Author of

• 20163

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  P1.14 - Radiotherapy (ID 700)

  • Event: WCLC 2017
  • Type: Poster Session with Presenters Present
  • Track: Radiotherapy
  • Presentations: 1
  • Moderators:
  • Coordinates: 10/16/2017, 09:30 - 16:00, Exhibit Hall (Hall B + C)

  • 22768

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    P1.14-001 - The Feasibility of Predicting Radiation Pneumonitis Using Lung Equivalent Uniform Dose (LEUD) in Volumetric-Modulated Arc (ID 7310)

    09:30 - 09:30  |  Author(s): Q. Deng
    • Abstract

    Background:
    The prediction of RP has become an important topic in medical field. Currently, the clinical assessment of lung injury is analyzing the dose-volume threshold based on the 3D-CRTor IMRT by controlling the percent lung volume receiving a certain amount of dose. Many literatures failed to provide an exact correlation coefficient due to data missing and nonlinear deviation in the modeling of RP prediction. Compared with the conventional radiation techniques, the low dose volume of lung is greatly enlarged especially for patients treated with VMAT or tomotherapy (TOMO). EUD is equivalent dose of inhomogeneous radiation that has the same radiobiological effect.The tissue characteristic parameter α in EUD shows the tolerance of tissue for radiation dose and the higher α, the better tolerance. Different α value are used to classify the tumor tissue, normal tissue and the serial and parallel organ in normal tissue according to “Stevens law”. The tumor tissue has a negative α value which means that in dose will lead to uncontrolled tumor. The serial organ in normal tissue has a high α value for its abnormal sensitivity to high dose. And the parallel organ has a small α for its low sensitivity.
    
    Method:
    65 patients receiving radiation therapy for lung cancer using VMAT were divided into two groups according to whether radiation pneumonitis occurred after radiation therapy. The dose-volume histogram (DVH) and its associated parameters of the patients were abstracted and analyzed by self-complied analysis program. The LEUD values of the two groups were calculated with α ranging from -50 to 50. The optimal α value was obtained when the relative LEUD difference between the two groups reached maximum.
    
    Result:
    The maximum relative LEUD difference between the group of radiation pneumonitis (GRP) and non-radiation pneumonitis (G-NRP) is obtained at α=0.5 (LEUD (GRP) =627.94 cGy, LEUD (G-NRP) = 510.23 cGy, relative LEUD difference =23.07%). The relative LEUD difference (R) reaches the maximum at α=0.5. the R tends to decrease slowly till the end of the parameter range of this study (α=50). The traditional correlation analysis of physical dose-volume threshold shows that the LEUD (α=0.5) is related to physical dose metrics including , and mean lung dose (MLD) with average person =0.929.
    
    Conclusion:
    The LEUD (α=0.5) (limited below 510 cGy) is possible to distinguish GRP from G-NRP for the thoracic tumor patients. The combination of LEUD and conventional physical dose metrics shows clinical prospective value for RP caused by non-uniform radiation.