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8. Retroperitoneal Sarcoma (RPS)

  • Given the rarity of RPS, there isn’t high level evidence based on large randomized controlled trials to guide management. The recommendations and statements below are based on smaller prospective and retrospective cohort and case-controlled studies and expert consensus opinions.
  • Retroperitoneal sarcomas (RPS) are rare, comprising 10-15% of all STS. Patients usually present in their 50’s, although the age range is broad. These tumors affect men and women equally. 
  • Approximately 80% of retroperitoneal tumors are malignant. 
  • The majority of patients who present with a primary retroperitoneal, extra-visceral, unifocal soft tissue mass will be found to have a sarcoma.
  • The most common histologic subtypes in adults are:
    • liposarcoma, leiomyosarcoma and undifferentiated pleomorphic sarcoma.
  • Differential diagnosis: other entities that may present as retroperitoneal masses and need to be ruled out include metastatic adenocarcinoma, lymphoma, germ cell tumor and paraganglioma.
Presentation
  • RPS typically do not cause many symptoms until they are large enough to compress or invade surrounding structures. Thus, most tumors are already large (>15cm) and advanced at the time of diagnosis.
  • Local invasion or compression can lead to lower extremity edema, gastrointestinal symptoms and ascites.
  • Distant metastases (most commonly to lung and liver) can be present in about 10% of cases at the time of diagnosis.
Staging and preoperative assessment
  • CT scan of chest, abdomen and pelvis with IV contrast.
  • MRI is an option for patients with IV contrast allergy or other contraindications, or pelvic tumors, and for assessing the extent of tumors to specific sites (ie. Vertebral foramina, sciatic notch) that is not clear on CT scan. 
  • Functional assessment of the contralateral kidney is necessary for planning treatment of the ipsilateral RPS.
  • Bone scan and PET scanning do not usually add useful information to staging assessment. 
Biopsy
  • Image-guided percutaneous coaxial core needle biopsy is strongly recommended (unless the imaging is pathognomonic and no pre-operative treatment is planned.
  • Multiple needle cores should be obtained to allow for histologic and molecular subtyping. 
  • Sampling of the more solid, dedifferentiated tumor component represented by well-perfused areas in contrast (enhanced CT or MRI is strongly encouraged). 
  • The risk of needle track seeding is minimal and should not be a reason to avoid a biopsy.
  • Fine needle aspiration should be avoided as it rarely yields diagnostic information and can delay treatment.
  • Laparotomy with open biopsy and/or laparoscopic biopsy should be avoided as this exposes the peritoneal cavity to contamination by sarcoma, distorts subsequent planes of dissection, may put vital neurovascular structures at risk and may still not provide diagnostic material due to lack of 3-dimensional image guidance.
  • Patients found unexpectedly to have a retroperitoneal mass at the time of laparotomy, laparoscopy or other abdominal procedure should not undergo biopsy. Nothing further should be done at that time. The patient should undergo dedicated imaging and workup of the retroperitoneal mass. 
Surgery
  • The best chance for resection with curative intent is at the time of primary presentation. 
  • The individual management plan will take into account tumor factors (histologic subtype which determines biologic behavior, response to treatment) and patient factors (performance status, nutritional status, comorbidities).
  • Complete gross resection is the cornerstone of management.  Surgery should aim to achieve a macroscopically complete resection, with a single specimen encompassing the tumor and involved contiguous organs, and at minimizing microscopically positive margins. This is best achieved by resecting the tumor en bloc with adherent structures even if not overtly infiltrated. 
  • Surgical expertise in RPS requires specific anatomic knowledge of the retroperitoneal space to minimize the risk of intra- and peri-operative morbidity.
Adjuvant/Neoadjuvant therapy
  • Although no randomized trials of neoadjuvant therapy versus resection alone for RPS have been reported to date, neoadjuvant therapy in the form of chemotherapy, external beam radiation or combined radiation and chemotherapy is safe for well-selected patients and may be considered after careful review by a multidisciplinary sarcoma tumor board. This is particularly relevant in the case of technically unresectable/borderline resectable RPS that could potentially be rendered resectable by downsizing, and for chemo-sensitive histologies.
  • There is no study-proven value for post-operative adjuvant treatment after complete gross resection of RPS with either radiotherapy or systemic therapy.
Follow-up evaluation
  • Risk of recurrence after grossly complete resection does not plateau. Patients should be followed indefinitely.
  • The median time to recurrence of high-grade RPS is less than 5 years after definitive treatment.
  • Follow-up assessment should include cross-sectional imaging.
  • In years 1-5, follow-up evaluations should be at intervals of 3-6 months, extending to annually after year 5. 
Recurrent retroperitoneal sarcoma
  • The decision to pursue curative resection with complete gross resection is multifactorial. 
  • Histopathologic subtype should factor into the decision to pursue re-resection as response to treatment varies by histologic subtype. For example, well-differentiated liposarcoma would be favored for re-resection.
  • Other factors to consider which predict for favorable outcome are: no history of tumor rupture, low grade, long disease-free interval, and solitary recurrence. 
  • The chance of long-term disease free survival is limited despite complete gross resection of recurrent RPS.
  • For isolated locoregional recurrence, the goal of resection should be curative.
  • Multifocal intra-abdominal disease is difficult to resect completely and will almost certainly recur. 
  • In general, synchronous abdominal and distant recurrence should not be resected, and the patient should be considered for systemic therapy.
  • Neoadjuvant systemic therapy may be of benefit in downsizing recurrent disease and assessing tumor biology. 
  • Pre-operative radiotherapy should be considered if not previously given and if recurrence is isolated.
  • There is no proven role for post-operative adjuvant systemic or radiotherapy after complete resection of recurrent RPS.
  • There is no proven role for intraperitoneal chemotherapy with regional hyperthermia.
  • The management of patients who are not eligible for resection should be individualized and can include palliative systemic therapy, radiation or surgery with the intent of relieving symptoms and improving quality of life.
  • In select patients, survival with recurrent RPS may be prolonged (eg, well-differentiated liposarcoma).  The potential to live many years despite ongoing presence of disease should be recognized and adequately communicated with the patient.
References

  • Management of primary retroperitoneal sarcoma (RPS) in the adult: a consensus approach from the Trans-Atlantic RPS working group.  Ann Surg Onc 2015; 22:256-263
  • Management of recurrent retroperitoneal sarcoma (RPS) in the adult: A consensus approach from the Trans-Atlantic RPS working group. Ann Surg Onc 2016; 23:3531-3540

SOURCE: 8. Retroperitoneal Sarcoma (RPS) ( )
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