Modified Volumetric Modulated Arc Therapy in Left Sided Breast Cancer After Radical Mastectomy With Flattening Filter Free Versus Flattened Beams

Abstract

Conventional volumetric modulated arc therapy (C-VMAT) for breast cancer after radical mastectomy had its limitation that resulted in larger volumes of normal tissue receiving low doses. We explored whether there was a way to deal with this disadvantage and determined the potential benefit of flattening filter-free (FFF) beams.Twenty patients with breast cancer after radical mastectomy were subjected to 3D conformal radiotherapy (3DCRT) and VMAT treatment planning. For VMAT plans, 3 different designs were employed with RapidArc form: conventional-VMAT plan (C-VMAT), modified-VMAT plan (M-VMAT), and modified-VMAT plan using FFF beams (M-VMAT-F). Plan quality and efficiency were assessed for all plans.For each technique in homogeneity, there were no statistically significant differences. VMAT plans showed superiority compared with 3DCRT in conformity. C-VMAT plans were obviously not only superior to 3DCRT in the medium to high-dose regions (about 15–50 Gy) but also resulted in larger volumes in low-dose regions (about 0–10 Gy). M-VMAT plans were similar to M-VMAT-F. Both of them might significantly reduce the regions of low dose compared with C-VMAT (V5lung: ∼ 11.5%; V5heart: ∼ 23.8%, P < 0.05), even less than 3DCRT in heart irradiation (V2.5heart, 9.4%, P < 0.05). For liver, contralateral breast, and lung irradiation, M-VMAT-F plans were slightly superior to M-VMAT with a reduction of ∼0.08, 0.2, and 0.24 Gy in the respective mean doses (P < 0.05).C-VMAT plans showed superiority compared with 3DCRT, while also resulted in larger volumes of normal tissue receiving low doses. M-VMAT and M-VMAT-F plans might not only reduce the region in the medium to high doses but also have lower volumes in low-dose regions. M-VMAT-F plans were slightly superior compared with M-VMAT due to further contralateral organs sparing.

Dosimetric Comparison of Three Radiotherapy Techniques in Irradiation of Left-Sided Breast Cancer Patients after Radical Mastectomy

“…2.6. Plan Optimization and Dose criteria [10,14]. In TSPs, all segmental targets were given the same objectives and cooptimized together.…”

“…The selection of the optimal radiation-delivery technique remains a critical component to individualize the breast cancer treatment, which requires adequate dose coverage as well as OARs sparing for each patient's unique anatomy. Compared to IMRT/VMAT plans, 3DCRT plans tend to have inferior targets coverage, poorer dose conformity, and higher volume of 20 Gy irradiation [10]. The IMRT and VMAT techniques for treating chest wall and regional nodes as a whole PTV after modified radical mastectomy have proven beneficial [5,6,9], such as better dose conformity and homogeneity.…”

The impact of the field width on VMAT plan quality and the assessment of half field method

“…We used a similar approach that has been investigated with flattening filter free beams for breast cancer to create half fields. 10 We define the following methods: three full field (3ff), four full field (4ff), three half field (3hf), four half field (4hf). The number in the names of the plans refers to the number of rotations used.…”

“…2). Each PTV had a different diameter (7,10,13,16,19,22,25,28,31,34, 37, 40 cm) and located at the center of the virtual phantom. For each PTV, two OAR contours (will be regarded as a single parallel organ both in the optimization and the dose calculation process) were created at the anterior and posterior sides of the PTV and located so that their center is on the border of the PTV contour.…”

Volumetric modulated arc therapy (VMAT) for hippocampal-avoidance whole brain radiation therapy: planning comparison with Dual-arc and Split-arc partial-field techniques

“…Until recently, several researchers have employed both split-arc and partial-field technique together to eliminate scatter radiation and MLC limitations in VMAT planning. This technique is beneficial in sparing adjacent OARs in breast cancer [26], cervical [27,28], anal [28,29], and vaginal cancer [28]. To the best of the author's knowledge, the formal literature is devoid of any reference to the application of both split-arc and partial-field technique in VMAT (sapf-VMAT) for WBRT with hippocampal sparing.…”