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Abstract
Purpose: Positive margins after breast-conserving surgery are associated with poor oncological outcomes and warrant additional surgery. This study aimed to evaluate the effectiveness of high-dose radiation therapy for positive margins by comparing local recurrence between patients with positive and negative margins.

Methods: We retrospectively evaluated 550 patients treated with adjuvant radiation therapy after breast-conserving surgery for invasive breast cancer between 2013 and 2019. The total equivalent dose in 2 Gy fractions (EQD2) to the tumor bed ranged from 65.81 to 66.25 Gy for positive margins and 59.31-61.81 Gy for negative margins. The differences in local recurrence between the positive and negative margin groups were analyzed.

Results: After a median follow-up of 58 months, the crude local recurrence rate was 7.3% in the positive margin group (n = 55) and 2.4% in the negative margin group (n = 495). Positive margins were associated with higher local recurrence without statistical significance in the entire cohort (p = 0.062). Among patients aged <60 years, those with positive margins had a significantly lower 5-year local recurrence-free survival rate than those with negative margins (89.16% vs. 97.57%, respectively; p = 0.005). In contrast, there was no significant difference in the 5-year local recurrence-free survival rate between patients with positive and negative margins among those aged ≥60 years (100.00% vs. 94.38%, respectively; p = 0.426).

Conclusion: In this study, positive margins were not associated with poor local control in older patients after a high-dose boosts. Further prospective studies are needed to verify our findings.

Affiliations

Hyunjung Kim 1, Tae Gyu Kim 2, Byungdo Park 1, Jeong Ho Kim 1, Si-Youl Jun 3, Jun Ho Lee 3, Hee Jun Choi 3, Chang Shin Jung 3, Yoon Ju Bang 3, Hyoun Wook Lee 4, Jae Seok Lee 4, Hyun Yeol Nam 5, Seunghyeon Shin 5, Sung Min Kim 6, Haeyoung Kim 7
1Department of Radiation Oncology, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, Changwon, South Korea.
2Department of Radiation Oncology, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, Changwon, South Korea. Electronic address: tg1.kim@samsung.com.
3Department of Surgery, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, Changwon, South Korea.
4Department of Pathology, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, Changwon, South Korea.
5Department of Nuclear Medicine, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, Changwon, South Korea.
6Department of Internal Medicine, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, Changwon, South Korea.
7Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.