Experience with Intraoperative Radiation Therapy in an Urban Cancer Center

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Abstract
Background/Objective: Intra-operative radiation therapy (IORT) is a newer partial breast irradiation technique that has been well studied in 2 large, randomized trials, the TARGIT-A and ELIOT trials. We initiated our IORT program in 2018 in the context of a registry trial and aim to report our early results thus far. Methods: We instituted an IORT practice using Intrabeam® low energy 50kVp x-rays for selected breast cancer cases in 2018. Patients were enrolled on our institutional registry protocol which allowed for IORT in ER+ patients with grade 1-2 DCIS ≤ 2.5cm or invasive disease ≤ 3.5cm in patients of at least 45 years of age. Results: Between January 2018 and December 2021, 181 patients with clinical stage 0-IIA ER+ breast cancer were evaluated. One hundred sixty-seven patients ultimately received IORT to 172 sites. The majority of patients received IORT at the time of initial diagnosis and surgery (160/167; 95.8%). Re-excision post IORT occurred in 16/167 patients (9.6%) due to positive margins. Adjuvant RT to the whole breast +/- LN was ultimately given to 23/167 (13.8%) patients mainly due to positive sentinel LN found on final pathology (12/23; 52%); other reasons were close margins for DCIS (3/23; 13%), tumor size (3/23; 4.3%), and multifactorial (5/23; 17.4%). Five patients (3%) had post-operative complications of wound dehiscence. There were 3 local recurrences (1.6%) at a median follow-up of 27.9 months (range: 0.7– 54.8 months). Conclusions: IORT has been proven to be a safe and patient-centered form of local adjuvant RT for our population, in whom compliance with a longer course of external beam radiation can be an issue. Long term efficacy remains to be evaluated through continued follow up. In the era of COVID-19 and beyond, IORT has been an increasingly attractive option, as it greatly minimizes toxicities and patient visits to the clinic. Trial Registration: All patients were prospectively enrolled on an institutional review board-approved registry trial (IRB number: 2018-9409).

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