Locoregional breast radiotherapy including IMN: optimizing the dose distribution using an automated non-coplanar VMAT-technique

Authors

  • Jomar Frengen a Department of Radiotherapy, Cancer Clinic, St. Olavs Hospital, Trondheim, Norway
  • Johan Vikström b Department of Radiotherapy, Stavanger University Hospital, Stavanger, Norway
  • Ingvil Mjaaland b Department of Radiotherapy, Stavanger University Hospital, Stavanger, Norway
  • Marit Funderud a Department of Radiotherapy, Cancer Clinic, St. Olavs Hospital, Trondheim, Norway
  • Sigrun Saur Almberg a Department of Radiotherapy, Cancer Clinic, St. Olavs Hospital, Trondheim, Norway
  • Kjell Ivar Dybvik b Department of Radiotherapy, Stavanger University Hospital, Stavanger, Norway
  • Mari Helene Blihovde Hjelstuen b Department of Radiotherapy, Stavanger University Hospital, Stavanger, Norway

DOI:

https://doi.org/10.1080/0284186X.2023.2264488

Keywords:

Radiotherapy, VMAT, locoregional breast, automation, IMN

Abstract

Background

Volumetric Modulated Arc Therapy (VMAT) offers better conformity, homogeneity and sparing of the heart and ipsilateral lung for locoregional radiotherapy in left-sided breast cancer compared to three-dimensional conformal radiotherapy (3D-CRT). However, conventional coplanar VMAT (cVMAT) can result in higher doses to the normal tissue on the contralateral side. This study investigates a non-coplanar VMAT-technique (ncVMAT) to mitigate this issue.

Material and methods

CT series of 20 left sided breast cancer patients were included for planning of locoregional breast radiotherapy including internal mammary nodes (IMN). Three treatment plans; 3D-CRT, cVMAT and ncVMAT, were generated for each patient with a prescription dose of 40.05 Gy in 15 fractions. Both VMAT-techniques consisted of a single arc in the axial plane, while ncVMAT included an additional arc in the sagittal plane. All plans were optimized to cover the clinical target volume (CTV) by 38.05 Gy for the breast and 36.05 Gy for lymph nodes, with as low as possible dose to organs at risk.

Results

Full CTV coverage was achieved for all plans. Both cVMAT and ncVMAT delivered more conformal and homogeneous target doses than 3D-CRT. Doses to the heart and ipsilateral lung were significantly lower with ncVMAT compared to both cVMAT and 3D-CRT. ncVMAT reduced doses to both the contralateral breast and lung compared to cVMAT and achieved levels similar to 3D-CRT for the contralateral breast and moderately higher doses for the contralateral lung. Delivery of high doses (>30 Gy) to the contralateral side was completely avoided with ncVMAT, contrary to the results for cVMAT and 3D-CRT.

Conclusion

ncVMAT reduced doses to the heart and ipsilateral lung as compared to both cVMAT and 3D-CRT. All contralateral dose metrics were reduced with the novel ncVMAT technique compared to cVMAT, and the mean contralateral breast doses were similar to 3D-CRT.

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Published

2023-10-03

How to Cite

Frengen, J., Vikström, J., Mjaaland, I., Funderud, M., Saur Almberg, S., Ivar Dybvik, K., & Blihovde Hjelstuen, M. H. (2023). Locoregional breast radiotherapy including IMN: optimizing the dose distribution using an automated non-coplanar VMAT-technique. Acta Oncologica, 62(10), 1169–1177. https://doi.org/10.1080/0284186X.2023.2264488

Issue

Vol. 62 No. 10 (2023): Acta Oncologica

Section

Articles