Hybrid VMAT-3DCRT as breast cancer treatment improvement tool.

Radiation therapy is an important tool in the treatment of breast cancer and can play a crucial role in improving patient outcomes. For breast cancer, if the technique has been for a long time the use of 3DCRT, clinicians have seen the management evolve greatly in recent years. Field-in-field and IMRT approaches and more recently dynamic arctherapy are increasingly available. All of these approaches are constantly trying to improve tumour coverage and to preserve organs at risk by minimising the doses delivered to them. If arctherapy allows a considerable reduction of high doses received by healthy tissues, no one can deny that it also leads to an increase of low doses in tissues that would not have received any with other techniques. We propose a hybrid approach combining the robustness of the 3DCRT approach and the high technicality and efficiency of arctherapy. Statistical tests (ANOVA, Wilcoxon, determination coefficient, ROC, etc.) allow us to draw conclusions about the possibility of using the hybrid approach in certain cases (right breast, BMI [Formula: see text], age [Formula: see text], target volume [Formula: see text] cc, etc.). Depending on the breast laterality and patients morphological characteristics, hybridization may prove to be a therapeutic tool of choice in the management of breast cancer in radiotherapy.

Safety and benefit of using a virtual bolus during treatment planning for breast cancer treated with arc therapy.

PURPOSE: This study evaluates the benefit of a virtual bolus method for volumetric modulated arc therapy (VMAT) plan optimization to compensate breast modifications that may occur during breast treatment. METHODS: Ten files were replanned with VMAT giving 50 Gy to the breast and 47 Gy to the nodes within 25 fractions. The planning process used a virtual bolus for the first optimization, then the monitors units were reoptimized without bolus, after fixing the segments shapes. Structures and treatment planning were exported on a second scanner (CT) performed during treatment as a consequence to modifications in patient's anatomy. The comparative end-point was clinical target volume's coverage. The first analysis compared the VMAT plans made using the virtual bolus method (VB-VMAT) to the plans without using it (NoVB-VMAT) on the first simulation CT. Then, the same analysis was performed on the second CT. Finally, the level of degradation of target volume coverage between the two CT using VB-VMAT was compared to results using a standard technique of forward-planned multisegment technique (Tan-IMRT). RESULTS: Using a virtual bolus for VMAT does not degrade dosimetric results on the first CT. No significant result in favor of the NoVB-VMAT plans was noted. The VB-VMAT method led to significant better dose distribution on a second CT with modified anatomies compared to NoVB-VMAT. The clinical target volume's coverage by 95% (V95%) of the prescribed dose was 98.9% [96.1-99.6] on the second CT for VB-VMAT compared to 92.6% [85.2-97.7] for NoVB-VMAT (P = 0.0002). The degradation of the target volume coverage for VB-VMAT is not worse than for Tan-IMRT: the median differential of V95% between the two CT was 0.9% for VMAT and 0.7% for Tan-IMRT (P = 1). CONCLUSION: This study confirms the safety and benefit of using a virtual bolus during the VMAT planning process to compensate potential breast shape modifications.