(P 202) LONG-TERM EXPERIENCE WITH INTRAOPERATIVE ELECTRON RADIATION THERAPY BOOST IN EXTREMITY SARCOMA

Objective: In patients with extremity soft tissue sarcoma (eSTS), we describe outcomes of preoperative external beam radiation therapy (EBRT), limb sparing surgery (LSS), and IOERT.

Methods: One hundred and eighteen patients with eSTS treated between October 17th, 2002 and July 28th, 2021 were identified. EBRT was delivered preoperatively followed by LSS and IOERT.

Results: The median follow-up was 24.9 months. The presentation was primary in 102 (94%) patients and recurrent in 6 (6%) patients. Tumor location was lower extremity in 82 (76%) patients and upper extremity in 26 (24%) patients. Stage distribution was as follows: 3 (3%) IA, 24 (22%) IB, 31 (29%) II, 24 (22%) IIIA, and 25 (23%) IIIB. Final surgical margins were negative in 96 (89%) patients. The 5-year local control, failure free survival and overall survival were 94%, 75%, and 64%, respectively. Univariate analysis identified age >50, lower extremity, and higher grade as significant negative prognostic factors for OS. Grade 3 fracture or osteoradionecrosis requiring surgical fixation, neuropathy, and lymphedema occurred in 7 (6%), 1 (1%), and 0 patients, respectively.

Conclusion: This study represents one of the largest series using preoperative EBRT, LSS, and IOERT for eSTS, with high local control and low rate of late severe toxicity.