A novel technique using customised templates for the application of fractionated interstitial HDR brachytherapy to the tumour bed in soft-tissue sarcomas located in the extremities

Abstract

Postoperative interstitial brachytherapy of limbs is challenging, because it is difficult to deliver a conformal dose to the tumour bed. We developed and assessed a new surgical fixation system for positioning guiding tubes in interstitial brachytherapy in order to achieve favourable geometry. A 28-year-old patient was treated with postoperative interstitial brachytherapy boost followed by external radiotherapy after the 11th recurrence of a desmoid tumour in the forearm. On the basis of preoperative imaging data, customised resorbable templates made of polydioxanone (PDS) were cut to fit in the space left by the resected tumour. These were strategically positioned in the tumour bed during surgery. In order to hold the brachytherapy-guiding tubes parallel for the duration of treatment, they were passed through a series of holes bored into the templates. Fixing the guiding tubes with PDS templates resulted in a fixed geometry, and thus in an optimal dose distribution with only little additional dose optimisation needed by the brachytherapy treatment planning system. An optimised dose to the tumour bed, and a reduction of dose to critical normal tissues, is achievable with this template system for sarcomas located between osseous structures. The PDS templates offer a more rigid fixation of the guiding tubes in relation to the surrounding anatomy even after the operation cavity has been closed. A tailored dose distribution can be achieved, thus reducing possible side-effects. Additionally, because of the self-resorbable nature of the material, a re-operation for template removal is not necessary. The potential advantages of this method are being further investigated.