Version May 2024
INTRODUCTION — Sarcomas are malignant tumors that arise from skeletal and extraskeletal connective tissues. Most soft tissue sarcomas (STS) present in the extremities, but many other sites can be affected, including the retroperitoneum, chest wall, head and neck, and subcutaneous tissues.
Retroperitoneal STS (RPS) are rare, typically large tumors that are challenging to effectively treat. For this reason, treatment should be carried out in a sarcoma center of excellence. Multidisciplinary evaluation from surgical oncology, medical oncology, and radiation oncology is also necessary to optimize clinical outcomes [1-4]. Management strategies differ across clinical institutions and treatment guidelines [5-9]. Clinical trial enrollment is strongly encouraged, where available, given the rarity of this disease and limited high-quality data on the optimal treatment approach.
The initial management of primary RPS is discussed here. The clinical presentation and diagnosis of RPS and the management of locally recurrent RPS are discussed separately:
●(See "Clinical presentation and diagnosis of retroperitoneal soft tissue sarcoma".)
●(See "Management of locally recurrent retroperitoneal sarcoma".)
PRETREATMENT EVALUATION — For patients with a confirmed pathologic diagnosis of RPS, the pretreatment evaluation should include:
●Staging imaging studies – (See "Clinical presentation and diagnosis of retroperitoneal soft tissue sarcoma", section on 'Imaging studies' and "Clinical presentation, histopathology, diagnostic evaluation, and staging of soft tissue sarcoma", section on 'Radiographic studies'.)
●A full preoperative evaluation – This includes determining resectability, medical risk assessment and optimization, multidisciplinary evaluation, and patient counseling. Further details are discussed separately. (See "Surgical resection of retroperitoneal sarcoma", section on 'Preoperative evaluation'.)
DETERMINING RESECTABILITY — The initial management of primary RPS is mainly based on resectability, which is defined as follows (see "Surgical resection of retroperitoneal sarcoma", section on 'Determination of resectability'):
●Resectable disease – Patients without the following findings on preoperative imaging studies who are anticipated to achieve a complete resection (see 'Resectable disease' below):
•Peritoneal implants (sarcomatosis)
•Bilateral renal involvement
•Extensive spine involvement
•Extensive mesenteric root involvement
•Extensive liver hilar involvement
•Extensive major vessel involvement
●Borderline resectable disease – Patients with resectable disease who are anticipated preoperatively to have gross residual disease with immediate surgery (R2 resection). In most cases, the residual tumor frequently abuts structures or organs that cannot be easily or safely resected, such as major blood vessels. (See 'Borderline resectable disease' below.)
●Unresectable or metastatic disease – Patients who do not meet the criteria for resectable or borderline resectable disease. (See 'Unresectable or metastatic disease' below.)
RESECTABLE DISEASE
Surgery — For patients with localized primary RPS, resectable disease, and no evidence of distant metastases on staging imaging studies, surgery with macroscopic complete resection provides the only opportunity for cure [9-11]. Complete resection of RPS is typically defined as either R0 (negative surgical margins) or R1 (positive microscopic margins). R1 resections are accepted as a form of complete resection because R0 resections, while ideal, are rarely achieved due to the large size and anatomic complexity of these tumors. Further details on the surgical resection of RPS are discussed separately. (See "Surgical resection of retroperitoneal sarcoma".)
Preoperative RT
Rationale for select histologies — There is no clear role for radiation therapy (RT) in the vast majority of patients with resectable RPS.
For select patients with resectable disease and select histologies at high risk for local recurrence (well-differentiated liposarcoma and low-grade dedifferentiated liposarcoma), we suggest preoperative (ie, neoadjuvant) RT plus surgery rather than surgery alone, as data suggest a reduced risk of locoregional recurrence with this approach. However, surgical resection alone is an appropriate alternative, as randomized trials evaluating preoperative RT have failed to demonstrate an overall survival (OS) advantage over surgery alone. As clinical management of these tumors is variable among institutions, shared treatment-decision making with the patient is warranted, regardless of the chosen approach. The difficulty of these clinical situations merit discussion with multidisciplinary experts at a sarcoma center of excellence who have the greatest experience with these diagnoses. (See 'Surgery' above and "Surgical resection of retroperitoneal sarcoma".)
