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

  • 10694

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    P1.08-002 - Relation of tumor response to radiation dose distribution in locally advanced non-small cell lung cancer undergoing concurrent chemoradiotherapy (ID 201)

    09:30 - 09:30  |  Author(s): S. Lee
    • Abstract

    Background
    To determine whether the quality of radiation dose distribution is associated with the tumor response of advanced non-small cell lung cancer (NSCLC) undergoing concurrent chemoradiotherapy (CCRT).

    Methods
    Thirty one patients with stage IIIA/IIIB NSCLC underwent CCRT with a median dose of 63 Gy (range 40-66 Gy). The chemotherapy combined taxene and alkylating agents. On our actual plans, we drew the planning target volume (PTV) including the electric nodes and tried to make a plan to cover the PTV with at least 95% of prescribed dose. The following CT simulation was done when a cumulative dose was about 36 Gy and the cone-down was undergone at about 40 Gy only including the primary tumor and the bulky nodes. For this retrospective study, each PTV of primary tumor (n=30) and lymph nodes (n=36) was separately re-defined with even margins from gross target volume (GTV) to reduce the variation of target delineation, and the actual plan overlaid the re-defined PTV. For the measurement of tumor response rate during CCRT (RR(mid)) and after CCRT (RR(end)), the GTV on initial simulation was compared with the GTV on following CT simulation and following CT scan after 2 months from end of CCRT, respectively. The relations between the RR(mid), RR(end), dose distribution parameters (D~95~, V~95~, mean tumor dose (MTD) and homogeneity index (HI)), total dose and tumor volume were evaluated by bivariate correlation analysis.

    Results
    Median overall survival was 15.5 months and 2-year survival 42.3%. For primary tumors and lymph nodes, the dose distribution parameters were favorable (Table). For primary tumors, the relation between dose distribution parameters and tumor response was not significant. The RR(end) was correlated with the GTV on following CT simulation (γ=0.627, p<0.001) and the RR(mid) (γ=0.541, p=0.003). For lymph nodes, the RR(mid) was correlated with the mean tumor dose (γ=0.356, p=0.033).

    Mean/SD (%)	D~95~	V~95~	MTD	HI
    Tumor Node	97.4/2.5 96.6/6.7	99.7/5.4 100.0/23.5	100.3/1.0 98.6/3.1	2.9/1.4 2.2/1.7

    Conclusion
    The quality of radiation dose distribution minimally affected the tumor response. Based on the marked association between the RR(mid) and RR(end), further studies of tumor intrinsic factors related to radiation sensitivity will be rewarding.