External-beam partial breast irradiation in a supine versus prone position after breast-conserving surgery for Chinese breast cancer patients

Ting Yu,Wei Wang,Xijun Liu,Qian Shao,Tao Sun,Min Xu,Fengxiang Li,Jian Bin Li,Yingjie Zhang

doi:10.1038/s41598-018-33741-z

Abstract

To investigate the differences in target volumes and dosimetric parameters between the supine and prone positions for external-beam partial breast irradiation (EB-PBI) after breast-conserving surgery (BCS) for Chinese breast cancer patients, thirty breast cancer patients who underwent three-dimensional conformal radiation therapy (3DCRT) EB-PBI after BCS were enrolled. Supine and prone scan sets were acquired during free breathing for all patients. Target volumes and organs at risk (OARs) including the heart, ipsilateral lung and bilateral breast were contoured by the same radiation oncologist. For each patient, supine and prone EB-PBI plans were generated based on the same planning criteria. The clinical target volume (CTV) and planning target volume (PTV) in the prone position were significantly greater than those in the supine position (P = 0.003, 0.004, respectively). A 0.95 Gy reduction in the mean dose (Dmean) to the heart (P = 0.000) was apparent in the supine position compared to the prone position. The Dmean to the ipsilateral lung was significantly lower in the prone position than in the supine position (1.59 Gy vs. 1.72 Gy, P = 0.029). Therefore, for Chinese breast cancer patients, carrying out 3DCRT EB-PBI in the prone position during free breathing is feasible.

Highlights

Breast-conserving therapy (BCT) has become a standard of care in the treatment of early-stage breast cancer, and radiotherapy after breast-conserving surgery (BCS) plays an important role in BCT
Thirty early-stage breast cancer patients who had undergone BCS and were potentially eligible for external-beam partial breast irradiation (PBI) (EB-PBI) were enrolled in this study
This difference might be caused by the different gross target volume (GTV) delineation criteria, whereby the seroma moves away from the chest wall due to gravity in the prone position; we delineated the GTV only based on the surgical clips

Summary

Introduction

Breast-conserving therapy (BCT) has become a standard of care in the treatment of early-stage breast cancer, and radiotherapy after breast-conserving surgery (BCS) plays an important role in BCT. The authors reported that prone breast irradiation reduced the radiation exposure dose to the lung and relieved the acute reaction of the skin, in patients with large and pendulous glands. Several dosimetric studies[8,9] have reported that, compared to conventional supine breast irradiation, the mean dose (Dmean) and volumes that receive equal or more than 20 Gy to the lung are decreased remarkably in prone breast irradiation after www.nature.com/scientificreports/. The prone positioning of patients during whole breast radiation (WBI) can improve dose homogeneity and reduce the high dose distribution in the target[12,13]. Based on these reports, prone breast irradiation has received a great deal of attention. In this study, we compared the EB-PBI treatment plans in the prone versus supine positions, and our emphasis was on investigating the differences in the volumetric and dosimetric parameters for EB-PBI in the two positions

Methods

Results

Discussion

Conclusion