News & Articles

Dr Richard Quek, Senior Consultant, Medical Oncology, shares more about soft tissue sarcomas (STS), a rare disease that affects approximately 5 per 100,000 of the population.

Soft tissue sarcomas (STS) are cancerous tumours that arise from the soft tissues of the body, such as muscle and fat cells, blood vessels and fibrous connective tissue. They are a group of rare diseases that accounts for less than 1% of all cancers diagnosed¹.

STS is a heterogeneous disease that can have several etiologies or root causes. They can be sub-divided into approximately 70 unique subtypes², each of which possesses distinct clinical presentations, genetic make-up, and different sites of tumour development and treatment strategies.

There are no clearly defined risk factors for developing the disease. However, it is known that the disease can affect individuals of different ages. Children, adolescents and young adults in particular are disproportionately affected by some common subtypes of the disease such as Ewing sarcoma and rhabdomyosarcoma.

Some rare genetic disorders that run in families may also predispose affected individuals to STS. This includes the Li Fraumeni syndrome, a hereditary genetic mutation in the TP53 tumour suppressor gene, and Familial Adenomatous Polyposis (FAP) syndrome, which is associated with the development of desmoid fibromatosis, a rare type of STS.

Types of soft tissue sarcomas

STS can be divided into two main types based on the rate of disease progression: aggressive STS and indolent STS.

Aggressive STS are fast-growing tumours. They include:

• Leiomyosarcoma, which starts in the smooth muscles found in the walls of hollow organs in the body, such as the womb, intestines, stomach, and blood vessels.
• Liposarcoma, which arises from fat cells. They can be further divided into 3 main subtypes based on their morphological appearance and genetic profiles:
  • Well-differentiated liposarcoma and dedifferentiated liposarcoma, which are characterised by the amplification of MDM2 and CDK genes. They are usually found in the abdomen.
  • Myxoid liposarcoma, which is characterised by the abnormal fusion of the CHOP-FUS genes. They often start in the arms and legs.
  • Pleomorphic liposarcoma, which is characterised by complex cytogenetics. They are typically found in the arms and legs.
• Undifferentiated pleomorphic sarcoma, which starts in the soft tissue of the legs, arms, or back of the abdomen.
• Angiosarcoma, which arises from blood vessels. They typically present on the scalp of elderly men, or in the breast, liver, spleen or heart of younger individuals.
• Synovial sarcoma, which arises in soft tissue of the limbs. They can grow to large sizes and typically affect adolescents and young adults.

Indolent STS are slow-growing tumors which are locally invasive and locally recurrent even with surgery. As they grow slowly, the risk of distant spread is low. They include:

• Desmoid fibromatosis, which arises in connective tissues of the body, typically in the arms, legs or abdomen.
• Solitary fibrous tumors can form almost anywhere in the body. They commonly occur in the lining outside of the lungs.

Other distinct subtypes of STS include Ewing sarcoma and rhabdomyosarcoma. These are usually discussed separately from the rest of aggressive and indolent STS as they tend to affect a younger population of patients and display unique clinical behaviours. Ewing sarcoma may also arise from the bone as opposed to just soft tissue alone.

Management of soft tissue sarcomas

When discussing treatment for STS, we must consider the heterogeneous nature of the disease, as each distinct subtype comes with its own unique characteristics, treatment responses, and clinical outcomes. Rather than offering a ‘one size fits all’ approach to treatment, a personalised treatment plan tailored to each individual patient and their disease can offer overall better outcomes for the patient.

Generally, localised STS is managed with surgery and radiation. In the case of localised Ewing sarcoma and rhabdomyosarcoma, which are chemosensitive tumours, chemotherapy plays a very important role in addition to surgery and radiation.

Advanced stage STS or unresectable STS are generally managed with systemic treatment, with or without radiation therapy.

While chemotherapy has been the mainstay of treatment for Ewing sarcoma, rhabdomyosarcoma, as well as advanced stage STS, the discovery of actionable mutations such as NTRK and BRAF mutations in some sarcoma subtypes have paved the way for the use of targeted therapy in the management of STS.

Multidisciplinary approach to treatment

As STS is a complex disease with many different subtypes, the management of STS involves an experienced multidisciplinary team comprising a medical oncologist, surgeon, radiation oncologist, pathologist and radiologist.

By tapping on the knowledge and expertise of doctors from different specialties, and harnessing up-to-date medical technologies, we can offer patients a holistic and comprehensive treatment plan that can achieve the best outcomes.

¹Source: “Soft tissue sarcoma in Asia”, The Chinese Clinical Oncology, Vol. 7, No. 4, 2018
²Source: World Health Organization Pathological Classification of Tumours, International Agency for Research on Cancer