Abdominal metastases of primary extremity soft tissue sarcoma: A systematic review

BACKGROUND: Despite the fact that about one third of patients with primary localized extremity soft tissue sarcoma (eSTS) will develop metastatic disease, abdominal metastases (AM) and retroperitoneal metastases (RM) constitute rare events. There is no clear consensus on how to achieve follow-up on patients with primary localized eSTS following curative resection, especially regarding the surveillance of potential AM/RM. AIM: To systematically analyse incidence, diagnosis, treatment and outcome of AM/RM in eSTS patients. METHODS: In this systematic review, 899 studies available in PubMed and published between 2000 and 2018 were screened, identifying 17 original articles focused on AM or RM in eSTS. Article selection was based on the PRISMA guidelines, using the search terms (abdominal metastasis AND soft tissue sarcoma) and (soft tissue sarcoma metastasis abdomen). All studies published between January 1, 2000 and December 31, 2018 were screened. Further articles were identified by cross-searching article references, with the final search date being February 18, 2019. Due to limited data and the different reporting techniques used, the present review focused on descriptive analysis of the included studies. RESULTS: Of the 17 studies included, six original articles reported on incidence ± diagnosis, therapy and outcome in AM and RM, whilst three original and eight case reports focused on diagnostic pathway, therapeutic procedures or outcomes without allowing conclusions regarding incidence of AM and RM. According to the former six studies, incidence of AM ranged from 0.9%-5.6% in patients with miscellaneous histological subtypes, and up to 12.1% in patients with myxoid liposarcoma. The most common histological subtypes that developed AM or RM were (myxoid) liposarcoma and leiomyosarcoma, but also rare subtypes such as epithelioid sarcoma, myxofibrosarcoma, synovial sarcoma, and malignant peripheral nerve sheath tumour had been reported to develop AM/RM. Surgery for AM/RM was performed in five of eight case-reports (62.5%) and in 20.8%-100.0% of original articles. In particular, patients with hepatic metastases undergoing metastasectomy had a survival benefit compared to patients treated with chemotherapy or best supportive care (> 3 years vs < 6 mo). CONCLUSION: Patients with eSTS should undergo surveillance with abdominal ultrasonography/computed tomography, or even whole-body-magnetic resonance imaging to detect AM/RM at an early stage.