Author of

• 11389

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  O10 - Stereotactic Ablative Body Radiotherapy (ID 104)

  • Event: WCLC 2013
  • Type: Oral Abstract Session
  • Track: Radiation Oncology + Radiotherapy
  • Presentations: 1
  • Moderators:H. Onishi, J.Y. Chang
  • Coordinates: 10/28/2013, 16:15 - 17:45, Parkside 110 A+B, Level 1

  • 11394

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    O10.05 - Blinded assessment of radiological changes after stereotactic ablative radiotherapy for early-stage lung cancer: local recurrences versus fibrosis. (ID 1416)

    16:15 - 17:45  |  Author(s): B. Slotman
    • Abstract
    • Presentation
    • Slides

    Background
    Stereotactic ablative radiotherapy (SABR) is now a guideline-recommended treatment for early-stage lung cancer (ES-NSCLC), achieving 5-year local control rates of approximately 10%. The timely detection of local recurrence (LR) and early salvage following SABR is impaired by fibrotic changes, which occur commonly. Seven high-risk CT features (HRFs) that suggest LR include; enlarging opacity, cranio-caudal growth, sequential enlarging opacity, enlarging opacity after 12 months, bulging margin, loss of linear margin and loss of air bronchograms. We validated these, performing blinded clinician assessment in patients with and without LR.

    Methods
    ES-NSCLC patients treated with SABR, who developed pathology-proven LR (n=12), were matched 1:2 to patients without clinical LR (n=24), based on tumor location, SABR fractionation, PTV size and follow-up duration. Three radiation oncologists assessed serial follow-up CT images for HRFs, while blinded to outcomes. The sensitivity and specificity of HRFs and combinations of these were determined.

    Results
    The median follow-up was 24 months (range 6-67) and both cohorts were well matched. All HRFs were significantly associated with LR (p≤0.002), Table 1. The best individual predictor of LR was opacity enlargement after 12 months (100% sensitivity, 83% specificity), however this was detected slowest, at a median 22 months. The earliest HRF detected was cranio-caudal growth detected at a median 13 months. The HRFs enlarging opacity and cranio-caudal growth were each detected at least 3 months prior to the actual diagnosis of LR 42% of the time. The odds of LR increased 4-fold for each additional HRF detected (p<0.001). The sensitivity and specificity of detecting multiple HRFs is shown in Table 2, with ≥3 HRFs being the best predictor of LR (sensitivity 92%, specificity 92%). Figure 1 Figure 2

    Conclusion
    LR following SABR can be accurately predicted by the presence of HRFs on surveillance CT scans. This approach may reduce unnecessary confirmatory procedures, and facilitate earlier salvage treatment.

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