Sarcomas are the group of malignancies that develop from muscle, adipose, bone, cartilage or fibrous tissue. In adults they are a very uncommon type of cancer with many different sub-groups. In the palliative care context patients often develop bulky pelvic metastases with compression effects or multiple lung metastases with dyspnoea. These patients are often young adults which can make this especially challenging.
Sub-types and Grading
Sarcomas are classified based on the apparent type of tissue. Some of the more common types include gastro-intestal stromal tumours, liposarcomas, leiomyosarcomas, synovial sarcomas, malignant peripheral nerve sheath tumours, desmoplastic small round tumours, angiosarcomas, Ewing's tumours and undifferentiated soft tissue sarcomas.
Most sarcomas tend to be graded from I (well differentiated) to III (poorly differentiated) based on differentiation, necrosis and mitotic activity.
Sarcomas are rare. There are about 10,000 new diagnoses of sarcomas each year in the United States and about 5,000 deaths due to sarcomas.
Some of the known risk factors include various genetic conditions (e.g. neurofibromatosis), previous exposure to radiation, and previous chemotherapy.
Sarcomas most commonly present with a painless mass that develops over a number of weeks or months. The following table gives an indication of the most to least common site of sarcomas:
|Groin or upper leg||50%|
|Chest, abdomen or retroperitoneal space||30%|
|Head or neck||10%|
The rate of growth varies but poorly differentiated tumours tend to grow faster. As the tumour deposit enlarges it tends to cause discomfort and pain and compresses other structures such as the venous system causing leg oedema.
Spread is most commonly haematogenous with lung metastases most frequent. At diagnosis about 10% of patients have distant metastases and of these patients 85% of them have lung metastases; these patients are primarily those with grade II or III tumours. The presence of distant metastases obviously is associated with a a poor prognosis
Lymphatics spread is uncommon and the presence of nodal metastases is associated with a poor prognosis.
In patients who have curative treatment for a local lesion, about 25% will develop recurrent disease. Recurrent disease is more common for patients with large tumours greater than 5cm in diameter and with a higher grade.
Investigations and Diagnosis
Differentials of a localized soft-tissue mass include:
- Benign soft tissue tumours (lipomas) - these are very common
- Other malignancies (e.g. melanoma)
Benign soft tissue tumours such as lipomas are very common and therefore it is not always necessary to investigate a patients with a soft-tissue lump. The exception to this are When a patient has a lump that is obviously increasing in size or one that is painful or one that is very large.
Patients with a potential sarcoma should be referred to a specialist centre for work-up.
A plain radiograph is helpful to look at the bone and for extra-bony calcification (which might occur in an osteosarcoma)
MRI is the investigation of choice for suspected sarcomas and much better differentiates between neoplasm and surrounding muscle and other soft tissue than CT scan.
Diagnosis is ultimately made by biopsy, which should be performed after initial imaging work-up. A core biopsy is the preferred biopsy type and is accurate in distinguishing between malignant and benign soft tissue tumours. For deep lesions, CT or ultrasound guidance is needed.
Chest CT scan is a good investigation to look for pulmonary metastases.
Staging and Prognosis at Diagnosis
Sarcomas are staged I to IV using a TNM system in conjunction with the grade
- T1 - < 5cm versus T2 > 5cm
- NO - no nodes involved; N1 - regional nodes involved
- M0 - no distant metastases; M1 - distant metastases
Staging is subdivided further with Ia and Ib and IIa and IIb as follows:
- Stage Ia - T1 N0 M0 G1
- Stage Ib - T2 N0 M0 G1
- Stage IIa - T1 N0 M0 G2/G3
- Stage IIb - T2 N0 M0 G2
- Stage III - T2 G 3 OR Any T and G with N1 M0
- Stage IV - Any T, any N, any G with M1
Overall survival at 5 years is 90% for stage I disease at diagnosis, 80% for stage II disease and 55% for stage III disease. Where there are distant metastases, prognosis is much worse with a median survival of 1 year and only 20% of patients alive at 3 years. In patients with a solitary pulmonary metastasis that can be resected 5-year survival however is close to 40%.
For local disease treatment primarily involves wide surgical resection. Adjuvant radiotherapy reduces the risk of recurrent disease.
Different tumour types respond quite differently to chemotherapy. Some tumours are relatively chemoresistance and chemotherapy regimes given are often quite aggressive and intense; doxorubicin and ifosfamide are commonly used agents. Doxorubicin is particularly associated with cardiotoxicity in addition to the usual reversible cytotoxic complications. Ifosfamide can cause haemorrhagic cystitis and CNS toxicity. Most other conventional cytotoxics are rarely beneficial. The newer antibody agents are showing promise for certain sarcoma sub-types with particular receptors.
Supportive and Palliative Treatment
Patients with sarcomas are often young adults. Bulky metastatic intra-abdominal disease can cause obstructive problems such as severe peripheral oedema from inferior vena caval pressure and acute renal failure from ureteric obstruction. Bulky pulmonary metastases cause a progressive dyspnoea that is often is very distressing and often only responds to benzodiazepines.