs resected), history of receiving radiation or chemotherapy, and age and ability to achieve complete resection at the second surgery are also important considerations [71]. In this study, six-year disease-free and overall survival were 19.2 and 54.1 percent, respectively, a median follow-up of 6.3 years from the second surgery. Repeat surgeries for multiple recurrent RPS are sometimes indicated. In these cases, outcomes are associated with time to recurrence (disease-free interval) and ability to perform resection more so than any other factor (eg, histologic type) [72,73].

For patients with recurrence of retroperitoneal liposarcoma specifically, it may also be reasonable to start with a short interval period of observation with serial imaging to assess the disease biology [74]. Data from one study suggested that the average monthly growth rate of the recurrent liposarcoma may be useful to guide selection of patients who are most likely to benefit from resection [75].

Palliative surgery — In some patients with severe symptoms from their RPS, surgery may be performed with palliative intent. Surgery can involve tumor resection, which in some instances may be incomplete (eg, debulking), or surgery may not remove any tumor at all (eg, diverting colostomy).

As the goal of surgery is symptom relief, strictly speaking, the survival outcomes are not relevant. The challenge in selecting patients for palliative resection is often in determining whether surgery will truly offer durable symptom relief (eg, pain control). For more acute issues (eg, gastrointestinal obstruction), palliative surgery can often provide immediate symptom relief; however, the benefit is typically transient [76]. For patients with known metastatic disease, an additional consideration is that recovery from major abdominal surgery and the interruption of chemotherapy may also risk disease progression at other sites.

POSTOPERATIVE CARE — Adequate incisional pain control can be provided with an epidural catheter, although this practice may vary by institution. An epidural may be particularly helpful for the upper midline portion of an incision, to improve pain control and allow for proper respiratory mechanics.

For all patients, early postoperative ambulation is encouraged. The patient's diet is advanced as tolerated.

In the subsequent few days after surgery, third spacing into the retroperitoneum becomes a potential issue. Fluid management can be more challenging in the setting of a solitary kidney for patients who underwent nephrectomy as part of their resection. (See "Overview of postoperative fluid therapy in adults".)

Overall hospital stay can vary from 3 to 5 days or extend to 7 to 10 days or longer, if there is a significant postoperative ileus and depending on presence of complications. Patients with advanced age or comorbidities may benefit from a temporary skilled nursing facility for physical rehabilitation after hospital discharge.

Enhanced recovery after surgery (ERAS) pathways are currently not standard of care in patients with RPS. In one study at a high-volume center, ERAS protocols were applied to all sarcoma patients who underwent surgery [77]. In the subset of patients with RPS and ERAS, the incidence of postoperative ileus was lower (11 versus 42 percent) and length of hospital stay was shorter (8 versus 14 days) compared with non-ERAS patients with RPS.

PERIOPERATIVE MORBIDITY AND MORTALITY — Data suggest that at sarcoma specialist centers, the incidence of major perioperative (30-day) morbidity is 16 percent for primary disease [78]. A subsequent study reported the same incidence (16 percent) for recurrent disease [79]. In a single center study from a high-volume sarcoma center, among preoperative variables associated with increased morbidity after RPS resection, low serum albumin was the only one that could potentially be modified [80].

In the immediate postoperative period (approximately 24 hours) after retroperitoneal sarcoma (RPS) resection, bleeding is the major risk and can, in some patients, be a significant issue depending on the extent of resection and operative details.

Ileus may develop due to multifactorial reasons, including prolonged length of surgery, third spacing, or high narcotic requirements. This may be a significant issue, especially for patients with recurrent disease who undergo extensive lysis of adhesions. In some patients, a brief course of parenteral nutrition is needed. (See "Postoperative ileus" and "Postoperative parenteral nutrition in adults".)

As with any other open abdominal operation, intra-abdominal fluid collections may develop that may require percutaneous drainage if clinically significant or if there is concern for abscess. If an enteric anastomosis has been performed, leak from this must be ruled out. The surgeon should also consider lymphatic, urinary, or pancreatic leak, depending upon the type of resection that was done.

The most common organs resected during RPS surgery are the kidney and colon. Considerations for these patients include:

●Renal dysfunction/failure – Nephrectomy has been shown to be overall well tolerated in patients who have undergone RPS resection [81-83]; however, in some patients with baseline diabetes or hypertension, there is potential for acute and chronic renal insufficiency. Nephrectomy may also impact the ability to tolerate nephrotoxic chemotherapy regimens (eg, ifosfamide), and patients may need additional hydration prior to intravenous contrast for follow-up surveillance imaging.

●Post-colectomy complications – Right colectomy generally does not have any lasting effects; however, patients with left colectomy may have ongoing issues with changes in bowel habits such as constipation. (See "Overview of colon resection".)

Since each RPS resection is unique, it is important to individualize the potential postoperative complications. Specific considerations may include:

●Vascular graft thrombosis – Patients who have had major vascular resection may need surveillance for graft thrombosis depending on their type of reconstruction.

●Post-pancreatectomy complications – Patients who have had pancreatic resection may develop a leak, also known as a postoperative pancreatic fistula. In addition, if a significant portion of the functional parenchyma was removed, these patients may experience enzymatic insufficiency or may even develop diabetes. (See "Surgical resection of lesions of the head of the pancreas" and "Surgical resection of lesions of the body and tail of the pancreas".)

●Incisional hernia – Patients who had very large tumors or those with tumors that involved the abdominal wall musculature may develop ventral or lateral abdominal wall hernias. When bothersome, surgical repair is warranted. In some cases, these may require complex abdominal wall reconstruction. (See "Overview of abdominal wall hernias in adults".)

