Preoperative Helical Tomotherapy and Megavoltage Computed Tomography for Rectal Cancer: Impact on the Irradiated Volume of Small Bowel
- Department of Radiation Oncology, Oncologisch Centrum UZ Brussel, Brussels (Belgium)
- Department of Gastroenterology, Oncologisch Centrum UZ Brussel, Brussels (Belgium)
Purpose: Preoperative (chemo)radiotherapy is considered to be standard of care in locally advanced rectal cancer, but is associated with significant small-bowel toxicity. The aim of this study was to explore to what extent helical tomotherapy and daily megavolt (MV) CT imaging may reduce the irradiated volume of small bowel. Methods and Materials: A 3D-conformal radiotherapy (3D-CRT) plan with CTV-PTV margins adjusted for laser-skin marks (15, 15, and 10 mm for X, Y, and Z directions, respectively) was compared with helical tomotherapy (IMRT) using the same CTV-PTV margins, and to helical tomotherapy with margins adapted to daily MV-CT imaging (IMRT/IGRT; 8, 11, 7, and 10 mm for X, Y{sub ant}, Y{sub post} and Z resp.) for 11 consecutive patients. The planning goals were to prescribe 43.7 Gy to 95% of the PTV, while minimizing the volume of small bowel receiving more than 15 Gy (V{sub 15} {sub SB}). Results: The mean PTV was reduced from 1857.4 {+-} 256.6 cc to 1462.0 {+-} 222.3 cc, when the CTV-PTV margins were adapted from laser-skin marks to daily MV-CT imaging (p < 0.01). The V{sub 15} {sub SB} decreased from 160.7 {+-} 102.9 cc to 110.9 {+-} 74.0 cc with IMRT and to 81.4 {+-} 53.9 cc with IMRT/IGRT (p < 0.01). The normal tissue complication probability (NTCP) for developing Grade 2+ diarrhea was reduced from 39.5% to 26.5% with IMRT and to 18.0% with IMRT/IGRT (p < 0.01). Conclusion: The combination of helical tomotherapy and daily MV-CT imaging significantly decreases the irradiated volume of small bowel and its NTCP.
- OSTI ID:
- 21276946
- Journal Information:
- International Journal of Radiation Oncology, Biology and Physics, Journal Name: International Journal of Radiation Oncology, Biology and Physics Journal Issue: 5 Vol. 74; ISSN IOBPD3; ISSN 0360-3016
- Country of Publication:
- United States
- Language:
- English
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