Background: The use of the belly board device (BBD) in the prone position has gained acceptance to spare small bowel in rectal cancer patients irradiated postoperatively, but there are few data in the preoperative setting, and the advantages of the BBD regarding normal tissue sparing may be counteracted by problems of patient positioning. This study was undertaken to investigate prospectively the influence of the BBD on treatment reproducibility in patients irradiated preoperatively in the prone position.
Patients and methods: 23 patients with rectal carcinoma in clinical stages II/III were included in this study. Axis displacement was evaluated in 14 patients treated without the BBD and nine with. The BBD is a commercial device (Belly Board, Radiation Products Design, Albertville, MN) made of a 17-cm thick hard sponge with an opening of 42 x 42 cm2. No specific patient immobilization devices were used. During radiotherapy, twelve patients had four control films, while eleven patients had three. The mean treatment position deviation was calculated for the medio-lateral, cranio-caudal and antero-posterior directions.
Results: When comparing the first control film to the corresponding simulation film for patients without the BBD and with the BBD, the mean lateral displacements were 1.5 mm and 3.2 mm (p = 0.26), the mean cranio-caudal displacements were 1.55 mm and 4.2 mm (p = 0.13), and the mean antero-posterior displacements were 1.8 mm and 4.5 mm (p = 0.04), respectively. When considering all control films, for the three directions, the amplitudes of the displacements were greater when using the BBD, particularly for the antero-posterior direction where the difference was highly significant (p = 0.0006).
Conclusions: Our data show that, in patients treated prone for rectal cancer, the use of the BBD in the preoperative setting without immobilization devices was associated with problems of patient position reproducibility, particularly for the antero-posterior direction. Thus, the use of patient immobilization devices and/or individual custom-made BBD may be recommended if a decision to treat the patient with a BBD is taken.