Preoperative RT has proven benefit in STS of the extremities and truncal wall, leading to interest in evaluating its efficacy in localized RPS (see "Overview of multimodality treatment for primary soft tissue sarcoma of the extremities and superficial trunk", section on 'Choosing between preoperative and postoperative RT'). In patients with resectable RPS, data from observational studies [12-24] and early phase clinical trials [21-23] initially suggested a lower recurrence rate with preoperative RT as well as an acceptable toxicity profile [21-23,25,26]. In a randomized phase III trial (EORTC-62092; STRASS I), the addition of preoperative RT to surgery failed to improve locoregional control (abdominal recurrence-free survival [aRFS]) or OS for all patients with treatment-naïve RPS [25]. However, subgroup analyses suggest possible improved locoregional control in select histologies (eg, liposarcoma) and low-grade tumors.
In the STRASS trial, 266 patients with previously untreated localized primary RPS that was both operable and suitable for RT were randomly assigned to either surgery alone or preoperative RT followed by surgery [25]. Patients who were anticipated to have an incomplete (R2) resection were ineligible for enrollment. RT was administered as 50.4 Gy in 28 daily fractions using either three-dimensional conformal RT or intensity-modulated RT (IMRT). Histologic subtypes included leiomyosarcoma (n = 38), well-differentiated liposarcoma (n = 88), dedifferentiated liposarcoma (n = 105), other liposarcoma (n = 5), and other histologies (n = 29). Abdominal recurrence was a composite endpoint defined by one of the following events: local (abdominal) or distant progressive disease during preoperative RT, tumor or patient becoming inoperable, peritoneal metastasis found at surgery, macroscopic residual disease left at surgery, or local relapse after a macroscopically complete resection.
At a median follow-up of 43 months, the addition of preoperative RT to surgery failed to improve aRFS (median 4.5 versus 5.0 years, HR 1.01, 95% CI 0.71-1.44) or OS (five-year OS 77 versus 79 percent, hazard ratio [HR] 1.16, 95% CI 0.65-2.05) [25]. However, compared with surgery alone, local relapse rates were lower with preoperative RT plus surgery in the entire study population (13 versus 30 percent) and in the subgroup with liposarcoma (11 versus 30 percent). Furthermore, in an exploratory subgroup analysis of patients with liposarcoma histologies, there was a nonstatistically significant trend towards improved locoregional control for preoperative RT plus surgery versus surgery alone (three-year aRFS 76 versus 65 percent, HR 0.62, 95% CI 0·38-1.02), which was driven mostly by well-differentiated liposarcoma. Subgroup analyses also suggested a locoregional control (aRFS) benefit for the addition of preoperative RT to surgery among low grade (HR 0.73) relative to intermediate- (HR 1.21) and high-grade (HR 1.69) disease. Treatment-related toxicity for the STRASS trial is discussed separately. (See 'Toxicity' below.)
Limitations of this study include a nonstandard definition of aRFS and lack of stratification by histology. Further follow-up of these data is also necessary, as local recurrences can develop five years or more following treatment completion.
Another cohort study (STREXIT) evaluated patients with resectable RPS treated with surgery (with or without preoperative RT) at institutions recruiting for the STRASS trial [27]. Patients enrolled in the STREXIT cohort were eligible for the STRASS trial yet chose not to enroll in it. This study included 831 patients, of which 202 were included in a propensity score-matching analysis with the 266 patients enrolled in STRASS. The effect of preoperative RT on aRFS was similar between the STRASS and propensity-matched STREXIT cohort, both in the overall population and the subgroup with liposarcoma. In a pooled analysis of the two cohorts, preoperative RT was associated with improved aRFS among the 321 patients with liposarcoma (HR 0.61; 95% CI 0.42-0.89). Well-differentiated liposarcoma and grade 1 to 2 dedifferentiated liposarcoma (n = 266) treated with preoperative RT plus surgery also demonstrated better aRFS (HR, 0.63; 95% CI, 0.40-0.97) while grade 3 dedifferentiated liposarcoma and leiomyosarcoma did not. Preoperative RT was not associated with improved OS or distant metastases-free survival.
