Dislocation of small bowel volume within box pelvic treatment fields, using new "up down table" device

Purpose: To present the impact of a novel minimization device, the up down table (UDT), on the volume of small bowel included within a 4-field pelvic irradiation plan. Methods: A polystyrene bowel displacement standard mold was created and added to a customized vacuum cushion (Nac Lok) formed around the abdomen and legs of each patient in the prone position. Two hundred seventy-seven consecutive patients with pelvic malignancies treated with the UDT device were compared with I historic series (68 cases) treated at our division. Small bowel contrast dyes at the time of simulation were used in all patients. Results: The average volume of small bowel within the planning target volume (high-dose volume, calculated with Gallagher method) was 100 cm(3) (median 49 +/- 114) in the series treated with standard box technique and 23 cm(3) (median 0 +/- 64) in the series treated with the UDT (p < 0.001). The average volume of small bowel included in any isodose (any-dose volume) was 505 cm(3) (median 447 +/- 338) and 1558 cm(3) (median 69 +/- 207), respectively (p < 0.001). The incidence of G1, G2, and G3 acute enteric toxicity (Radiation Therapy Oncology Group criteria) in the UDT series was 16%, 15%, and 1.5%; in the standard box technique, it was 28%, 25%, and 3%, respectively (p < 0.05). The incidence of acute enteric toxicity directly correlated with the irradiated small bowel volume. In the UDT series, the 5-year actuarial incidence of G3 chronic enteric toxicity was 1.8%. The setup procedures, analyzed in 18 cases, revealed no systematic errors and a standard deviation equal to +/-5 nun for random errors. Conclusions: The UDT technique is comfortable, inexpensive, highly reproducible, and permits an almost full bowel displacement from standard radiotherapy fields. (C) 2001 Elsevier Science Inc.