The impact of patient positioning and use of belly board on small bowel toxicity in patients receiving pelvic radiotherapy for gynecological malignancies.

Aim: To determine the efficacy of belly board device in patients receiving postoperative radiation for gynecological malignancies in terms of setup error and acute small bowel toxicity.

Materials And Methods: Patients requiring postoperative radiation for gynecological malignancies were prospectively randomized to either treatment with supine position (supine arm) or prone position using belly board (prone arm). Each patient underwent computed tomography simulation in the assigned treatment position, and a three-dimensional conformal radiation was planned. Weekly two to three treatment sessions were verified using portal imaging and setup errors were noted. All patients were reviewed weekly to assess for symptoms and toxicity using a structured format. The systematic and random errors were calculated along the three axes.

Results: Twenty-four patients were randomized and 22 patients were available for the final analysis. The systematic error in supine arm versus prone arm was 3.9 versus 3.5 mm, 2.1 versus 4.8 mm and 3.1 versus 3.1 mm along lateral, antero-posterior (AP) and cranio-caudal (CC) direction. The random error in supine arm versus prone arm was 5 versus 3.9 mm, 2.9 mm versus 4.4 mm and 4.3 versus 3.4 mm along lateral, AP and CC direction. The calculated planning target volume margin for supine arm was 1.3, 0.7, and 1.0 cm and margin for prone arm was 1.1, 1.5, and 1.0 cm along lateral, AP, and CC direction, respectively. One patient in supine arm developed Grade 3 toxicity.

Conclusion: The systematic error and random error is more along AP direction for prone position. The acute small bowel toxicity was less using belly board.