Accelerated interstitial high dose rate brachytherapy as a boost technique in the treatment of soft tissue sarcomas

Purpose/Objective: The efficacy of low dose rate (LDR) interstitial brachytherapy has clearly been established in the treatment of high grade soft tissue sarcomas. Our objective is to report the utility, technical considerations, and potential advantages of employing interstitial HDR brachytherapy as an adjuvant boost treatment for soft tissue sarcomas. Materials and Methods: Seventeen soft tissue sarcomas received HDR brachytherapy from 1990-1994. Two patients without follow-up were excluded. Sites of primary disease included the following: thigh (n=6), gluteal region (n=3), upper extremity (n=3), popliteal fossa (n=1), axilla (n=1), and chest wall (n=1). Ten of 15 lesions were grade II-III. Resection margins were negative (n=7), microscopically positive (n=7), or grossly positive (n=1). In 11 patients with previously untreated disease, postoperative HDR brachytherapy was delivered as adjuvant treatment in combination with either preoperative (n=5) or postoperative (n=6) external beam radiation therapy. Furthermore, 4 patients who had been previously irradiated and experienced recurrence underwent reresection followed by HDR brachytherapy boost; one of these patients also received additional postoperative external beam radiation therapy. In general, a delay of 2 - 3 weeks was allowed between preoperative external radiation therapy and surgery. A similar delay was employed between HDR brachytherapy and subsequent postoperative external radiation therapy. Median external beam radiation dose was 50.0 Gy, range 30.6 - 50.4 Gy. At the time of resection, blind end HDR catheters were implanted in a single plane in the tumor bed, spaced 1 cm apart, as defined by the surgical clips. The catheters were placed so as to extend 2 cm past the surgical clips in the cranio-caudad direction and 1 cm in the medial-lateral direction and stabilized with absorbable sutures. After allowing for five days of wound healing, BID brachytherapy (minimum inter-fraction interval 6 hours) was delivered on consecutive days. Median brachytherapy dose was 20 Gy (range 9.6 - 30) prescribed 1 cm from the source (median fraction 2 Gy, range 1.2 - 3). Results: Median follow-up was 26.5 months (range 2 - 63, mean 32.4). Local control was 90.9% ((10(11)) for primary cases and 75 % ((3(4))) for recurrences (crude local control 86.7 %). Both post-brachytherapy local recurrences (one margin negative, one microscopically positive) required amputation. Additional surgery for wound complications was required in (2(13)) (15.4%). A majority of preserved limbs had satisfactory functional outcome. Conclusions: Accelerated interstitial HDR brachytherapy as a postoperative boost, either alone or in combination with external beam radiation, provides a feasible alternative to a LDR approach in regards to local control, functional limb conservation, and late complications. The advantages of this strategy include increased convenience for the patient and family and elimination of radiation exposure to medical personnel. In the context of cost reduction, all or a portion of the HDR boost could potentially be offered in an outpatient setting with appropriate patient selection