On the effect of setting of a positive surgical margin in soft tissue sarcoma

Local control is one of the primary objectives of treatment for any type of cancer, but the cost of guaranteeing this may be prohibitive and can lead to unacceptable functional outcomes for the patient. Therefore, compromises are sometimes required and may lead to an increased risk of tumor recurrence. Assessing both the risk of recurrence and how this may affect the patient is often key in decision making about how local control will be achieved. Soft tissue sarcomas can arise virtually anywhere in the body and are often large by the time of diagnosis. In the limbs, they frequently abut critical structures such as blood vessels, nerves, and bone; and the dilemma for the treating team is to determine how close is it safe to go to these structures when resecting the sarcoma. Indeed, the most frequent question asked by trainees is, “What is a safe margin when resecting a soft tissue sarcoma? ” The article by O’Donnell et al in the current issue of Cancer adds further information on this topic. One of the real problems with sarcoma surgery is the lack of clear definitions with which to classify the margin of excision. The original work by Enneking et al in the 1980s (much of it published in Cancer) led to the concept of a reactive zone around sarcomas that contained tumor cells. Resection through this layer was entitled a marginal excision, whereas surgery outside that layer was entitled wide; and, if a whole compartment was resected, then the resection was considered radical. If the tumor itself was breached at any stage, then this was considered an intralesional excision. These definitions have proved useful, but others have tried to add a numerical figure to define a safe margin. Kawaguchi et al pointed out the different values of various structures in preventing the spread of tumor cells, giving a thick barrier (like fascia) a relative score of 2 cm compared with a thin barrier (periosteum), which scored 1 cm. Those authors advised that surgery ideally should achieve a margin of 5 cm to be curative; however, even with that margin, the rate of local recurrence (LR) was 10%. Others have pointed out that adjuvant radiotherapy can dramatically narrow down the margin, and some series have suggested that a 1-mm margin is sufficient around a tumor. The current article by O’Donnell and colleagues has taken further the work by Gerrand et al, who demonstrated that a planned positive margin next to critical structures led to an acceptable rate of local control. What O’Donnell et al have now provided is confirmation of this: that the clinical setting of a positive margin affects the risk of LR. To do this, they investigated 3 groups of patients; first, a group with a critical structure-positive margin (adjacent to nerve, blood vessel, or bone), another group with a tumor bed re-excision–positive margin (after a patient has undergone a previous unplanned excision elsewhere), and a group with an unexpected positive margin during a primary resection. Then, they calculated that the 5-year LR rate was 14.6% for those with a critical structure-positive margin, 21.1% for those with a tumor bed re-excision–positive margin, and 36.6% for those with an unexpected positive margin during a primary resection. These compared with a highly commendable LR rate of just 6.5% if the margin was negative. Furthermore, the authors observed that the cause-specific survival (CSS) rate varied greatly in the 4 groups, with a 5-year CSS rate of 80.3% for those with negative margins, 59.4% for those with a critical structure-positive margin, 84.7% for those with a tumor bed re-excision–positive margin, and 59.2% for those with an unexpected positive margin during a primary resection.