Advantages — The advantages of preoperative RT for primary RPS include the following [28,29]:
●The gross tumor volume can be precisely defined for radiation treatment planning, and the radiation volume around the tumor can be targeted accurately during treatment.
●The tumor can displace small bowel from the radiation treatment volume, which results in less gastrointestinal (GI) toxicity.
●Preoperative RT can potentially reduce the risk of intraperitoneal tumor dissemination at the time of surgery.
●RT may be more biologically effective in the preoperative setting.
●Preoperative RT could reduce tumor burden and potentially convert an initially unresectable tumor to a resectable one [12,30].
●For select histologies at high risk of local recurrence (eg, well-differentiated liposarcoma and low-grade dedifferentiated liposarcoma), preoperative RT may improve locoregional control. (See 'Preoperative RT' above.)
Toxicity — Preoperative RT is well tolerated, with acceptable rates of acute and long-term toxicity [21-23,25,26]. In a randomized trial (STRASS) evaluating the addition of preoperative RT to surgery in resectable RPS, the most common grade 3 to 4 toxicities for RT were lymphopenia (77 percent), anemia, and hypoalbuminemia (12 percent each) [25]. Further details of this trial are discussed separately. (See 'Advantages' above.)
Preoperative RT is better tolerated than postoperative (ie, adjuvant) RT because the tumor often displaces normal retroperitoneal structures and allows for the safe and effective delivery of radiation therapy to the tumor bed with sparing of the normal structures. By contrast, adjuvant RT can cause significant toxicity in the postoperative setting since normal tissue in the tumor bed, such as the liver and bowel, prevents safe administration of RT to effective doses [31].
In one observational study, 41 patients received preoperative RT (median dose 45 Gy) followed by surgical resection. Among these patients, 23 patients also received adjuvant brachytherapy (median dose 25 Gy) [21]. Despite the relatively large radiation volume, all patients who underwent resection reported toxicity scores of grade 2 or less for acute upper GI and lower GI or pelvis radiation toxicity, based on European Organisation for Research and Treatment of Cancer (EORTC)/Radiation Therapy Oncology Group (RTOG) toxicity criteria [32]. In addition, no patients were hospitalized for acute toxicity, and there were no interruptions or discontinuation of therapy due to toxicity. In contrast, adjuvant brachytherapy to the upper abdomen was associated with substantial toxicity (eg, duodenitis and gastric outlet obstruction), which limited subsequent use of brachytherapy to the lower abdomen.
Radiation treatment planning — Due to the complexity of treatment, preoperative RT for RPS must be administered in a center of excellence in the treatment of sarcomas [33].
Preoperative RT is generally administered at a dose of 50 Gy over 25 daily fractions or 50.4 Gy over 28 fractions. RT is delivered five days a week over approximately five and a half weeks. This dosing was used in a randomized phase III trial (STRASS) and is also consistent with management guidelines on retroperitoneal sarcoma from the American Society for Radiation Oncology (ASTRO) Clinical Practice Guidelines [9].Treatment guidelines for preoperative RT for RPS, including suggested radiation target volumes and techniques, are also available from an international expert consensus group [5,9].
Dose escalation (or "dose painting") is a concept where higher doses of preoperative RT are delivered to specific areas of the tumor at high risk for having positive surgical margins. The purpose of dose escalation is to increase local control at these specific areas. We offer dose escalation in the setting of a clinical trial, after shared decision-making with the patient. It is also crucial for the surgeon and radiation oncologist to determine the high-risk dose escalation volume in a multidisciplinary fashion, as the target will vary depending on the planned surgical approach [34].
Preoperative RT with selective dose escalation was initially evaluated in 16 patients with RPS with short-term follow up [29]. A subsequent phase I/II trial is evaluating preoperative dose escalation using both IMRT and intensity-modulated photon therapy (IMPT). In the phase I portion of the trial, IMPT dose escalation up to 63 GyRBE was achieved in 11 patients with acceptable toxicity [35].
