Adjuvant Radiotherapy after Breast Conserving Treatment for Breast Cancer: A Dosimetric Comparison between Volumetric Modulated Arc Therapy and Intensity Modulated Radiotherapy.
BACKGROUND
Radiotherapy is an important treatment of choice for breast cancer patients after breast- conserving surgery, and we compare the feasibility of using dual arc volumetric modulated arc therapy (VMAT2), single arc volumetric modulated arc therapy (VMAT1) and Multi-beam Intensity Modulated Radiotherapy (M-IMRT) on patients after breast-conserving surgery.


METHODS
Thirty patients with breast cancer (half right-sided and half left-sided) treated by conservative lumpectomy and requiring whole breast radiotherapy with tumor bed boost were planned with three different radiotherapy techniques: 1) VMAT1; 2) VMAT2; 3) M-IMRT. The distributions for the planning target volume (PTV) and organs at risk (OARs) were compared. Dosimetries for all the techniques were compared.


RESULTS
All three techniques satisfied the dose constraint well. VMAT2 showed no obvious difference in the homogeneity index (HI) and conformity index (CI) of the PTV with respect to M-IMRT and VMAT1. VMAT2 clearly improved the treatment efficiency and can also decrease the mean dose and V5Gy of the contralateral lung. The mean dose and maximum dose of the spinal cord and contralateral breast were lower for VMAT2 than the other two techniques. The very low dose distribution (V1Gy) of the contralateral breast also showed great reduction in VMAT2 compared with the other two techniques. For the ipsilateral lung of right-sided breast cancer, the mean dose was decreased significantly in VMAT2 compared with VMAT1 and M-IMRT. The V20Gy and V30Gy of the ipsilateral lung of the left- sided breast cancer for VMAT2 showed obvious reduction compared with the other two techniques. The heart statistics of VMAT2 also decreased considerably compared to VMAT1 and M-IMRT.


CONCLUSIONS
Compared to the other two techniques, the dual arc volumetric modulated arc therapy technique reduced radiation dose exposure to the organs at risk and maintained a reasonable target dose distribution.
Department of Radiation Oncology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China E-mail : sunxinchen2012@163.com; chenjiayan2008@126.com.
Zhe-Ming
ZM
Liu
Xiao-Lin
XL
Ge
Jia-Yan
JY
Chen
Pei-Pei
PP
Wang
Chi
C
Zhang
Xi
X
Yang
Hong-Cheng
HC
Zhu
Jia
J
Liu
Qin
Q
Qin
Li-Ping
LP
Xu
Jing
J
Lu
Liang-Liang
LL
Zhan
Hong-Yan
HY
Cheng
Xin-Chen
XC
Sun
D001943:Breast Neoplasms / Q000532:radiotherapy; D005260:Female; D006801:Humans; D015412:Mastectomy, Segmental; D058958:Organs at Risk; D011874:Radiometry; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D018714:Radiotherapy, Adjuvant / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012189:Retrospective Studies; D000069584:Unilateral Breast Neoplasms / Q000532:radiotherapy*