Hybrid volumetric-modulated arc therapy for postoperative breast cancer including regional lymph nodes: the advantage of dosimetric data and safety of toxicities

Abstract

To improve the homogeneity and conformity of the irradiation dose for postoperative breast cancer including regional lymph nodes, we planned Hybrid volumetric-modulated arc therapy (VMAT), which combines conventional tangential field mainly for the chest area and VMAT mainly for the supraclavicular area and marginal zone. In this study, we compared the dosimetric impact between traditional 3D conformal radiotherapy (3DCRT) and Hybrid VMAT and observed toxicities following Hybrid VMAT. A total of 70 patients indicated between October 2016 and December 2017 were included. The prescribed dose was 50 Gy/25 fractions. For the dosimetric impact, 3DCRT and Hybrid VMAT plans were compared in each patient with respect to the dosimetric parameters. Toxicities were followed using the Common Terminology Criteria for Adverse Events version 4.0. The median follow-up duration was 319 days. For the dosimetric impact, the homogeneity index (HI) and conformity index (CI) of PTV were significantly improved in the Hybrid VMAT plan compared with that in the 3DCRT plan (HI, 0.15 ± 0.07 in Hybrid VMAT vs 0.41 ± 0.19 in 3DCRT, P < 0.001; CI, 1.61 ± 0.44 in Hybrid VMAT vs 2.10 ± 0.56 in 3DCRT, P < 0.001). The mean irradiated ipsilateral lung dose was not significantly different in both plans (12.0 ± 2.4 Gy in Hybrid VMAT vs 11.8 ± 2.8 Gy in 3DCRT, P < 0.533). Regarding toxicity, there were no patients who developed ≥grade 3 acute toxicity and ≥grade 2 pneumonitis during the follow-up. Hybrid VMAT for postoperative breast cancer including regional lymph nodes was a reasonable technique that improved the homogeneity and conformity of the irradiation dose to the planning target volume while keeping the irradiation dose to organs at risk to a minimum.

Impact of CBCT frequency on target coverage and dose to the organs at risk in adjuvant breast cancer radiotherapy

“…All patients treated in this study received VMAT, which provides a better PTV homogeneity and a lower dose to the OARs in breast cancer patients treated with RNI and SIB compared to 3D-plans 29 . Nevertheless, many patients are still treated with 3D-CRT and some centers use hybrid techniques combining tangential field irradiation and VMAT 30 . Our results are of only limited validity for these techniques, as the isodose distribution, especially in the heart and lungs, differ significantly between the techniques.…”

Retrospective evaluation of a robust hybrid planning technique established for irradiation of breast cancer patients with included mammary internal lymph nodes

“…In general, a large portion of the lung must be included in the irradiation field and the coverage of the supra clavicular lymph nodes (supra) as well as the MI LN is not optimal. Several studies [ 5 – 8 ] indicate, that a good sparing of the organs at risk (OARs), target coverage and conformity may be achieved by a pure volumetric modulated arc (VMAT) or hybrid planning technique where arcs and static intensity modulated (IMRT) fields are combined. Therefore, our clinic developed a hybrid planning technique that allows the necessary sparing of the OARs, target coverage and robustness with respect to swelling of the breast tissue during therapy.…”

Improved robustness in the junction region for postoperative breast cancer including supraclavicular nodes using hybrid VMAT

“…Several approaches have been proposed to improve inhomogeneities in the junction region [7][8][9][10][11][12][13][14][15][16][17][18]. Intensity-modulated radiation therapy (IMRT) or volumetric-modulated arc therapy (VMAT) for breast cancer treatment have been proposed to provide better dosimetric results and to improve dose conformity to the target [9][10][11][12][13][14][15][16][17][18]. Most hybrid VMAT planning studies for breast treatment have used either IMRT or VMAT, which uses open tangential threedimensional conformal radiotherapy (3D-CRT) elds with main dose weighting as a base dose plan [9][10][11][12][13][14].…”

“…Most hybrid VMAT planning studies for breast treatment have used either IMRT or VMAT, which uses open tangential threedimensional conformal radiotherapy (3D-CRT) elds with main dose weighting as a base dose plan [9][10][11][12][13][14]. We used a combination of two tangential elds with unequal cranial eld edges above the breast and VMAT elds to obtain a signi cant improvement in homogeneity and conformity for the targets, which is called "Hybrid VMAT" [18]. Our method differs from the one commonly referred to as the hybrid VMAT technique.…”

“…Studies analyzing IMRT or VMAT have used a virtual bolus outside the breast contour to ensure target dosage due to the lack of buildup and lateral scatter [20][21]. Our proposed hybrid VMAT plans provide better target coverage and dose homogeneity than that of the 3D-CRT plans, and proved to be a safe technique upon evaluating the toxicity [18]. However, in our method, the dose distribution in the junction region may be affected by patient motion.…”