Outcomes of Breast Intraoperative Electron Beam Radiotherapy (IOeRT) : Case Series of Single Institute Experience in Saudi Arabia.

Introduction: 85-90% of local recurrences after breastconserving surgery occurs within the index quadrant. Intraoperative radiotherapy may be a good alternative for eligible patients avoiding long course of adjuvant radiation.

Patients and methods: Eligible patients were early stage node negative at least 50 years at time of inclusion, unicentric less than 30mm in diameter any hormone receptor status. 21 Gy was delivered intraoperatively, biologically equivalent to 58 to 60 Gy in standard fractionation using electron beam to 90% isodose line. Cosmetic, Oncological and Patient Satisfaction Evaluation of treated Patients between March 2018 and August 2020 at the King Khalid university hospital, using the IOeRT (Mobetron® ). Evaluation done at a combined clinic between surgical and radiation oncology teams at the end of the follow up period before publication.

Results: 15 female patients were evaluable with mean follow up period 33.8 months (19-48 months). Mean Age 56.4 years (50-65 years). Mean tumor size 1.213 cm. Majority of patients were T1. 2 patients showed Sentinel lymph node positive.21 Gy was delivered intraoperatively.4 Patients (26.7%) received adjuvant postoperative external beam radiation therapy (EBRT). 2 patients due to being in Caution group due to positive extensive Ductal carcinoma in situ (DCIS). External beam radiation was 40 Gy/15 fractions/3 weeks using three dimensional radiation therapy (3DCRT). Cosmetically, Apart from one patient score 9 due to presence of keloid scar formation, most patients were in range of 0-3 according to physician evaluation and Modified Hollander's score otherwise, No more than score 3 in any of the patients was detected. Oncologically, Till the time of publication no local or distant relapses was detected. As a patient experience, 100 % of patients were satisfied.

Conclusion: Breast IOERT is a convenient, safe and a valid treatment modality as an option for patients who are otherwise appropriate candidates for APBI. Proper patient selection should focus on clinicopathologic factors predictive of negative nodes and negative margins. Careful assessment of preoperative mammographic and other imaging studies for features, such as extent of calcifications, may be helpful.