Linear energy transfer distributions in the brainstem depending on tumour location in intensity-modulated proton therapy of paediatric cancer

Authors

  • Lars Fredrik Fjæra Department of Physics and Technology, University of Bergen, Bergen, Norway; ;Department of Oncology and Medical Physics, Haukeland University Hospital, Bergen, Norway
  • Zuofeng Li Department of Radiation Oncology, University of Florida, Jacksonville, FL, USA
  • Kristian S. Ytre-Hauge Department of Physics and Technology, University of Bergen, Bergen, Norway
  • Ludvig P. Muren Department of Medical Physics, Aarhus University/Aarhus University Hospital, Aarhus, Denmark
  • Daniel J. Indelicato Department of Radiation Oncology, University of Florida, Jacksonville, FL, USA
  • Yasmin Lassen-Ramshad Department of Oncology, Aarhus University Hospital, Aarhus, Denmark
  • Grete May Engeseth Department of Oncology and Medical Physics, Haukeland University Hospital, Bergen, Norway
  • Marianne Brydøy Department of Oncology and Medical Physics, Haukeland University Hospital, Bergen, Norway
  • Andrea Mairani Medical Physics Unit, CNAO Foundation, Pavia, Italy; ;Heidelberg Ion Beam Therapy Center (HIT), Heidelberg, Germany
  • Stella Flampouri Department of Radiation Oncology, University of Florida, Jacksonville, FL, USA
  • Olav Dahl Department of Oncology and Medical Physics, Haukeland University Hospital, Bergen, Norway
  • Camilla H. Stokkevåg Department of Oncology and Medical Physics, Haukeland University Hospital, Bergen, Norway

DOI:

https://doi.org/10.1080/0284186X.2017.1314007

Abstract

Background: For tumours near organs at risk, there is concern about unintended increase in biological dose from elevated linear energy transfer (LET) at the distal end of treatment fields. The objective of this study was therefore to investigate how different paediatric posterior fossa tumour locations impact LET and biological dose to the brainstem during intensity-modulated proton therapy (IMPT).

Material and methods: Multiple IMPT plans were generated for four different simulated tumour locations relative to the brainstem for a five-year-old male patient. A prescribed dose of 59.4 Gy(RBE) was applied to the planning target volumes (PTVs). Plans with two lateral and one posterior non-coplanar fields were created, along with plans with modified field arrangements. The dose-averaged LET (LETd) and the physical dose × RBELET (D × RBELET), where RBELET=1+c × LETd, were calculated using the FLUKA Monte Carlo code. A scaling parameter c was applied to make the RBELET represent variations in the biological effect due to LET.

Results: High LETd values surrounded parts of the PTV and encompassed portions of the brainstem. Mean LETd values in the brainstem were 3.2–6.6 keV/μm. The highest absolute brainstem LETd values were seen with the tumour located most distant from the brainstem, whereas lower and more homogeneous LETd values were seen when the tumour invaded the brainstem. In contrast, the highest mean D × RBELET values were found in the latter case (54.0 Gy(RBE)), while the case with largest distance between tumour and brainstem had a mean D × RBELET of 1.8 Gy(RBE).

Conclusions: Using IMPT to treat posterior fossa tumours may result in high LETd values within the brainstem, particularly if the tumour volume is separated from the brainstem. However, the D × RBELET was greater for tumours that approached or invaded the brainstem. Changing field angles showed a reduction of LETd and D × RBELET in the brainstem.

Downloads

Download data is not yet available.

Downloads

Additional Files

Published

2017-05-04

How to Cite

Fredrik Fjæra, L. ., Li, Z. ., Ytre-Hauge, K. S. ., Muren, L. P. ., Indelicato, D. J. ., Lassen-Ramshad, Y. ., … Stokkevåg, C. H. . (2017). Linear energy transfer distributions in the brainstem depending on tumour location in intensity-modulated proton therapy of paediatric cancer. Acta Oncologica, 56(6), 763–768. https://doi.org/10.1080/0284186X.2017.1314007

Issue

Vol. 56 No. 6 (2017): Acta Oncologica

Section

Articles