Supine vs Prone Positioning without Belly Board for Rectal Cancer : A Practical Dosimetric Study in a Resource-limited Setting
Karima Mouden *
Department of Radiation Oncology, National Oncology Institute, Rabat, Morocco.
Soufiane Berhili
Department of Radiation Oncology, National Oncology Institute, Rabat, Morocco.
Fatima Assaoui
Department of Radiation Oncology, National Oncology Institute, Rabat, Morocco.
Tayeb Kebdani
Department of Radiation Oncology, National Oncology Institute, Rabat, Morocco.
Hanan El Kacemi
Department of Radiation Oncology, National Oncology Institute, Rabat, Morocco.
Sanaa Majjaoui
Department of Radiation Oncology, National Oncology Institute, Rabat, Morocco.
Noureddine Benjaafar
Department of Radiation Oncology, National Oncology Institute, Rabat, Morocco.
*Author to whom correspondence should be addressed.
Abstract
Background: This study aimed to evaluate the impact of patient positioning on dose distribution to the bowel and bladder in rectal cancer patients in a setting without access to a belly board or advanced techniques such as Intensity-Modulated Radiotherapy (IMRT).
Methods: Between July and October 2014, 20 consecutive rectal cancer patients were prospectively enrolled. Computed Tomography (CT) simulations were performed with a full bladder in two positions: prone (without a belly board) and supine. Three-dimensional conformal radiotherapy (3D-CRT) plans delivering 46 Gy in 23 fractions were generated. Bowel volumes receiving 5-Gy increments (V5–V45) and bladder dose parameters were compared between positions.
Results: The mean Planning Target Volume (PTV), bowel, and bladder volumes were similar between prone and supine positions (PTV: 1000.78 vs 1006.21 cm³, p=0.84; bowel: 752.04 vs 750.32 cm³, p=0.97; bladder: 225.48 vs 244.16 cm³, p=0.26). Across all dose levels (V5–V45), no statistically significant differences were observed in bowel or bladder irradiation.
Conclusion: Although these findings do not introduce new dosimetric concepts, they provide practical evidence supporting the use of the supine position with a full bladder in preoperative 3D-CRT for rectal cancer, particularly in centers lacking a belly board or access to IMRT. Supine positioning offers comparable bowel sparing, improved patient comfort, and better reproducibility, making it a feasible alternative in resource-limited settings.
Keywords: Bladder dose, bowel dose, dose–volume histogram, prone position, rectal cancer, resource-limited setting, supine position, 3D-CRT