{"entity":{"id":"retroperitoneal-sarcoma","kind":"cancer","name":"Retroperitoneal sarcoma","aka":["Retroperitoneal soft tissue sarcoma","RPS","Abdominal sarcoma"],"tldr":"Retroperitoneal sarcomas grow silently at the back of the abdomen until they are the size of a melon. The treatment is one carefully planned operation in a sarcoma centre that removes the tumour with the neighbouring organs it touches. The STRASS trial showed radiotherapy before surgery does not help overall; a second trial is testing chemotherapy before surgery in the most aggressive types.","summary":"Retroperitoneal sarcomas are a site-defined group: well-differentiated and dedifferentiated liposarcoma make up about two thirds, leiomyosarcoma about a fifth, and solitary fibrous tumour, MPNST and undifferentiated pleomorphic sarcoma most of the rest. They present late as huge painless masses that displace the kidney, colon and pancreas, and the dominant pattern of failure differs by histology: liposarcoma recurs locally in the abdomen, often repeatedly and years later, while leiomyosarcoma metastasises to the liver and lungs. The Transatlantic Australasian Retroperitoneal Sarcoma Working Group consensus documents define the modern approach.\n\nComplete en bloc resection at first presentation, removing adjacent organs such as kidney, colon and psoas to secure a margin, is the only curative treatment and has been associated with better local control in reference centres since the reports of Gronchi and Bonvalot in 2009. Adjuvant therapies were tested in the EORTC STRASS trial, which randomised 266 patients to preoperative radiotherapy plus surgery or surgery alone and found no improvement in abdominal recurrence-free survival overall, though an unplanned analysis suggested benefit in well-differentiated and low-grade dedifferentiated liposarcoma. Preoperative radiotherapy is therefore not routine and is discussed case by case for liposarcoma.\n\nSystemic therapy is histology-driven: doxorubicin with ifosfamide for dedifferentiated liposarcoma, doxorubicin with dacarbazine or trabectedin for leiomyosarcoma (LMS-04), and eribulin and MDM2 inhibitors for liposarcoma. The STRASS2 trial is testing neoadjuvant chemotherapy against surgery alone in high-risk dedifferentiated liposarcoma and leiomyosarcoma, and repeat surgery for recurrence, selected by growth rate and multifocality, remains the main tool after relapse.","asOf":"2026-09-17","wikipedia":"https://en.wikipedia.org/wiki/Sarcoma","links":[{"label":"TARPSWG","url":"https://www.tarpswg.org"}],"tags":["subtype-page"],"related":["liposarcoma","leiomyosarcoma","sarcoma"],"cancers":[],"sections":[],"technologies":[],"targets":[],"drugs":[],"companies":[],"institutions":[],"pathways":[],"terms":[],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"group":"sarcoma","burden":"About 15 percent of soft tissue sarcomas, mostly well-differentiated and dedifferentiated liposarcoma and leiomyosarcoma, diagnosed as very large masses in the space behind the bowel; local recurrence, not metastasis, kills most patients with liposarcoma, and outcomes depend heavily on treatment in a specialist centre.","subtypes":["Well-differentiated liposarcoma of the retroperitoneum (local recurrence, no metastasis)","Dedifferentiated liposarcoma of the retroperitoneum (grade 1 to 3)","Retroperitoneal leiomyosarcoma (including inferior vena cava; distant metastasis)","Solitary fibrous tumour and MPNST of the retroperitoneum","Undifferentiated pleomorphic sarcoma of the retroperitoneum"],"biomarkers":["Histological subtype and grade on preoperative core biopsy","MDM2 amplification (liposarcoma)","Multifocality and growth rate at recurrence","Sarculator nomogram