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SURGICAL MARGINS FOR SOFT TISSUE SARCOMA: SIZE DOES MATTER

Soft tissue sarcomas are uncommon. With an incidence of 1–2 per 100 000 head of population, soft tissue sarcomas account for only 1 in every 1000 cancers. As such, it is not surprising that the exposure of most surgeons to this class of tumour will be limited. Experience at recognized tumour centres over the last two decades has established clear guidelines for treatment of soft tissue sarcomas. The combination of appropriate surgery with radiotherapy provides good local control with local recurrence of 10% or less. For those specialized in the field of sarcoma surgery, debate continues over the definitions, and hence use, of specified surgical margins. Although the definitions of intralesional, marginal and radical margins are clear, the nature of wide margins remains controversial. This controversy is important because guidelines would suggest that the best margin to combine with radiotherapy to enhance limb-sparing surgery is the wide margin. Traditionally, a wide margin has been described as a margin that is at least 5 cm wide and/or which includes a cuff of normal tissue. However, such a definition fails if one deals with a sarcoma in a location that does not have 5 cm of tissue to spare, such as a finger or toe. Furthermore, there are areas where resection with wide margins would necessitate the removal of adjacent vital neurovascular structures, such as with tumours that arise in the flexor fossae (politeal fossa, inguinal region and axilla). Here, no compartments exist to contain the tumour and permit, by definition, wide margin surgery. Dickinson et al., in their review of 324 patients treated at a single institution, have introduced a more recent concept that may modify the traditional wide margin; that is, the quality of the surgical margin. They explore the absolute thickness of the margin, ranging from <1mm to >20mm, and also the relationship of contamination to the rate of local control. What they have found is that local control of disease is related to the quality of the margin, that wider margins are associated with better disease control and, importantly, that any contamination despite the absolute thickness of the margin is correlated to poor local disease control. Their results are important because even today, soft tissue sarcomas continue to be intentionally treated by those not expert in the field or those who have stumbled on a soft tissue sarcoma (oops, lesions) believing them to be innocent lipomas. In these situations, the margins are characteristically narrow and positive margins are commonly found. Such margins are prone to contamination and the outcomes for these patients are without doubt compromised. Dickinson et al. have shown that in a tumour centre where carefully planned surgery may allow close margins, better results can follow. Notwithstanding this, contamination still occurs with inferior results as reported by Dickinson et al. Despite the subcategorization by Dickinson et al. of their use of wide margins, the discipline of sarcoma surgery still would argue that the nature of the specific margin rather than the absolute thickness should also be considered. For example, it is agreed that the quality of the fascia lata, although only several millimetres thick is superior to an equivalent thickness of muscle if the muscle is all that surrounds the tumour. In this regard, the report by Dickinson et al. has not enunciated the conditions to which their definition of wide margins has been applied. It is incumbent on the reader to be mindful that this is an important point and that relying on a margin greater than 1mm alone may not be safe in all situations. Further, Dickinson et al. have reported that patients whose tumours were resected with radical margins had a poorer prognosis. Their result would seem paradoxical; however, in the modern era, radical margins are usually reserved for exceptionally large or contaminated tumours, which would be associated with a much poorer prognosis because large size is an independent prognostic factor for poor outcome. The study by Dickinson et al. emphasize the need to standardize the definitions of surgical margins so that appropriate comparisons may be undertaken across tumour centres to identify the best margins that not only control local disease, but also enhance the potential for limb-sparing surgery. Until then, a practical definition of wide margin may be that a tumour is excised with at least 2 cm of normal tissue in the longitudinal direction and that the tumour be contained by at least one normal anatomic layer (muscle or named fascia) in the radial direction. Important lessons gleaned over time include: (i) any tumour greater than 5 cm or deep to the deep fascia should be regarded as a sarcoma until proven otherwise; (ii) the diagnosis of a ‘chronic haematoma’ should always be held with great suspicion, and (iii) sarcomas are best treated at a tumour centre with units that specialize in the multidisciplinary management of this rare tumour.