(P 289) SIX YEAR FOLLOW-UP ON CIVASHEET® USE FOR SOFT TISSUE SARCOMA: A SINGLE INSTITUTION EXPERIENCE

Objective: CivaSheet® is a palladium-103, implantable, intraoperative radiation therapy device which emits unidirectional radiation that enables boost doses in patients who have otherwise received the maximum radiation dose. Here, we present six year follow-up experience with this technology.

Methods: A retrospective chart review of all patients with STS treated with surgical resection and CivaSheet® placement at a tertiary care center from January 2018 to June 2025 was performed. Adjuvant radiation was administered by a palladium-103 implant, which delivered an average of 47 Gy (35-55) to a depth of 5 mm.

Results: Nine patients underwent CivaSheet® placement from January 2018 until December 2019 for a total of 10 CivaSheets® placed and followed for a mean of 45 months (4-76 months). 5 patients were alive at present analysis for an overall survival rate of 50%. Four tumors were located in the retroperitoneum, two in the chest, two in the groin, and two within the lower extremity. At the time of tumor resection and CivaSheet® placement, tumor sizes ranged from 2.5 cm to 13.8 cm with an average of 7.6 cm. Seven patients’ tumors recurred locally for a local recurrence rate of 70%. Three patients had modified accordion grade 4 complications necessitating additional surgery for CivaSheet® removal. Extremity tumors unanimously developed modified accordion grade 4 adverse events.

Conclusion: On follow-up, CivaSheet® continues to be an acceptable alternative treatment modality for recurrent, non-extremity tumors.