Management after preoperative RT — Surgery is typically performed four to six weeks following completion of preoperative radiation therapy (RT). Patients who complete both preoperative RT and surgery are not offered further adjuvant therapy and may proceed to posttreatment surveillance. (See 'Posttreatment follow-up' below.)
Regional hyperthermia plus preoperative chemotherapy — Another option for preoperative therapy is regional externally delivered deep-wave hyperthermia combined with systemic chemotherapy, where available (mainly Germany). This approach has not been directly compared with preoperative RT plus surgery in randomized trials.
In a phase III trial (EORTC study 62961), 341 patients with locally recurrent (n = 37), incompletely resected or resected with a surgical margin <1 cm (n = 142), or grade 2 or 3 primary STS ≥5 cm (n = 162) of the extremity (43 percent) or a nonextremity site (56 percent, with the majority in the pelvis or abdomen) were randomly assigned to four courses of systemic chemotherapy with or without regional hyperthermia, followed by aggressive local therapy (surgery and/or RT) and four additional courses of chemotherapy with or without regional hyperthermia [36]. Chemotherapy consisted of 21-day cycles of etoposide (125 mg/m2 on days 1 and 4), ifosfamide (1500 mg/m2 per day on days 1 through 4), and doxorubicin (50 mg/m2 on day 1 only), while regional hyperthermia was performed by exposing the affected body part to temperatures between 40 and 43 degrees for 60 minutes on days 1 and 4 of each chemotherapy course.
The addition of hyperthermia to chemotherapy improved the objective response rate (29 versus 13 percent), although the number of patients who had definitive tumor resection as a component of local treatment was similar (two-thirds of both groups). At a median follow-up of 34 months, the addition of hyperthermia to chemotherapy improved disease-free survival (median 32 versus 18 months) and two-year local progression-free survival (76 versus 61 percent). In subset analysis, among patients with nonextremity sarcomas, the addition of hyperthermia to chemotherapy improved two-year local progression-free survival (64 versus 45 percent), with similar OS (59 versus 57 percent).
Other preoperative approaches
●Concurrent chemoradiation – We do not offer preoperative concurrent chemoradiation in patients with RPS. Although observational studies suggest that preoperative chemoradiation with concurrent doxorubicin or ifosfamide may reduce tumor burden and facilitate surgical resection in some patients [22,37,38], the long-term clinical outcomes and safety of adding preoperative chemoradiation to surgery has not been established in randomized trials.
●Preoperative chemotherapy – The role of preoperative chemotherapy is not established, and patients interested in this approach should be enrolled in clinical trials, where available. Based on limited initial data, preoperative chemotherapy appears to be safe and occasionally induces a radiographic response, which may reduce tumor burden and facilitate resection of borderline resectable tumors [39-42]. Further randomized trials are necessary to determine long-term survival outcomes with this approach. A prospective clinical trial (STRASS-2) is investigating the addition of preoperative chemotherapy to surgery in high-grade leiomyosarcoma and dedifferentiated liposarcoma.
Postsurgical management
Complete (R0 or R1) resection — For most patients with RPS and a complete macroscopic (ie, R0/R1) resection, we suggest surveillance alone rather than adjuvant RT or adjuvant chemotherapy, as studies have not consistently confirmed an OS benefit for either approach. (See 'Posttreatment follow-up' below.)
We do not distinguish between R0 and R1 resections with respect to surveillance or subsequent management. Microscopically positive margins (R1 resections) are frequent in RPS due to the anatomic complexities of this disease. Data are mixed for whether there is a difference in prognosis for R0 versus R1 resections [11,43-48].
In patients with completely resected RPS, studies have attempted to evaluate whether adjuvant RT or adjuvant chemotherapy confers any clinical benefit. Data are as follows:
●Adjuvant RT – For patients with resected RPS, there are no randomized trials comparing surgery with and without adjuvant RT. In observational studies, OS benefits associated with adjuvant RT have been mixed, with some studies suggesting adjuvant RT is associated with improved OS [21,24,49-52], while others have failed to demonstrate an OS benefit [53-58].
