A treatment planning study of prone vs. supine positions for locally
advanced rectal carcinoma
Comparison of 3-dimensional conformal radiotherapy, tomotherapy, volumetric modulated
arc therapy, and intensity-modulated radiotherapy
· Christopher Kittel
· Philipp Niermann
· Heidi Wolters
· Katharina Helene Susek
· Hans Theodor Eich
Received: 14 November 2017 / Accepted: 18 May 2018
© Springer-Verlag GmbH Germany, part of Springer Nature 2018
Purpose To ascertain the optimal radiation technique and radiation position for the neoadjuvant radiotherapy of patients
with rectal cancer.
Materials and methods Treatment plans with similar dose objectives were generated for 20 selected patients. Dosimetric
comparison was performed between prone and supine positions and between different radiation techniques. Dosimetric
indices for the target volume and organs at risk (OAR) as well as normal tissue complication probability (NTCP) of late
small bowel toxicity were analyzed.
Results The helical tomotherapy (HT) in the prone position provided the optimal dose homogeneity in the target volume
with the value of 0. Superior conformity values were obtained for Sliding Window (SW), Rapid Arc (RA) and HT compared
to three-dimensional conformal radiotherapy (3D-CRT) techniques. All of the techniques showed dose reduction to OAR
in the high-dose area in prone position versus supine position. Pairwise comparison revealed signiﬁcantly higher small
bowel protection by RA in the prone position in the high-dose area (V75, V45Gy). Similarly, superior bladder sparing
was found for 3D-CRT in the prone position at higher doses (V50, V75). More healthy tissue in the radiation volume was
involved by application of 3D-CRT with no relevant difference between positions. The mean values of NTCP for the small
bowel did not show clinically meaningful variation between the techniques.
Conclusion All techniques provided superior sparing of OAR in the prone position. At higher radiation doses, treatment
in prone position resulted in signiﬁcant OAR protection, especially concerning small bowel sparing by RA and bladder
sparing by 3D CRT.
Keywords Rectal carcinoma · Radiation position · Radiation technique · Sparing of organ at risk · Small bowel toxicity
S. Scobioala and C. Kittel contributed equally to this work.
Electronic supplementary material The online version of this
article (https://doi.org/10.1007/s00066-018-1324-0) contains
supplementary material, which is available to authorized users.
Sergiu Scobioala, M.D.
Department of Radiation Oncology of the University
of Muenster, Albert-Schweitzer-Campus 1,
Gebäude A1, 48149 Muenster, Germany