Maxfacts

Below we expand a little on what has been said on the previous page about the predominantly surgical management of soft tissue sarcoma in the maxillofacial region. In particular, we discuss briefly

• the need for radical resection of soft-tissue sarcoma;
• a general treatment scheme in adults;
• some aspects of treatment of soft-tissue sarcoma in children.

The need for radical resection of soft-tissue sarcoma

It is commonly agreed that the first line treatment with curative intent for soft tissue sarcoma is radical surgical resection, typically combined with reconstructive surgery. Reconstruction is highly relevant in this context, both with regard to functional rehabilitation and oncological outcomes. There is ample evidence that the best chances of survival strongly correlate with surgery where a sufficient negative margin is achieved; this goal, in turn, typically necessitates reconstructive surgery. The dimension of a sufficient negative margin is usually quoted as 1 to 2 cm in all directions (although this is a matter of debate). This is a blunt, generalised statement which does not take into account that body tissues as well as malignant growths are not uniform and directionless (isotropic) entities. Furthermore, such a margin can be challenging to achieve in the head & neck region because of the vicinity and density of vital structures.

A more nuanced and rational consideration of the requirements for radical surgical resection needs to include the typical local growth behaviour of soft tissue sarcomas and the respective local anatomy. Similar nuanced considerations apply to the regional and distant spread (metastasis) of soft tissue sarcomas, which occurs predominantly via the haematogenous mechanism, whilst more common head and neck malignancies (carcinomas) tend to spread via lymphatic and haematogenous routes.

Local spread of soft tissue sarcoma is characterised by initial expansive growth. This is less limited by the need of the tumour to transgress any tissue borders but more limited by the building-up of a local capsule comprising a mixture of tumour tissue, inflammatory local tissue and normal tissue cells. Within this growth pattern, the tumour will grow along a path of least resistance, following local anatomical directions defined by fascial planes, muscle or nerve fibres, or blood vessel architecture. A growth path of least resistance means that local tumour growth does not occur with equal probability in all directions, but rather in preferred main direction(s) defined by local tissue anatomy, in an orderly process that will not transgress tissue borders but will displace these (similarly, the regional spread of head & neck carcinomas via regional neck lymph nodes is not a random process, but also follows an anatomically defined pattern). Eventually, at a later stage, the growth will transgress tissue borders and change to invasive local tumour growth.

The growth patterns as characterised by various imaging modalities (MRI, ultrasound, CT), together with the histopathology evaluation of biopsy samples to assess the grade and type of the tumour tissue, inform the surgical planning for resection and reconstruction. There are different ways in which a radical resection can be carried out. A rational way is to think about ‘compartments’, functional units, and remove the unit. An example would be half of the tongue as a functional anatomical unit (or subunit), given that there will be a higher probability for tumour growth along the tongue muscle rather than perpendicular to it. Such compartmental resection may sound counterproductive as it may create a larger defect than other surgical approaches. However, compartmental resection can reduce the rate of local tumour recurrence by removing a larger volume of potentially relapse-prone local tissue. In addition, functional rehabilitation by reconstruction with free flaps may be more successful in this anatomy-minded approach (the anterolateral thigh flap is commonly used).

A general treatment scheme in adults

Given that soft tissue sarcomas of the head and neck are rare malignancies, yet display many subtypes and variations of response to treatment(s), only some very general treatment protocols can be outlined. Treatment may start with two cycles of chemotherapy (with different agents preferred in Europe and North America), followed by radical resection with margins appropriate for the original tumour size even if chemotherapy causes shrinkage of the tumour. If pathology after surgery demonstrates tumour necrosis, chemotherapy may be continued postoperatively. The rationale of assessing chemotherapy effect is fairly sound but, of course, it does not help with preservation of vital structures (for example, eye) as the surgical margins are based on original tumour dimensions. Response to chemotherapy varies; it seems to improve local disease control but does not improve overall survival as it does not prevent the occurrence of distant metastases.

As a general trend, low grade tumours are usually treated surgically, high grade tumours are more likely to be treated by surgery and postoperative radiotherapy. Where possible, local disease control by surgery is significantly better than by radiotherapy. Apart from more surgery, radiotherapy is an option postoperatively when surgical margins were insufficient, although evidence suggesting this improves survival is lacking.

Some aspects of treatment in children

The treatment of soft tissue sarcoma (rhabdomyosarcoma being the most common paediatric form) in children differs somewhat from the treatment in adults. In children, in addition to radical surgery, chemo- and radiotherapy have a more prominent role than in the treatment of adults. There appear to be survival benefits in children form this multi-modality approach. In particular, chemotherapy prior to surgical resection seems advantageous. However, chemo- and radiotherapy in children, especially in the age group up to 5 years, carries a substantial burden of long-term adverse effects. These include the development of significant craniofacial, endocrine and dental changes (abnormal growth and dysfunction) and an increased risk of secondary malignancies later in life.

Local recurrence is the main cause of treatment failure, so a careful balance between sufficiently radical treatment to control local disease (including acute and chronic adverse effects) and preservation of the best possible quality of life is a crucial consideration. In this regard, replacing conventional radiotherapy by proton irradiation may prove helpful in local disease control with fewer adverse effects than conventional photon-based radiotherapy. Proton irradiation causes less damage to adjacent healthy tissues beyond its target region (in contrast to high energy photons which expose also tissue beyond their target area to high radiation exit doses). Early trials of immunotherapies were disappointing.