RT can also cause significant toxicity in the postoperative setting since normal tissue in the tumor bed (predominantly bowel) prevents the safe administration of RT to effective doses [31]. For these reasons, most clinical practice guidelines for RPS strongly discourage adjuvant RT following complete macroscopic resection, including those from the National Comprehensive Cancer Network (NCCN) [6], the European Society for Medical Oncology (ESMO) [7], the Trans-Atlantic Retroperitoneal Sarcoma Working Group (TARPSWG) [8], and ASTRO [9].
●Adjuvant chemotherapy – We do not offer adjuvant chemotherapy to patients with resected RPS, as an OS benefit has not been established with this approach. A pooled analysis of two phase III trials failed to demonstrate an OS benefit for adjuvant anthracycline- and ifosfamide-based regimens in patients with completely resected STS [59]. Approximately ten percent of the patients enrolled in these trials had centrally located primary tumors (ie, included RPS). A subsequent meta-analysis of six observational studies also suggested that adjuvant chemotherapy was not associated with improved OS in RPS [51].
Further details on adjuvant chemotherapy in the management of STS of the extremities are discussed separately. (See "Adjuvant and neoadjuvant chemotherapy for soft tissue sarcoma of the extremities".)
Macroscopically positive margins (R2 resection) — Some patients with RPS may have gross residual disease postoperatively (R2 resection) for several reasons. First, the primary tumor may not be completely resected due to technical factors related to proximity to normal structures or organs. Second, patients with dedifferentiated liposarcoma may also have a component of well-differentiated liposarcoma. Since the well-differentiated component can resemble normal fat, it may not be appreciated as tumor by the less-experienced radiologist and/or surgeon, and therefore inadvertently not resected. (See 'Determining resectability' above.)
For patients with RPS who have had an initial R2 resection, subsequent management is complex and clinical practice is variable. For some patients in this population, we suggest re-resection, if feasible with minimal surgical morbidity. Surveillance is an appropriate alternative in other cases, such as patients with residual well-differentiated liposarcoma (due to the indolent nature of this histology) [60], and those where further disease growth would not substantially change the necessary operation. Surveillance is appropriate for patients who are ineligible for further resection, irrespective of histology. (See 'Posttreatment follow-up' below.)
Postoperative RT is discouraged in this setting due to lack of high-quality data confirming a clinical benefit and the risk of significant toxicity to adjacent normal organs and structures [31,61].
Further details on re-resection for recurrent RPS are discussed separately. (See "Surgical resection of retroperitoneal sarcoma", section on 'Resection of recurrent disease' and "Management of locally recurrent retroperitoneal sarcoma", section on 'Surgical reresection'.)
Posttreatment follow-up — We offer the following posttreatment follow-up schedule, which is consistent with guidelines from the NCCN [6]:
●For completely resected RPS, physical examination with computed tomography (CT) imaging of abdomen and pelvis every three to six months for two to three years, then every six months for the next two years, and then annually. Given that late recurrences are not uncommon with RPS, long-term follow-up for at least 10 years is mandatory.
●We also obtain a CT of the chest every three to six months for two to three years, then every six months for the next two years, and then annually. CT contrast is administered at the discretion of the radiologist. For well-differentiated liposarcomas, we typically alternate chest imaging with either a plain radiograph of the chest or a CT of the chest due to the very low risk of metastatic disease.
Surveillance guidelines are also available from other treatment groups (table 1) [62].
BORDERLINE RESECTABLE DISEASE — The management of patients with borderline resectable RPS (see 'Determining resectability' above) is controversial due to limited high-quality data, and clinical practice is variable across treatment guidelines [5-9] (see 'Determining resectability' above). In such complex cases, we refer to an expert sarcoma center for management. Clinical trial enrollment is also encouraged, where available.
UNRESECTABLE OR METASTATIC DISEASE — Patients with unresectable disease include those with peritoneal implants (sarcomatosis) or extensive tumor involvement of major retroperitoneal organs and vasculature. Specific criteria that determine resectability are discussed separately. (See "Surgical resection of retroperitoneal sarcoma", section on 'Determination of resectability'.)
