Comparison of Intensity-Modulated Radiation Therapy (IMRT) in the Treatment of Inoperable Non-small Cell Lung Cancer

Objective: To systematically evaluate intensity-modulated radiation therapy(IMRT) used to treat non-small cell lung cancer, investigate the conformity index (CI), heterogeneity index (HI), the dose to organs at risk(OARs), and evaluate the difference in the IMRT plans using five, seven, and nine beams. Methods: A retrospective treatment planning study was performed to compare IMRT plans for 22 patients with StageⅠto Ⅲ inoperable NSCLC. One target volume was predefined: PTV, which was given 66 Gy. Three plans were designed for each patient: 5, 7 and 9 beams IMRT plans. The dosimetric distribution, normal tissue complication probability(NTCP), the dose of organs at risk were calculated. Results: Under the same prescription dose, CI of 5, 7 and 9 beams IMRT plan were 0.68, 0.70, 0.70, HI of 5, 7 and 9 beams IMRT plans were 1.18, 1.18, 1.19. The total lung volume receiving radiation 20 Gy (V20) were 16.95%, 16.82%, 16.73%, NTCP were 2.26%, 2.43%, 2.42%. The total esophageal volume receiving radiation 50 Gy (V50) were 6.68%, 6.82%, 6.59%, NTCP were 5.07%, 4.74%, 4.6%. The dose of 1% spinal cord volume were 3424 cGy, 3726 cGy, 3675 cGy, NTCP were 0.2%, 0.25%, 0.18%. Conclusions: For treatment of non-small-cell lung cancer, IMRT plans may result in a desirable dose distribution. Five beams IMRT plan can be accepted by clinical.