Author of

• 10692

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  P1.08 - Poster Session 1 - Radiotherapy (ID 195)

  • Event: WCLC 2013
  • Type: Poster Session
  • Track: Radiation Oncology + Radiotherapy
  • Presentations: 1
  • Moderators:
  • Coordinates: 10/28/2013, 09:30 - 16:30, Exhibit Hall, Ground Level

  • 10715

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    P1.08-023 - How to Minimize the Uncertainties of Internal Target Volume in 4DCT Scans for Stereotactic Body Radiation Therapy of Early Stage Non-small Cell Lung Cancer (ID 2832)

    09:30 - 09:30  |  Author(s): X. Bai
    • Abstract

    Background
    Precise definition of the target volume is one of crucial factors in the management of early stage non-small cell lung cancer (NSCLC) with stereotactic body radiation therapy (SBRT). Recent studies have shown that individualized planning margins are required to account for the variability and unpredictability of lung tumor motion. The spatial and temporal information on tumor motion can be derived with respiration-correlated 4DCT scans. In this study, we investigated how these uncertainties may be individually minimized for SBRT of NSCLC.

    Methods
    Twelve patients with early stage NSCLC who were undergoing SBRT were imaged with free-breathing 3-dimensional computed tomography (3DCT) and 10-phase 4-dimensional CT (4DCT) for delineating gross tumor volume (GTV)3D and ITV10Phase (ITV2). The maximum intensity projection (MIP) CT was also calculated from 10-phase 4DCT for contouring ITVMIP (ITV1). Then, ITVCOMB (ITV3), and ITV10Phase+GTV3D (ITV4), were generated by combining ITVMIP, ITV0% phase and ITV50% phase, ITV10phase and GTV3D, respectively. All 5 volumes (GTV3D and ITV1 to ITV4) were delineated in the same lung window by the same radiation oncologist.

    Results
    The mean (range) tumor motion (RSI, RAP, RML, and R3D ) were 6 mm (2-11 mm), 3 mm (1-4 mm), 4 mm (0-6 mm), and 7 mm (3-12 mm), respectively. The trend of volume variation was GTV3D < ITV1 < ITV2 < ITV3 ≈ ITV4 . The means ± SDs of these volumes were 10 ± 7 cc, 10 ±8 cc, 12 ± 7 cc, 11 ± 8 cc, and 12 ± 8 cc, respectively. All comparisons between the target volumes showed statistical significance ( P<0.05), except for ITV3 and ITV4 (P= 0.732). The volume of the combining ITVMIP, ITV0% phase and ITV50% phase was closed to ITV10phase plus GTV3D.

    Conclusion
    Uncertainties in individualized ITVs for SBRT of early stage NSCLC could effectively be minimized by combining information from free-breathing 3DCT and 10-phase 4DCT. If these images cannot be efficiently contoured, a combination of ITVMIP, ITV0% phase and ITV50% phase could be an effective alternative.