Comparison of inverse-planned three-dimensional conformal radiotherapy and intensity-modulated radiotherapy for non–small-cell lung cancer

• Published in: International journal of radiation oncology, biology, physics Vol. 67; no. 3; pp. 735 - 741
• Main Authors: Christian, Judith A., M.R.C.P., F.R.C.R., M.D, Bedford, James L., Ph.D, Webb, Steve, D.Sc., Ph.D, Brada, Michael, F.R.C.R., F.R.C.P
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-03-2007
• Subjects: ALGORITHMS; BEAMS; Carcinoma, Non-Small-Cell Lung - diagnostic imaging; Carcinoma, Non-Small-Cell Lung - radiotherapy; CARCINOMAS; COMPUTERIZED TOMOGRAPHY; Hematology, Oncology and Palliative Medicine; Humans; Intensity-modulated radiotherapy; Inverse planning; Lung - diagnostic imaging; Lung Neoplasms - diagnostic imaging; Lung Neoplasms - radiotherapy; LUNGS; Non–small-cell lung cancer; PATIENTS; PLANNING; PNEUMONITIS; RADIATION DOSES; Radiology; RADIOLOGY AND NUCLEAR MEDICINE; RADIOTHERAPY; Radiotherapy Dosage; Radiotherapy Planning, Computer-Assisted - methods; Radiotherapy, Conformal - methods; Radiotherapy, Intensity-Modulated - methods; Tomography, X-Ray Computed; Non–small-cell lung cancer; Inverse planning; Intensity-modulated radiotherapy
• ISSN: 0360-3016; 1879-355X
• DOI: 10.1016/j.ijrobp.2006.09.047

Purpose: Lungs are the major dose-limiting organ during radiotherapy (RT) for non–small-cell lung cancer owing to the development of pneumonitis. This study compared intensity-modulated RT (IMRT) with three-dimensional conformal RT (3D-CRT) in reducing the dose to the lungs. Methods: Ten patients with localized non–small-cell lung cancer underwent computed tomography (CT). The planning target volume (PTV) was defined and the organs at risk were outlined. An inverse-planning program, AutoPlan, was used to design the beam angle-optimized six-field noncoplanar 3D-CRT plans. Each 3D-CRT plan was compared with a series of five IMRT plans per patient. The IMRT plans were created using a commercial algorithm and consisted of a series of three, five, seven, and nine equidistant coplanar field arrangements and one six-field noncoplanar plan. The planning objectives were to minimize the lung dose while maintaining the dose to the PTV. The percentage of lung volume receiving >20 Gy (V20 ) and the percentage of the PTV covered by the 90% isodose (PTV90 ) were the primary endpoints. The PTV90 /V20 ratio was used as the parameter accounting for both the reduction in lung volume treated and the PTV coverage. Results: All IMRT plans, except for the three-field coplanar plans, improved the PTV90 /V20 ratio significantly compared with the optimized 3D-CRT plan. Nine coplanar IMRT beams were significantly better than five or seven coplanar IMRT beams, with an improved PTV90 /V20 ratio. Conclusion: The results of our study have shown that IMRT can reduce the dose to the lungs compared with 3D-CRT by improving the conformity of the plan.