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    P1.13 - Targeted Therapy (Not CME Accredited Session) (ID 945)

    • Event: WCLC 2018
    • Type: Poster Viewing in the Exhibit Hall
    • Track:
    • Presentations: 1
    • Moderators:
    • Coordinates: 9/24/2018, 16:45 - 18:00, Exhibit Hall
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      P1.13-23 - TP53 Mutations as Mechanisms of Primary and Acquired Resistance to Tyrosine Kinase Inhibitors in Patients With EGFR-Mutated NSCLC  (ID 13954)

      16:45 - 18:00  |  Author(s): Vienna Ludovini

      • Abstract
      • Slides

      Background

      Around 80% of patients with non-small cell lung cancer (NSCLC) harboring epidermal growth factor receptor (EGFR) mutations usually respond to tyrosine kinase inhibitors (TKIs). We previously demonstrated that TP53 mutations are associated with primary resistance to TKIs in patients with EGFR-mutated lung adenocarcinoma (ADC) treated with a first-line TKI. In the present study we investigated whether TP53 mutations are modulated by TKIs, evaluating its status before and after TKI treatment.

      a9ded1e5ce5d75814730bb4caaf49419 Method

      Thirty-five patients with EGFR-mutated lung ADC treated with a first-line TKI and who subsequently underwent re-biopsy after disease progression were considered. Tumor tissue was available for evaluation before and after TKI treatment for all patients. EGFR and TP53 mutation analyses were performed by Sanger Sequencing or Next Generation Sequencing methods. The different mutations were evaluated in relation to disease control rate (DCR) [complete response (CR), partial response (PR) or stable disease (SD)] and objective response rate (ORR) (CR, PR).

      4c3880bb027f159e801041b1021e88e8 Result

      Of the 35 patients, 14 (40%) showed a TP53 mutation, 12 in exons 5-8 (5 in exon 5, 2 in exon 6, 2 in exon 7 and 3 in exon 8) and 2 in other exons (1 in exon 2 and 1 in exon 4) of the gene. The group was treated with a first-line TKI and data on response and follow-up were available for 30 patients. Of these, 11 were treated with gefitinib, 11 with erlotinib, 6 with afatinib and 2 with dacomitinib. Overall DCR and ORR were 90% and 77%, respectively. With regard to TP53 mutations, DCR and ORR were 94% and 83%, respectively, in TP53 wt patients, and 83% and 66% in TP53 mutated cases. All 30 patients underwent re-biopsy at progression and 20 (67%) showed T790M mutation in tumor tissue. Of the 10 T790M-negative patients, 5 (50%) had a TP53 mutation which was not present at baseline in 2 cases. Among the patients who were TP53 wild type at baseline, 4 (22%) showed a mutation at disease progression. Data on progression free survival and overall survival are currently being evaluated.

      8eea62084ca7e541d918e823422bd82e Conclusion

      TP53 mutations were associated with a lower response to TKIs in EGFR-mutated patients and may have been acquired during TKI treatment, independently of the T790M mutation.

      6f8b794f3246b0c1e1780bb4d4d5dc53

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