Targeted Intraoperative Radiotherapy Is Non-inferior to Conventional External Beam Radiotherapy in Chinese Patients With Breast Cancer: A Propensity Score Matching Study.

Yin Mi,Ruitai Fan,Qinchen Cao,Lele Liu,Yuanting Gu,Fang Wang,Lin Li,Pengwei Lv,Mingzhi Zhu,Meilian Dong,Yonggang Shi,Jingruo Li,Yingying Zhang,Xiaoxiao Zuo,Yanyan Wang

doi:10.3389/fonc.2020.550327

Abstract

Purpose: To investigate the efficacy of targeted intraoperative radiotherapy (TARGIT) vs. conventional external beam radiotherapy (EBRT) in Chinese patients with breast cancer.Methods: We retrospectively analyzed breast cancer patients who underwent breast-conserving surgery (BCS) at our hospital between April 2009 and October 2017. Patients were divided into TARGIT group and EBRT group according to different radiotherapy methods. TARGIT was performed with low-energy X-rays emitted by the Intrabeam system to deliver a single dose of 20 Gy to the applicator surface. Propensity score matching was performed at 1:1. The Kaplan–Meier method was used to calculate the locoregional recurrence (LR), distant metastasis-free survival (DMFS), disease-free survival (DFS), and overall survival (OS) of the two groups, and the log-rank test was run to analyse between-group difference before and after matching.Results: A total of 281 patients were included, with a median follow-up of 43 months. Of them, 82 were included in the TARGIT group and 199 in the EBRT group. Using the risk-adapted approach, 6.1% of patients received supplemental EBRT in the TARGIT group. The 5-year LR rate was 3.2% in the TARGIT group and 3.1% in the EBRT group (P = 0.694), the 5-year DMFS rates were 100 and 96.7%, respectively (P = 0.157); the 5-year DFS rates were 96.8 and 94.2% (P = 0.604); and the 5-year OS rates were 97.6 and 97.8% (P = 0.862). After matching which eliminated interference from imbalanced baseline factors, 128 matched patients were analyzed by the Kaplan–Meier method. The 5-year LR rate was 2.3% in the TARGIT group and 1.6% in the EBRT group; the 5-year DMFS rates were 100 and 98.4%, respectively; the 5-year DFS rates were 97.7 and 98.4%; and the 5-year OS rates were 98.4 and 98.4% (P = 0.659, 0.313, 0.659, 0.987). There was no significant difference in efficacy between TARGIT group and EBRT group.Conclusion: TARGIT and EBRT have similar 5-year outcomes in selected Chinese breast cancer patients undergoing BCS, and it can be used as an effective alternative to standard therapy, with substantial benefits to patients. The results need to be further confirmed by extending the follow-up time.

Highlights

In the beginning of the 21st century, long-term follow-up results of prospective studies such as the National Surgical Adjuvant Breast and Bowel Project B-06 study [1,2,3] showed that for patients with early breast cancer, breast-conserving surgery (BCS) combined with whole-breast external beam radiotherapy (EBRT) is similar to mastectomy with respect to relapse and survival
The exclusion criteria were as follows: (i) contraindication to radiotherapy or a previous history of radiotherapy in the breast region; (ii) collagen vascular disease; (iii) suspected polycentric lesions based on preoperative mammography, ultrasound, or MRI; (iv) distant metastasis indicated by imaging examination; (v) inflammatory breast cancer; (vi) positive resection margin after extensive local resection of the tumor and failure to ensure a negative margin on subsequent resection; (vii) suspected malignant microcalcification with extensive or diffusive distribution based on imaging; and (viii) pregnancy
82 were included in the TARGIT group and 199 in the EBRT group

Summary

Introduction

In the beginning of the 21st century, long-term follow-up results of prospective studies such as the National Surgical Adjuvant Breast and Bowel Project B-06 study [1,2,3] showed that for patients with early breast cancer, breast-conserving surgery (BCS) combined with whole-breast external beam radiotherapy (EBRT) is similar to mastectomy with respect to relapse and survival. Some researchers are trying to identify breast cancer patients who do not require postoperative radiotherapy. Based on the inclusion criteria of the Cancer and Leukemia Group B (CALGB) 9,343 and PRIME II studies, few elderly patients with early breast cancer who are eligible for standard endocrine therapy may not require radiotherapy, but they face increased risk of local relapse [12, 13]. Some researchers believe that EBRT may be an excessive treatment after BCS

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Discussion

Conclusion