• Gowoon Yang, Jun Won Kim, Ik Jae Lee, Joon Jeong, Sung Gwe Ahn, Soong June Bae, Jee Hung Kim, and Yeona Cho.
• Department of Radiation Oncology, Yonsei Cancer Center, Heavy Ion Therapy Research Institute, Yonsei University College of Medicine, Seoul, Korea.
• Yonsei Med. J. 2024 Mar 1; 65 (3): 129136129-136.

PurposeThis study aimed to assess the feasibility and safety of administering intraoperative radiotherapy (IORT) as a boost during breast-conserving surgery (BCS) following neoadjuvant chemotherapy for patients at high risk of breast cancer recurrence.Materials And MethodsPatients who underwent neoadjuvant chemotherapy received a single 20-Gy dose of IORT during BCS, followed by external beam radiotherapy 4-6 weeks after surgery.ResultsThe median follow-up duration was 31.0 months (range, 18.0-59.0 months). Initial tumor sizes had a median of 2.6 cm (range: 0.8-5.3 cm), reducing to 0.3 cm (range: 0-4.0 cm) after neoadjuvant chemotherapy. The most common neoadjuvant chemotherapy regimen was doxorubicin and cyclophosphamide, followed by paclitaxel (n=42, 73.7%). Among 57 patients who received neoadjuvant chemotherapy before BCS and IORT, 2 patients (3.5%) required secondary surgery to achieve negative resection margins due to initially positive margins. Regional lymph node irradiation was performed in 37 (64.9%) patients. There was no grade 3 or higher adverse events, with 4 patients (7.0%) experiencing grade 2 acute radiation dermatitis and 3 (5.3%) having less than grade 2 breast edema. Binary correlation analysis did not reveal statistically significant associations between applicator size or radiation therapy modality and the risk of treatment-related toxicity. Furthermore, chi-square analysis showed that the grade of treatment-related toxicity was not associated with the fractionated regimen (p=0.375).ConclusionMost patients successfully received IORT as a tumor bed boost after neoadjuvant chemotherapy. Thus, IORT may be a safe and feasible option for patients with advanced-stage breast cancer receiving neoadjuvant chemotherapy.© Copyright: Yonsei University College of Medicine 2024.

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