Marginal miss or radioresistance? The pattern of local recurrence after operation and 3D planned radiation treatment in soft tissue sarcoma of the extremities and the limb girdles; an analysis based on image fusion

Abstract Background. Most local recurrences have developed in the clinical target volume in previously published series after combined modality treatment for soft tissue sarcoma. However, marginal misses were seen in almost 20% of the patients. The aim of the present study was to determine the location of the recurrence and the total dose at the centre point of the local recurrence for future radiation therapy planning. Material and methods. We included only patients with images in digital form, during 1999-2006 (n = 17), treated for soft tissue sarcoma with combined surgical therapy and radiotherapy at Helsinki University Central Hospital. Image fusion was used to determine the location of the recurrence in relation to radiation therapy target. Results. In the present study utilising digital image fusion, in patients with 3D CT-based radiation treatment planning the risk of marginal miss was low as only one patient of 17 relapsed outside the target. Estimated mean radiation dose at the site of local recurrence was 49.1 Gy in patients with positive margins and 48.1 Gy in patients with negative margins. Conclusion. The risk of marginal miss in soft tissue sarcoma is low after modern 3D planned radiation treatment combined with surgery. More generous use of boost might improve in-target local control.