Systemic therapy — Most patients with unresectable or metastatic RPS are offered systemic therapy, which is selected based on tumor histology. Further details are discussed separately. (See "Overview of the initial treatment of metastatic soft tissue sarcoma".)
Observation is an appropriate alternative to systemic therapy for patients with select indolent histologies who are asymptomatic with limited (ie, very low) disease burden, such as those with well-differentiated liposarcoma. (See "Overview of the initial treatment of metastatic soft tissue sarcoma", section on 'When to initiate therapy'.)
Palliative resection — Palliative resection with debulking (incomplete) resection or bowel bypass may be offered to select patients with unresectable disease and severe disease-related symptoms. Such surgery should only be offered to those where it has a significant chance of improving quality of life. Further details are discussed separately. (See "Surgical resection of retroperitoneal sarcoma", section on 'Palliative surgery'.)
Palliative radiation therapy — Palliative radiation therapy (RT) may be offered in select cases of unifocal or symptomatic disease.
CLINICAL OUTCOMES
Prognosis — The prognosis of patients with RPS is typically worse compared with the prognosis of STS at other sites, such as the extremities or trunk [16,48,49,52,53,58,63-65]. Recurrent disease can also occur as late as ten or more years after treatment completion. In one observational study, among patients who were disease free for at least five years after initial surgery, 40 percent recurred by ten years. Most recurrent disease is local [10,66], although approximately 20 to 30 percent of patients present with distant metastatic disease [53,67,68]. The main sites of distant metastases are the liver and lungs.
Prognostic factors — Several factors contribute to the poor outcome and high rate of recurrence. The major prognostic factors for survival are the ability to achieve a complete macroscopic (R0 or R1) resection, the presence or absence of metastatic disease, tumor histology, and tumor grade [58].
Resectability — The ability to perform a complete resection (R0/R1) as initial therapy is the most important prognostic factor for overall survival [10]. Macroscopic complete resection is the only potentially curative treatment for localized RPS.
Histology — Histology is a very important prognostic factor for RPS. Each histology is associated with their own specific pattern of recurrence (local versus distant metastases) [66,68]. For this reason, initial reports which grouped all histologies together are less informative.
Well-differentiated liposarcoma has the most favorable prognosis, as the metastatic potential of these tumors is very low (near zero). In contrast, the least favorable survival outcome is seen with leiomyosarcoma, which exhibits a high metastatic potential; this is followed by high-grade dedifferentiated liposarcoma, undifferentiated pleomorphic sarcoma, and malignant peripheral nerve sheath tumor [47,66-74]. (See "Clinical presentation, histopathology, diagnostic evaluation, and staging of soft tissue sarcoma", section on 'Prognostic factors'.)
Well-differentiated and dedifferentiated liposarcomas have the highest rates of local recurrence. In contrast, leiomyosarcomas and solitary fibrous tumors have low rates of local recurrence. Histologic grade is also an important prognostic factor [66,68].
As an example, an observational study of 1007 patients with primary resected retroperitoneal STS demonstrated the following long-term outcomes (local and distant recurrence, as well as overall survival [OS]) by histology and grade [66]:
●Eight-year local recurrence was approximately 48 percent for G1 to G2 dedifferentiated liposarcoma, 37 percent for G3 dedifferentiated liposarcoma, and 35 percent for well-differentiated liposarcoma, compared with only 10 percent for leiomyosarcoma.
●Eight-year distance recurrence was approximately 50 percent for leiomyosarcoma and 32 percent for G3 dedifferentiated liposarcoma, compared with 9 percent for G1 to G2 dedifferentiated liposarcoma and 0 percent for well-differentiated liposarcoma.
●Eight-year OS was approximately 85 percent for well-differentiated liposarcoma, 50 percent for G1 to G2 dedifferentiated liposarcoma, 45 percent for leiomyosarcoma, and 30 percent for G3 dedifferentiated liposarcoma.
Nomograms — Nomograms have been developed and validated to more accurately predict postoperative survival based upon tumor histology and grade as well as other features, including patient age, tumor multifocality, and tumor size (figure 1) [70,73,75-80]. (See "Clinical presentation, histopathology, diagnostic evaluation, and staging of soft tissue sarcoma", section on 'Prognostic tools'.)
