Rhabdomyosarcoma

Sarcomas

Sarcomas are rare types of cancer that develop in the supporting tissues of the body, such as bone, muscle or cartilage.

There are two main types of sarcoma:

• Soft tissue sarcomas can develop in muscle, fat, blood vessels, or in any of the other tissues that support, surround and protect the organs of the body. More than half of all soft tissue sarcomas diagnosed in childhood are rhabdomyosarcoma. Other types of soft tissue sarcoma include fibrosarcoma, malignant peripheral nerve sheath tumours, peripheral primitive neuroectodermal tumours (pPNETs), Kaposi sarcoma and Ewing and Askin tumours of soft tissue.
• Bone sarcomas can develop in any of the bones of the skeleton. The two most common types of bone sarcoma in children are osteosarcoma and Ewing sarcoma.

Rhabdomyosarcoma (RMS)

RMS is the most common type of soft tissue sarcoma to occur in childhood.

It arises in muscle or fibrous tissue and can occur in almost any part of the body. The most common sites are around the head and neck, the bladder or the testes. Sometimes tumours may be found in a muscle or a limb, in the chest, or in the abdominal wall.

Occasionally, if the tumour is in the head or neck region, it can spread into the brain or the fluid around the spinal cord.

Nearly two thirds of RMS are of the embryonal sub-type (arising in primitive muscle cells). The other third are of the more aggressive alveolar sub-type.

The causes of RMS are unknown although children with certain rare genetic disorders, such as Li Fraumeni syndrome, have a higher risk of developing RMS.

Incidence

RMS is the most common type of soft tissue sarcoma to occur in childhood, accounting for 53 per cent of cases (and four per cent of all childhood cancers). There are up to 60 new cases a year in the UK.

Incidence is greatest in children under the age of 10 years. The age distribution is different for boys and girls. In boys incidence peaks at age 3 to 4 years. In girls, it peaks earlier at 1 to 2 years and then declines. It is more common in boys.

Rhabdomyosarcoma Survival Rate

The five year survival rate for childhood RMS is 71 per cent.

Age is an important prognostic factor. Children diagnosed at the age of 10 to14 years have lower survival, around 50 per cent, than children diagnosed at a younger age.

The overall survival rate for other types of soft tissue sarcoma is the same as RMS, at 71 per cent, but the age pattern is different – with diagnosis during infancy being associated with a low survival rate.

Other important prognostic factors are the site, size, type of RMS, whether it has spread, associated genetic changes, whether complete removal is possible and general health of the child.

Symptoms of soft tissue sarcomas depend on the part of the body affected. 

The most common sign is a swelling or lump.

• If the tumour is in the head area, it can sometimes cause a blockage and a discharge from the nose. Occasionally an eye may appear swollen and protruding.
• If the tumour is in the abdomen, the child may have discomfort in the abdomen and difficulty going to the toilet.
• If the tumour is in the bladder, the child may also have blood in the urine.

A variety of tests and investigations may be carried out to diagnose a soft tissue sarcoma. Blood and bone marrow tests will be taken. A biopsy is usually taken so the tumour cells can be examined under the microscope. Imaging techniques – including X-ray and ultrasound, CT or MRI scans – will be used to determine the exact size and location of the tumour and whether it has spread to other parts of the body. Then the cancer can be staged, guiding treatment.

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Before treatment commences, doctors will stage the tumour. This is a complex classification based on the site of the original tumour, its size, whether lymph nodes are involved, whether spread has occurred and the histology. This then guides decisions about treatment. A combination of chemotherapy, radiotherapy and surgery is likely to be used. 

Sometimes it will not be possible to remove the tumour by surgery either because it is too large, inaccessible or because it has spread to other parts of the body. In these cases, treatment is likely to involve a combination of chemotherapy and radiotherapy.

High dose chemotherapy may be required, predominantly in patients with relapsed disease, necessitating stem cell rescue to restore damaged bone marrow.

The benefit of chemotherapy is firmly established for RMS but not for other types of soft tissue sarcoma; surgery is considered the mainstay of treatment for children with these tumours.

 Side effects and complications of treatment

Treatment often causes side effects and these will be discussed before treatment starts.

The possible side effects depend on the treatment given and the part of the body being treated but may include nausea and vomiting, hair loss, reduced resistance to infection, bruising and bleeding, tiredness and diarrhoea.

These problems are all temporary and can be minimised with good supportive care.

Follow-up

Children will have regular follow-ups to check for any recurrence of the cancer and for any problems which may arise as a result of the treatment they were given.

A small number of children may develop long-term problems because of their cancer treatment.

Surgery and radiotherapy may both cause functional or cosmetic problems depending on the area of the body in which the tumour occurred. Chemotherapy may cause problems with heart and kidney function, fertility problems and a small increase in risk of developing another cancer.

Occasionally, the cancer can recur. This is called a relapse. Relapse occurs most likely as a result of a few of the original cancer cells surviving the treatment. Sometimes, this is because cancer cells spread to other parts of the body and were too small to be detected during the follow-up immediately after treatment.

The treatment and prognosis for relapsed RMS will depend on the site of relapse, whether there was previous radiotherapy, the original size at diagnosis, and the time to relapse.

Many children have their treatment as part of a clinical trial. 

Trials aim to improve understanding of the best way to treat the cancer, usually by comparing the standard treatment with a new or modified version.

If appropriate, the child’s medical team will discuss participation in a relevant trial. Participation is optional but may offer the opportunity to receive new treatments.

Children with Cancer UK is funding a number of research projects focused on rhabdomyosarcoma.

Further information