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  MO23 - Radiotherapy II: Lung Toxicity, Target Definition and Quality Assurance (ID 107)

  • Event: WCLC 2013
  • Type: Mini Oral Abstract Session
  • Track: Radiation Oncology + Radiotherapy
  • Presentations: 1
  • Moderators:M.M. Tin, F. Macbeth
  • Coordinates: 10/30/2013, 10:30 - 12:00, Bayside 204 A+B, Level 2

  • 12968

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    MO23.02 - Quantification of radiation-induced lung damage with CT scans: The possible benefit for radiogenomics (ID 254)

    10:35 - 10:40  |  Author(s): G. Defraene
    • Abstract
    • Presentation
    • Slides

    Background
    Radiation-induced lung damage (RILD) is an important problem. Although physical parameters such as the mean lung dose are used in clinical practice, they are not suited for individualised radiotherapy. As radiosensitivity varies between patients, genetic correlations have been investigated, which appear to be difficult to repeat in validation studies. This may be due, in part, to differences in methods for measuring RILD across studies. Objective, quantitative measurements of RILD on a continuous instead of on an ordinal, semi-quantitative, semi-subjective scale, are needed.

    Methods
    Hounsfield Unit (HU) changes before vs. 3 months post-radiotherapy were correlated per voxel with the radiotherapy dose. Deformable registration was used to register pre and post CT scans and the density increase was quantified for various dose bins. The dose-response curve for increased HU was quantified using the slope of a linear regression (HU/Gy). The end-point for the toxicity analysis was dyspnoea ≥ grade 2.

    Results
    95 lung cancer patients were studied. Radiation dose was linearly correlated with the change in HU (mean R[2]=0.74 ± 0.28). No differences in HU/Gy between groups treated with stereotactic radiotherapy, conventional radiotherapy alone, sequential or concurrent chemo-radiotherapy were observed. In the whole patient group, 33/95 (34.7 %) had dyspnoea ≥ G2. Of the 48 patients with a HU/Gy below the median, 16 (33.3 %) developed dyspnoea ≥ G2, while in the 47 patients with a HU/Gy above the median, 17 (36.1 %) had dyspnoea ≥ G2 (not significant). Individual patients showed a nearly 21-fold difference in radiosensitivity, with HU/Gy ranging from 0 to 10 HU/Gy. Figure 1

    Conclusion
    HU changes identify objectively the whole range of individual radiosensitivity on a continuous, quantitative scale. CT density changes may allow more robust and accurate radiogenomics studies.

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