(P 514) INTERSTITIAL BRACHYTHERAPY IN THE TREATMENT OF SOFT TISSUE SARCOMA: LOCAL RECURRENCE AND WOUND OUTCOMES

Objective: Interstitial brachytherapy (BT) represents one form of delivery of adjuvant radiotherapy in the treatment of soft tissue sarcoma (STS). Compared to external beam radiation (EBRT), which is the more commonly employed technique to treat STS, BT provides a dosimetric advantage by localizing to the tumor bed and minimizing damage to peripheral healthy tissue. When employing BT, wound management options include leaving the wound open with vacuum assisted closure (VAC), allowing for confirmation of surgical margins, immediately delivering radiation therapy, or closing the wound over the catheters and delaying radiation until five days following closure. Little is known about how BT, and variations in wound management/timing, affect wound and oncologic outcomes.

Methods: This retrospective institutional cohort study included all patients receiving interstitial BT following STS resection between 2015 and 2022. Patient and tumor demographics, radiation characteristics, and wound and oncologic outcomes were collected. Statistical analysis for wound complication occurrence and reoperation were assessed using chi-squared tests. The relationship between exposure variables and wound complications was analyzed using univariate logistic regression.

Results: 32 patients with STS of the extremity were treated with brachytherapy. 19 (59.4%) of the tumors were superficial. The mean tumor size was 5.8 cm (+/- 3.2 cm), and 30 (93.8%) were intermediate/high grade or ungraded sarcomas. 28 patients (87.5%) were treated with delayed wound closure at the conclusion of BT. This was potentiated by a VAC dressing while receiving BT (Table 1). 22 (68.8%) of the 32 patients included in the study were treated with definitive brachytherapy with a median time from biopsy to completion of brachytherapy (completion of treatment) of 43 days. Median implant size was 9 catheters, dose 38.5 Gray delivered in 10 fractions. 13 (40.6%) patients had wound healing complications with 7 (21.9%) requiring reoperation. Operative complications included necrosis (6), dehiscence (3), deep infection (1), cellulitis (1), and hematoma (1). Tumor size, BT catheter number, closure technique, and reconstruction technique were not associated with reoperation. 2 patients (6%) had a local recurrence, and 9 (28%) patients developed metastatic disease. There was no difference in overall survival for those who experienced complications compared with those who did not (Figure 1).

Conclusion: BT combined with surgery is an effective treatment to maximize local control for STS. Our results indicate BT has a similar wound complication and local control profile compared with reported values for patients treated with EBRT. BT offers the advantages of immediate tumor removal, condensed treatment duration, and minimized morbidity to the surrounding local tissues.