For some patients, particularly those with combined multiorgan resections, potential complications may also be compounded (eg, pancreatic leak onto a vascular anastomotic suture line). In general, the surgeon should keep these considerations in mind; however, there are no data to support routine postoperative cross-sectional imaging, unless indicated by clinical suspicion.

Surgery for RPS can potentially have a major impact on quality of life in patients. In one study from a single high-volume center, global health status in patients with RPS was lower at baseline prior to surgery compared with the general population but improved at 4 months after surgery and continued to improve at 12 months [84]. Chronic neuropathic pain was found to be an important and frequent issue among those who underwent psoas muscle resection, although no clinically relevant functional impairment was detected.

FOLLOW-UP AND SURVEILLANCE — In soft tissue sarcoma, surveillance after surgery is important to detect recurrence; however, algorithms are not standardized, especially for retroperitoneal sarcoma (RPS) [85]. Recommendations from consensus guidelines are discussed elsewhere. (See "Initial management of retroperitoneal soft tissue sarcoma", section on 'Posttreatment follow-up'.)

In general, patients should get a baseline postoperative contrast-enhanced CT scan to establish lack of residual disease. Then, CT scans should be repeated every four months for two to three years, then every six months until five years, and then annually. The intensity of surveillance should be individualized to each patient with consideration of histologic type and expected risk (and patterns) of recurrence. (See "Initial management of retroperitoneal soft tissue sarcoma", section on 'Posttreatment follow-up'.)

FUTURE DIRECTIONS — Further research is needed to optimize outcomes after resection in retroperitoneal sarcoma (RPS). Recently, in the United States, there is emerging interest in "textbook outcomes" (TO) in RPS based on operative details (eg, R0/R1 resection) and recovery (eg, hospital length of stay, frequency of readmission) [86,87]. TO was achieved in 35 or 54 percent of patients with RPS depending on the cohort studied and criteria used. When achieved, TO was significantly associated with improved survival.

Overall, given the rarity of this cancer, multicenter collaboration is critical. As an example, the Transatlantic Australasian Retroperitoneal Sarcoma Working Group (TARPSWG) was formed in 2013 with the goal of collaboration to understand and develop better treatments for RPS [88-90]. Technical papers and consensus guidelines for primary, recurrent, and metastatic disease have been published [27,53,71,91-94], as well as original research studies. A monthly virtual RPS tumor board has been implemented [95]. Further global collaboration is encouraged [96].

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Soft tissue sarcoma".)

SUMMARY AND RECOMMENDATIONS

●Retroperitoneal sarcoma – Retroperitoneal sarcomas (RPSs) are rare cancers and typically large tumors that are challenging to effectively treat. Complete surgical resection is the only chance for cure. Patients with RPS should be referred to a sarcoma specialist center to take advantage of their greater experience for this rare cancer, access to multidisciplinary care, and availability of clinical trials and research protocols. Minimum threshold yearly case volumes have been established. The overall approach to treatment of a patient with RPS should be discussed at a multidisciplinary tumor board to determine if the patient may benefit from nonsurgical therapies before or after surgical resection. (See 'Introduction' above and 'Preoperative evaluation' above.)

●Preoperative imaging – For surgical planning, patients with RPS should have a good-quality, contrast-enhanced CT scan, which should be thoroughly reviewed by the operating surgeon to anticipate the extent of resection based on potential tumor involvement of adjacent organs and structures. RPS frequently alters the anatomy of the retroperitoneum, displacing or invading adjacent organs and structures. Biopsy is strongly encouraged for definitive diagnosis, and based on histologic type, staging should be performed. (See 'Imaging and pathology' above.)

●Determining resectability – Surgery is offered to all good-risk surgical candidates who have localized RPS in the absence of any of the following findings on the preoperative imaging (see 'Determination of resectability' above):

•Diffuse peritoneal implants (sarcomatosis)

•Extensive mesenteric root or celiac artery involvement

•Extensive spine involvement

•Extensive liver hilar involvement

•Bilateral renal involvement

•Extensive major vessel involvement

Ultimately, the true extent of tumor involvement and resectability will be determined at the time of surgery. Resectability must also strongly consider patient comorbidities and performance status. Anticipated quality of life after surgery should also be considered, as these are major operations. Each RPS resection is unique.

●Resection of primary disease – For resection of primary disease, the tumor is removed in total (not piecemeal), without leaving gross disease behind. Adjacent organ(s) or structure(s) that cannot be surgically separated from the tumor are resected en bloc with the tumor. The kidney and colon are the most commonly involved organs. Liberal resection of adjacent organs/structures even without obvious evidence of tumor involvement can be considered, although this is controversial and practice patterns vary by institution. The histologic type may be useful to guide decision-making for more extensive resection. (See 'Resection of primary disease' above.)

●Resection of recurrent disease – Whether to resect local tumor recurrence can be a challenging decision that should be done in the context of a multidisciplinary tumor board. The decision to move forward with surgery is multifactorial, individualized, and should consider the histologic type and disease biology, potential benefit of nonsurgical therapies, as well as the morbidity of resection. The technical approach to re-resection is like primary resection, with the anticipated challenges of reoperative surgery. (See 'Resection of recurrent disease' above.)

●Postoperative care – Postoperative care and anticipation of potential immediate/late postoperative complications is individualized based upon the extent of resection and operative details (eg, organs resected). (See 'Postoperative care' above and 'Perioperative morbidity and mortality' above.)

●Follow-up – After resection, patients with RPS should undergo a baseline postoperative contrast-enhanced CT scan to establish lack of residual disease. The intensity of imaging surveillance should be individualized to each patient with consideration of histologic type and expected risk (and patterns) of recurrence. In general, CT scans are generally repeated every four months for two to three years, then every six months until five years, and then annually. (See 'Follow-up and surveillance' above.)