Author of

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  P19 - Locoregional and Oligometastatic Disease - Oligometastatic Disease (ID 129)

  • Event: WCLC 2020
  • Type: Posters
  • Track: Locoregional and Oligometastatic Disease
  • Presentations: 1
  • Moderators:
  • Coordinates: 1/28/2021, 00:00 - 00:00, ePoster Hall

  • 35162

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    P19.01 - Local Ablative Radiotherapy on Oligo-Progression while Continued on EGFR-TKI in Advanced NSCLC Patients: A Longer Cohort (ID 1505)

    00:00 - 00:00  |  Presenting Author(s): Florence Siu Ting Mok
    • Abstract
    • Slides

    Introduction
    

    Continuation of Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitors (EGFR-TKI) in advanced Non-small cell Lung cancer (NSCLC) patients harboring sensitive mutation (Exon 19 deletion /Exon 21 L858R mutation) upon first progression according to RECIST criteria can prolong the use of EGFR-TKI for more than 3 months till change of therapy. Local ablative radiotherapy (LAR) on oligo-progression is widely used but actual benefit is yet to be quantified.

    Methods
    

    Health records of patients given LAR from 2012-2019 in a single centre were reviewed. Patients with stage IV NSCLC harboring epidermal growth factor receptor (EGFR) activating mutations having <5 sites of oligo-progression while on EGFR TKI and given LAR with 1-8 fractions were included. Demographics, site of oligo-progression, radiotherapy sites and dose/fractionation schedules were captured. Duration from start of TKI to oligo-progression was defined as PFS1. The primary endpoint was progression free survival from LAR to further progression that led to stop of EGFR TKI (PFS2). The secondary endpoint was overall survival from LAR. Potential factors affecting PFS2 and OS were analyzed with Cox regression model.

    Results
    

    There were total 55 eligible patients. The mean age at delivery of LAR was 62.7 (36-88) years. Majority (89%) had sensitive mutations (Exon 19 deletion and exon 21 L858R mutation). The median PFS1 was 17.2 months (95% CI 11.4 to 23.0). Total number of lesions treated were 75, including lung (n=45), bone (n=15), cervical lymph node (n=1), adrenal (n=1) and brain (n=13). The mean radiation doses with biological equivalent dose with α/β= 10 (BED10) were: lung: 112.2Gy (100.0-151.2Gy); bone: 47.8 Gy (41.6- 100Gy); brain: 61.7Gy (37.5-70.4Gy). The patient with metastatic lymph node was given 60Gy in 8 fractions (BED10= 105Gy) and with adrenal metastasis was given 40Gy in 5 fractions (BED 10= 72Gy). The mean time from diagnosis of oligo-progression to LAR was 2.2 months (0.6 to 4.6 months). No significant toxicities were reported. The median follow-up time was 13.3 months (1.5-51.6 months).
    
    The median PFS1 was 17.2 months (95% CI 11.4 to 23.0). Median PFS2 was 6.9 months (95% CI 3.1- 10.7 months). The 1-year and 2-year local control rate were 86% and 78%. The 1-year and 2-year distant control rates were 29% and 16%. The median OS from LAR was 25.1 months (95% CI 10.0-40.10 months). On multivariable analysis, it was found that patients with EGFR mutation type (exon 19 deletion or L858R mutation) had superior PFS2 (HR 0.11 95% CI 0.03-0.41, p =0.001) and OS (HR 0.099 95 CI 0.010-0.961, p=0046) compared with other less common mutations, while longer time to treatment (>70 days) and more lines of TKI before LAR negatively affected PFS2 (p=0.046; 0.004). Age, sex, smoking status, CNS involvement, number of radiation sites, PFS1 and treatment dose did not affect PFS2 and OS with statistical significance.

    Conclusion
    

    LAR is a safe and convenient modality in treatment of oligo-progressive disease for patients with EGFR mutations positive NSCLC. Patients with EGFR exon 19 deletion or Exon 21 L858R mutation, shorter time from diagnosis to treatment, and less prior lines of EGFR-TKI may benefit more from LAR.

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