risk"],"standardOfCare":[{"setting":"Primary, resectable","approach":"Single-stage complete en bloc resection with adjacent organs in a sarcoma reference centre, after core biopsy and multidisciplinary planning; preoperative radiotherapy not routine after STRASS, considered in well-differentiated and low-grade dedifferentiated liposarcoma.","refs":["strass","imrt-igrt","ct","fnclcc-grade"]},{"setting":"High-risk dedifferentiated liposarcoma or leiomyosarcoma","approach":"Neoadjuvant chemotherapy within STRASS2 (doxorubicin-ifosfamide or doxorubicin-dacarbazine) or up-front surgery; no proven adjuvant therapy.","refs":["doxorubicin","ifosfamide","dacarbazine"]},{"setting":"Recurrent or metastatic","approach":"Repeat resection for slowly growing, unifocal recurrence; histology-driven chemotherapy (doxorubicin plus trabectedin for leiomyosarcoma, LMS-04; eribulin or trabectedin for liposarcoma); MDM2 inhibitor trials.","refs":["trabectedin","lms-04","eribulin","mdm2-inhibitors","pazopanib"]}],"stateOfArt":["STRASS settled that preoperative radiotherapy does not improve outcomes across all retroperitoneal sarcomas.","Extended en bloc resection in expert centres is the intervention with the largest effect on local control.","STRASS2 is testing neoadjuvant chemotherapy in the histologies most likely to metastasise."],"history":[{"year":2009,"title":"Gronchi and Bonvalot report improved local control with extended en bloc resection","refs":[]},{"year":2015,"title":"TARPSWG consensus on management of primary retroperitoneal sarcoma","refs":[]},{"year":2019,"title":"STRASS2 opens: neoadjuvant chemotherapy versus surgery alone","refs":["doxorubicin","ifosfamide"]},{"year":2020,"title":"STRASS: preoperative radiotherapy does not improve abdominal recurrence-free survival","refs":["strass"]}],"pipeline":["mdm2-inhibitors","eribulin","trabectedin"],"openProblems":["Liposarcoma recurs in the abdomen in most patients even after complete surgery.","Neither radiotherapy nor chemotherapy has a proven adjuvant benefit.","Outcomes still depend on referral to a specialist centre before the first operation."],"parent":"sarcoma"},"route":"/cancers/retroperitoneal-sarcoma/","neighbours":{"cancer":[{"id":"leiomyosarcoma","kind":"cancer","name":"Leiomyosarcoma","route":"/cancers/leiomyosarcoma/"},{"id":"liposarcoma","kind":"cancer","name":"Liposarcoma","route":"/cancers/liposarcoma/"},{"id":"pecoma","kind":"cancer","name":"Perivascular epithelioid cell tumour (PEComa)","route":"/cancers/pecoma/"},{"id":"sarcoma","kind":"cancer","name":"Sarcomas (soft tissue, bone, GIST)","route":"/cancers/sarcoma/"}],"drug":[{"id":"dacarbazine","kind":"drug","name":"Dacarbazine","route":"/drugs/dacarbazine/"},{"id":"doxorubicin","kind":"drug","name":"Doxorubicin","route":"/drugs/doxorubicin/"},{"id":"eribulin","kind":"drug","name":"Eribulin","route":"/drugs/eribulin/"},{"id":"ifosfamide","kind":"drug","name":"Ifosfamide","route":"/drugs/ifosfamide/"},{"id":"pazopanib","kind":"drug","name":"Pazopanib","route":"/drugs/pazopanib/"},{"id":"trabectedin","kind":"drug","name":"Trabectedin","route":"/drugs/trabectedin/"}],"trial":[{"id":"lms-04","kind":"trial","name":"LMS-04","route":"/trials/lms-04/"},{"id":"strass","kind":"trial","name":"STRASS (EORTC 62092)","route":"/trials/strass/"}],"technology":[{"id":"ct","kind":"technology","name":"CT (computed tomography)","route":"/technologies/ct/"},{"id":"imrt-igrt","kind":"technology","name":"IMRT / IGRT (modern external beam)","route":"/technologies/imrt-igrt/"},{"id":"mdm2-inhibitors","kind":"technology","name":"MDM2 inhibitors","route":"/technologies/mdm2-inhibitors/"}],"term":[{"id":"fnclcc-grade","kind":"term","name":"FNCLCC grade (soft-tissue sarcoma)","route":"/terms/fnclcc-grade/"}]}}