# Retroperitoneal sarcoma

Source: https://onco.cc/cancers/retroperitoneal-sarcoma/  
OnCo record `retroperitoneal-sarcoma` (Cancer). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

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.

Complete 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.

Systemic 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.

## Fields

- Kind: Cancer
- Last checked: 2026-09-17
- Also known as: Retroperitoneal soft tissue sarcoma; RPS; Abdominal sarcoma
- Tags: subtype-page
- 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

## Sections of this record

The page is a hub with ten sections in reading order; large sections have their own page. The same plan as JSON: https://onco.cc/api/v1/cancers/retroperitoneal-sarcoma/sections.json

- Overview (on the hub): The TL;DR, the family this cancer belongs to, the organ, who gets it and what the state of the art is. https://onco.cc/cancers/retroperitoneal-sarcoma/#overview [3 state-of-the-art points]
- Types and stages (on the hub): Anatomy, the subtypes and how they differ, how it is staged, and where advanced disease spreads. https://onco.cc/cancers/retroperitoneal-sarcoma/#what-it-is [5 subtypes]
- Symptoms and diagnosis (on the hub): How this cancer shows itself, how the diagnosis is confirmed, and the biomarkers clinicians test for. https://onco.cc/cancers/retroperitoneal-sarcoma/#finding-it [4 biomarkers]
- Treatment (on the hub): The standard of care by setting, the medicines, surgery and radiotherapy named in it, and the regimens behind them. https://onco.cc/cancers/retroperitoneal-sarcoma/#treating-it [3 settings, 3 decisions with options]
- Trials and papers (on the hub): Trials recruiting now, the landmark trials, the trials held by this cancer's subtypes, the key papers and what they mean, the latest literature, and the milestones year by year. https://onco.cc/cancers/retroperitoneal-sarcoma/#evidence [2 trials, 5 key papers, 4 milestones]
- Biology and targets (on the hub): The molecular landscape: the targets and how often each appears, the pathways, the mechanics stages and the preclinical models. https://onco.cc/cancers/retroperitoneal-sarcoma/#science [2 targets]
- Countries and centres (own page): Cases by country, the UK and NHS pathway and other country lenses, the expert centres with trials on record, and the centres named on this cancer's subtypes. https://onco.cc/cancers/retroperitoneal-sarcoma/where-you-are/
- Decisions and support (on the hub): The decisions you may face, the aids that walk through them, the warnings on record, the first sixty days and the questions to ask. https://onco.cc/cancers/retroperitoneal-sarcoma/#living-with-it [16 questions, 6 red cards]
- Pipeline and open problems (own page): Everything in development, the medicines held by this cancer's subtypes, the open problems and what is being done about them, the roadmaps, and what changed on this record. https://onco.cc/cancers/retroperitoneal-sarcoma/coming/ [6 medicines, 2 trials, 3 open problems]
- Data (own page): Every connected record, the notes, the JSON, Markdown and RDF twins, and where the record came from and when it was checked. https://onco.cc/cancers/retroperitoneal-sarcoma/data/ [29 connected records]

## Standard of care

- Primary, resectable: 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. ([STRASS (EORTC 62092)](https://onco.cc/trials/strass/), [IMRT / IGRT (modern external beam)](https://onco.cc/technologies/imrt-igrt/), [CT (computed tomography)](https://onco.cc/technologies/ct/), [FNCLCC grade (soft-tissue sarcoma)](https://onco.cc/terms/fnclcc-grade/))
- High-risk dedifferentiated liposarcoma or leiomyosarcoma: Neoadjuvant chemotherapy within STRASS2 (doxorubicin-ifosfamide or doxorubicin-dacarbazine) or up-front surgery; no proven adjuvant therapy. ([Doxorubicin](https://onco.cc/drugs/doxorubicin/), [Ifosfamide](https://onco.cc/drugs/ifosfamide/), [Dacarbazine](https://onco.cc/drugs/dacarbazine/))
- Recurrent or metastatic: 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. ([Trabectedin](https://onco.cc/drugs/trabectedin/), [LMS-04](https://onco.cc/trials/lms-04/), [Eribulin](https://onco.cc/drugs/eribulin/), [MDM2 inhibitors](https://onco.cc/technologies/mdm2-inhibitors/), [Pazopanib](https://onco.cc/drugs/pazopanib/))

## State of the art

- 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.

## Open problems

- 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.

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Sarcoma
- TARPSWG: https://www.tarpswg.org

## Connected records

- cancers: [Leiomyosarcoma](https://onco.cc/cancers/leiomyosarcoma/), [Liposarcoma](https://onco.cc/cancers/liposarcoma/), [Perivascular epithelioid cell tumour (PEComa)](https://onco.cc/cancers/pecoma/), [Sarcomas (soft tissue, bone, GIST)](https://onco.cc/cancers/sarcoma/), [Soft tissue sarcoma of the extremity (localised and advanced)](https://onco.cc/cancers/extremity-soft-tissue-sarcoma/), [Undifferentiated pleomorphic sarcoma (UPS)](https://onco.cc/cancers/undifferentiated-pleomorphic-sarcoma/), [Uterine sarcoma](https://onco.cc/cancers/uterine-sarcoma/)
- key papers: [LMS-04: doxorubicin plus trabectedin followed by trabectedin maintenance versus doxorubicin alone in metastatic leiomyosarcoma](https://onco.cc/key-papers/paper-lms-04-doxorubicin-trabectedin-lancet-oncol-2022/), [Primary retroperitoneal sarcomas: a multivariate analysis of surgical factors associated with local control](https://onco.cc/key-papers/paper-bonvalot-retroperitoneal-sarcoma-compartmental-jco-2009/), [Soft tissue and visceral sarcomas: ESMO-EURACAN-GENTURIS clinical practice guideline](https://onco.cc/key-papers/paper-esmo-sts-guideline-gronchi-ann-oncol-2021/), [STRASS (EORTC 62092): preoperative radiotherapy plus surgery versus surgery alone for primary retroperitoneal sarcoma](https://onco.cc/key-papers/paper-strass-lancet-oncol-2020/), [Variability in patterns of recurrence after resection of primary retroperitoneal sarcoma (TARPSWG)](https://onco.cc/key-papers/paper-tarpswg-retroperitoneal-sarcoma-gronchi-ann-surg-2016/)
- drugs: [Dacarbazine](https://onco.cc/drugs/dacarbazine/), [Doxorubicin](https://onco.cc/drugs/doxorubicin/), [Eribulin](https://onco.cc/drugs/eribulin/), [Ifosfamide](https://onco.cc/drugs/ifosfamide/), [Pazopanib](https://onco.cc/drugs/pazopanib/), [Trabectedin](https://onco.cc/drugs/trabectedin/)
- trials: [LMS-04](https://onco.cc/trials/lms-04/), [STRASS (EORTC 62092)](https://onco.cc/trials/strass/)
- technologies: [CT (computed tomography)](https://onco.cc/technologies/ct/), [IMRT / IGRT (modern external beam)](https://onco.cc/technologies/imrt-igrt/), [MDM2 inhibitors](https://onco.cc/technologies/mdm2-inhibitors/)
- terms: [FNCLCC grade (soft-tissue sarcoma)](https://onco.cc/terms/fnclcc-grade/)
- people: [Patricia Pautier](https://onco.cc/people/patricia-pautier/), [Sylvie Bonvalot](https://onco.cc/people/sylvie-bonvalot/)
- companies: [French Sarcoma Group](https://onco.cc/companies/french-sarcoma-group/)

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JSON: https://onco.cc/api/v1/entities/retroperitoneal-sarcoma.json