Comparison of Heart and Lung Doses According to Tumor Bed Boost Techniques in Early-Stage Left-Sided Breast Cancer: Simultaneous Integrated Boost versus Sequential Boost

Abstract

Background and Objectives: The boost dose to the tumor bed after whole breast irradiation (WBI) can be divided into sequential boost (SEQ) and simultaneous integrated boost (SIB). SIB using modern radiation therapy (RT) techniques, such as volumetric modulated arc therapy, allow the delivery of a highly conformal dose to the target volume and has a salient ability to spare at-risk organs. This study aimed to compare the radiation dose delivered to the heart and lungs according to boost technique and tumor bed location. Materials and Methods: RT planning data of 20 patients with early-stage left-sided breast cancer were used in this study. All patients were treated with volumetric modulated arc therapy after breast-conserving surgery with a sentinel lymph node biopsy. For each patient, two different plans, whole breast irradiation with simultaneous integrated boost (WBI-SIB) and sequential boost after WBI (WBI-SEQ), were generated. To compare the dose received by each organ at risk (OAR), dose-volume histogram data were analyzed. The mean dose (Dmean) and volume of each organ that received x Gy (Vx) were calculated and compared. Results: For the heart, the V10 was lower for the WBI-SIB plan than for the WBI-SEQ plan (5.223 ± 1.947% vs. 6.409 ± 2.545%, p = 0.008). For the left lung, the V5 was lower in the WBI-SIB plan than for the WBI-SEQ plan (27.385 ± 3.871% vs. 32.092 ± 3.545%, p < 0.001). The Dmean for the heart and left lung was lower for the WBI-SIB plan than for the WBI-SEQ plan (heart: 339.745 ± 46.889 cGy vs. 413.030 ± 52.456 cGy, p < 0.001; left lung: 550.445 ± 65.094 cGy vs. 602.270 ± 55.775 cGy, p < 0.001). Conclusions: The WBI-SIB plan delivered lower radiation doses to the heart and left lung than the WBI-SEQ plan in terms of Dmean and low-dose volume in hypofractionated RT of early-stage left-sided breast cancer patients. Furthermore, a large radiation dose per day may be advantageous, considering the radiobiologic aspects of breast cancer. Long-term follow-up data are needed to determine whether the dosimetric advantages of the WBI-SIB plan can lead to clinically improved patient outcomes and reduced late side effects.

Hypofractionated wholebreast irradiation with sequential or simultaneous integrated boost for early breast cancer after-surgery treatment

“…In our study, we found that the SIB plan signi cantly reduced V5, V10, V15, V30, and V40 compared to the SEQ plan, indicating its superiority in reducing low-dose exposure to normal lung tissue. This aligns with the ndings from Kim et al [15]. Additionally, we observed a decrease in Dmean for the left lung in the SIB plan compared to the SEQ plan, consistent with previous research.…”

“…At the same time, the PTVtb was 49.6 Gy, (total of 16 fractions). The PTV prescription dose of the SEQ H-VMAT plan for WB was 42.5 Gy, a total of 16 fractions, followed by 4 fractions consecutive increase doses in PTV for TB, with 2.66 Gy for each fraction [15]. According to the prescription dose requirements and organ-endangering dose limitations, at least 95% of PTVs are required to reach the prescribed dose, optimizing the irradiation dose for the whole heart, atrium, ventricle, coronary artery, heart valve, lung, spinal cord, and contralateral breast.…”