TY - JOUR
T1 - Impact of magnetic resonance-guided versus conventional radiotherapy workflows on organ at risk doses in stereotactic body radiotherapy for lymph node oligometastases
AU - Werensteijn-Honingh, Anita M
AU - Kroon, Petra S
AU - Winkel, Dennis
AU - van Gaal, J Carlijn
AU - Hes, Jochem
AU - Snoeren, Louk M W
AU - Timmer, Jaleesa K
AU - Mout, Christiaan C P
AU - Bol, Gijsbert H
AU - Kotte, Alexis N
AU - Eppinga, Wietse S C
AU - Intven, Martijn
AU - Raaymakers, Bas W
AU - Jürgenliemk-Schulz, Ina M
N1 - Funding Information:
This work was supported by the Dutch Cancer Society under Grant 2015-0848 .
Funding Information:
The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: The overarching University Medical Center Utrecht MR-linac scientific project, including employment of multiple authors, has been partly funded by Elekta AB (Stockholm, Sweden). Elekta did not have any part in the design, execution or analysis of this study. The authors declared that there is no other conflict of interest.
Publisher Copyright:
© 2022
PY - 2022/7
Y1 - 2022/7
N2 - Background and purpose: Magnetic resonance (MR)-linac delivery is expected to improve organ at risk (OAR) sparing. In this study, OAR doses were compared for online adaptive MR-linac treatments and conventional cone beam computed tomography (CBCT)-linac radiotherapy, taking into account differences in clinical workflows, especially longer session times for MR-linac delivery.Materials and methods: For 25 patients with pelvic/abdominal lymph node oligometastases, OAR doses were calculated for clinical pre-treatment and daily optimized 1.5 T MR-linac treatment plans (5 × 7 Gy) and compared with simulated CBCT-linac plans for the pre-treatment and online anatomical situation. Bowelbag and duodenum were re-contoured on MR-imaging acquired before, during and after each treatment session. OAR hard constraint violations, D
0.5cc and D
10cc values were evaluated, focusing on bowelbag and duodenum.
Results: Overall, hard constraints for all OAR were violated less often in daily online MR-linac treatment plans compared with CBCT-linac: in 5% versus 22% of fractions, respectively. D
0.5cc and D
10cc values did not differ significantly. When taking treatment duration and intrafraction motion into account, estimated delivered doses to bowelbag and duodenum were lower with CBCT-linac if identical planning target volume (PTV) margins were used for both modalities. When reduced PTV margins were achievable with MR-linac treatment, bowelbag doses were lower compared with CBCT-linac.
Conclusions: Compared with CBCT-linac treatments, the online adaptive MR-linac approach resulted in fewer hard planning constraint violations compared with single-plan CBCT-linac delivery. With respect to other bowelbag/duodenum dose-volume parameters, the longer duration of MR-linac treatment sessions negatively impacts the potential dosimetric benefit of daily adaptive treatment planning.
AB - Background and purpose: Magnetic resonance (MR)-linac delivery is expected to improve organ at risk (OAR) sparing. In this study, OAR doses were compared for online adaptive MR-linac treatments and conventional cone beam computed tomography (CBCT)-linac radiotherapy, taking into account differences in clinical workflows, especially longer session times for MR-linac delivery.Materials and methods: For 25 patients with pelvic/abdominal lymph node oligometastases, OAR doses were calculated for clinical pre-treatment and daily optimized 1.5 T MR-linac treatment plans (5 × 7 Gy) and compared with simulated CBCT-linac plans for the pre-treatment and online anatomical situation. Bowelbag and duodenum were re-contoured on MR-imaging acquired before, during and after each treatment session. OAR hard constraint violations, D
0.5cc and D
10cc values were evaluated, focusing on bowelbag and duodenum.
Results: Overall, hard constraints for all OAR were violated less often in daily online MR-linac treatment plans compared with CBCT-linac: in 5% versus 22% of fractions, respectively. D
0.5cc and D
10cc values did not differ significantly. When taking treatment duration and intrafraction motion into account, estimated delivered doses to bowelbag and duodenum were lower with CBCT-linac if identical planning target volume (PTV) margins were used for both modalities. When reduced PTV margins were achievable with MR-linac treatment, bowelbag doses were lower compared with CBCT-linac.
Conclusions: Compared with CBCT-linac treatments, the online adaptive MR-linac approach resulted in fewer hard planning constraint violations compared with single-plan CBCT-linac delivery. With respect to other bowelbag/duodenum dose-volume parameters, the longer duration of MR-linac treatment sessions negatively impacts the potential dosimetric benefit of daily adaptive treatment planning.
KW - Bowel
KW - CBCT-linac
KW - Duodenum
KW - Lymph node metastases
KW - MR-linac
KW - Stereotactic body radiotherapy
UR - https://www.scopus.com/pages/publications/85133683971
U2 - 10.1016/j.phro.2022.06.011
DO - 10.1016/j.phro.2022.06.011
M3 - Article
C2 - 35814260
SN - 2405-6316
VL - 23
SP - 66
EP - 73
JO - Physics and Imaging in Radiation Oncology
JF - Physics and Imaging in Radiation Oncology
ER -