Soft Tissue Sarcoma

Soft tissue sarcomas are a heterogeneous group of malignant mesenchymal tumours arising from:

• Muscle
• Fat
• Fibrous tissue
• Blood vessels
• Peripheral nerves
• Other connective tissues

There are many histological subtypes and they do not all respond to the same systemic therapy.

Important examples include:

• Undifferentiated pleomorphic sarcoma
• Liposarcoma
• Leiomyosarcoma
• Synovial sarcoma
• Myxofibrosarcoma
• Malignant peripheral nerve sheath tumour
• Angiosarcoma
• Epithelioid sarcoma

The strongest broad prognostic factors are:

• Histological grade
• Tumour size
• Depth
• Metastatic disease
• Surgical margin

Most extremity sarcomas spread haematogenously, particularly to the lungs. Routine lymphadenectomy is unnecessary because nodal spread is uncommon except in selected histologies.

Typical presentation is a painless enlarging soft tissue mass.

A soft tissue mass requires urgent sarcoma assessment when it is:

• Increasing in size
• Deep to fascia
• Approximately 5 cm or larger
• Painful without another explanation
• Recurrent after previous excision

Small superficial sarcomas do occur, so size alone cannot exclude malignancy.

Do not assume that a painless mass is benign.

A common serious error is unplanned excision of a presumed lipoma before imaging or biopsy.

MRI with contrast: investigation of choice for extremity and trunk lesions.

Define:

• Size
• Fascial compartment
• Neurovascular relationship
• Bone involvement
• Internal necrosis

CT chest: standard metastatic staging for most intermediate and high grade extremity sarcomas because lung metastases predominate.

Biopsy

Image first, then biopsy.

Use image guided core needle biopsy in most cases.

The tract should:

• Follow a direct longitudinal path
• Avoid uninvolved compartments
• Avoid neurovascular bundles
• Avoid creating a transverse scar
• Be placed so it can be removed with the tumour specimen

Do not shell out or excise an undiagnosed deep mass before pathology is established.

Patients treated at specialist sarcoma centres have better local control than patients managed through unplanned procedures.

Localised extremity sarcoma

The cornerstone is wide surgical resection with negative margins.

The objective is removal of tumour with an intact surrounding cuff of uninvolved tissue or an anatomical barrier.

A microscopically negative margin does not require sacrificing a major nerve or vessel merely to achieve an arbitrary centimetre distance when an intact fascial barrier provides an oncologically appropriate margin.

Remove the biopsy tract with the specimen.

Limb salvage

Most extremity soft tissue sarcomas can now be treated with limb preserving surgery.

Amputation is reserved for selected cases where:

• Adequate margins cannot otherwise be achieved
• Major neurovascular involvement prevents a functional reconstruction
• Severe infection or tissue destruction eliminates meaningful salvage

Radiotherapy

Radiotherapy substantially improves local control for many intermediate and high grade sarcomas but has not clearly improved overall survival across all disease.

Use particularly for:

• Deep tumours
• Large tumours
• High grade disease
• Close anatomical margins
• Sites where local recurrence would be difficult to salvage

Preoperative radiotherapy commonly uses approximately:

50 Gy in 25 fractions

Advantages:

• Smaller treatment field
• Lower long term fibrosis burden

Disadvantage:

• Higher acute wound complication risk

Postoperative radiotherapy commonly requires approximately:

60 to 66 Gy

depending on margins and local anatomy.

Advantages:

• Final pathology is known before radiation

Disadvantages:

• Larger treatment field
• Greater late fibrosis and stiffness

Small low grade tumours

A small superficial or selected low grade tumour that is completely excised with a satisfactory margin may not require radiotherapy.

Systemic chemotherapy

Routine chemotherapy is not required for every resected adult soft tissue sarcoma.

Consider perioperative chemotherapy in selected high risk disease according to:

• Histology
• Size
• Grade
• Site
• Patient fitness

Advanced disease

A standard reference first line treatment for many metastatic adult soft tissue sarcomas is:

Doxorubicin 75 mg/m² IV every 3 weeks

for a limited cumulative course according to cardiac tolerance.

Doxorubicin remains the reference systemic agent for many advanced subtypes.

Doxorubicin plus ifosfamide provides a higher response rate and longer progression free survival but substantially greater toxicity, without a consistent overall survival advantage. It is most useful when rapid tumour shrinkage is particularly important.

Treatment after progression is histology specific and may include:

• Pazopanib
• Trabectedin
• Eribulin
• Gemcitabine based treatment
• Ifosfamide
• Dacarbazine

depending on subtype.

Pulmonary metastases

Pulmonary metastasectomy can provide long term disease control in carefully selected patients with:

• Controlled primary tumour
• Limited pulmonary disease
• Long disease free interval
• Ability to remove all metastatic deposits

Nodal disease

Routine sentinel node or lymph node dissection is unnecessary for most sarcomas.

Greater nodal propensity occurs in selected histologies including:

• Epithelioid sarcoma
• Clear cell sarcoma
• Angiosarcoma
• Some synovial sarcomas

Clinically involved nodes should be investigated and managed according to histology.

Unplanned excision

A patient referred after inadvertent excision of a sarcoma should undergo:

• MRI of the operative field
• Chest staging
• Pathology review
• Wide reexcision of the contaminated tumour bed when feasible

Residual microscopic disease is common even when the original wound appears normal.