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".)
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Basics topics (see "Patient education: Soft tissue sarcoma (The Basics)")
SUMMARY AND RECOMMENDATIONS
●General principles – Retroperitoneal soft tissue sarcomas (RPS) are rare, typically large tumors that are challenging to effectively treat. Treatment should be carried out in a sarcoma center of excellence, and multidisciplinary evaluation is necessary. Management strategies may differ across clinical institutions and treatment guidelines. Clinical trial enrollment is strongly encouraged, where available.
●Determining resectability – The initial management of primary RPS is mainly based on resectability (resectable disease, borderline resectable disease, unresectable or metastatic disease). (See 'Determining resectability' above.)
●Resectable disease
•Surgery – For patients with localized primary RPS and resectable disease, surgery with macroscopic complete resection offers the only opportunity for cure. Complete resection of RPS is typically defined as either R0 (negative surgical margins) or R1 (positive microscopic margins). R0 resections, while ideal, are rarely achieved due to the large size and anatomic complexity of these tumors. (See 'Surgery' above.)
•Preoperative RT for select histologies – Based on the available evidence, there is no clear role for radiation therapy (RT) in the vast majority of patients with resectable RPS.
For select patients with resectable disease and histologies at high-risk for local recurrence (well-differentiated liposarcoma and low-grade dedifferentiated liposarcoma), we suggest preoperative (ie, neoadjuvant) RT plus surgery rather than surgery alone (Grade 2C), as data suggest a reduced risk of locoregional recurrence with this approach. However, surgical resection alone is an equally appropriate alternative, as randomized trials evaluating preoperative RT have failed to demonstrate an overall survival advantage over surgery alone. As clinical management of these tumors is variable among institutions, shared treatment-decision making with the patient is warranted, regardless of the chosen approach. The difficulty of these clinical situations merit discussion with multidisciplinary experts at a sarcoma center of excellence who have the greatest experience with these diagnoses. (See 'Preoperative RT' above.)
-RT dose – Preoperative RT is generally administered at a dose of 50 Gy over 25 daily fractions or 50.4 Gy over 28 fractions. RT is delivered five days a week over approximately five and a half weeks. Dose escalation (or "dose painting," where higher doses of preoperative RT are delivered to specific areas of the tumor at high risk for having positive surgical margins) may be offered in the setting of a clinical trial. (See 'Radiation treatment planning' above.)
-Timing of surgery – Surgery is typically performed four to six weeks following completion of preoperative RT. (See 'Management after preoperative RT' above.)
•Postsurgical management – For most patients with RPS and a complete macroscopic (ie, R0/R1) resection, we suggest surveillance alone rather than adjuvant RT or adjuvant chemotherapy (Grade 2C). (See 'Complete (R0 or R1) resection' above.)
For some patients who have had an initial R2 resection, we suggest re-resection (Grade 2C), if feasible with minimal surgical morbidity. Surveillance is an appropriate alternative for those with residual well-differentiated liposarcoma (due to the indolent nature of this histology) and those where further disease growth would not substantially change the necessary operation. Surveillance is appropriate for patients who are ineligible for further resection, irrespective of histology. (See 'Macroscopically positive margins (R2 resection)' above.)
●Borderline resectable disease – For patients with borderline resectable disease, clinical practice is variable, and we refer such patients to an expert sarcoma center for management. Clinical trial enrollment is also encouraged, where available. (See 'Borderline resectable disease' above.)
●Unresectable or metastatic disease – For patients with unresectable or metastatic disease, options include observation for indolent histologies that are asymptomatic with limited disease burden (ie, well-differentiated liposarcoma), systemic therapy, palliative resection, and palliative RT. (See 'Unresectable or metastatic disease' above.)
●Prognosis – Major prognostic factors include the ability to achieve a complete macroscopic (R0 or R1) resection, the presence or absence of metastatic disease, tumor histology, and tumor grade. Nomograms are available to predict postoperative survival (figure 1). (See 'Prognosis' above.)
ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges Thomas F DeLaney, MD, who contributed to earlier versions of this topic review.
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