Soft Tissue Sarcoma and its Management
Soft tissue sarcomas (STS) are tumours derived from non-epithelial extraskeletal tissues including muscle, fat and fibrous supporting structures, arising mainly from the embryonic mesoderm, with some neuroectodermal contribution [Clark 2005]. They can occur anywhere in the body but most commonly arise in the limbs (approximately 50% of cases). Other common sites include the gastrointestinal (GI) tract (25% of cases), retroperitoneum (15–20% of cases) and head and neck (approximately 9% of cases) [NCCN Clinical Practice Guidelines in Oncology 2010].
STS account for approximately 1% of all adult cancers [Jemal 2007], with an estimated incidence averaging 4/100,000/year in Europe [Casali 2009]. The incidence of STS appears to be increasing [Zahm 1997], possibly as a result of better recognition and diagnosis.
Most STS have no identifiable cause. An association between Epstein–Barr virus infections in AIDS patients and leiomyosarcoma has been observed [McClain 1995] and STS can develop 10-17 years (mean) after radiotherapy for certain tumours [Brady 1992].
The symptoms of STS are non-specific and vary according to the size and location of the tumour. Tumours usually manifest as a painless, gradually enlarging mass. Symptoms may arise due to increased pressure on adjacent organs and tissues, and the clinical picture varies according to the anatomical localisation [Clark 2005].
STS are divided into a number of subtypes according to their histology. Some of the main subtypes are summarised in table 1. The most frequently occurring STS subtypes include liposarcoma, leiomyosarcoma, synovial sarcoma and malignant fibrous histiocytoma [Clark 2005; Coindre 2001]. The different subtypes differ in their biological behaviour, their response to treatment, and their prognosis. The majority of STS subtypes, including fibrosarcoma, liposarcoma, leiomyosarcoma, pleomorphic and synovial sarcomas, show limited sensitivity to current systemic therapies and are generally incurable when diagnosed as advanced or metastatic disease [Hartmann 2005].
In contrast, other histologic types like small round cell tumours (SRCTs), including Ewing’s sarcoma, are sensitive to current chemotherapy and potentially curable. [Bertuzzi 2002; Kushner 1996].
|Site||Hiistological subtype (% of patients)|
|Muscle||Leiomyosarcoma (12%), rhabdomyosarcoma (5%), gastrointestinal stromal tumours (GIST)|
|Joints||Synovial sarcoma (10%)|
|Fibrous||Fibrosarcoma (3%), malignant fibrous histiocytoma (28%)|
|Nervous system||Including malignant schwannoma, neurofibrosarcoma, neurogenic sarcoma, primitive neuroectodermal tumours - neuroblastoma (6%), Ewing's sarcoma (2%)|
|Blood or lymph vessels||Angiosarcoma (2%), Kaposi’s hemangioendothelioma (1%)|
|Coindre 2001; Cormier 2004|