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Clive Morris



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    FP07 - Pathology (ID 109)

    • Event: WCLC 2020
    • Type: Posters (Featured)
    • Track: Pathology, Molecular Pathology and Diagnostic Biomarkers
    • Presentations: 1
    • Moderators:
    • Coordinates: 1/28/2021, 00:00 - 00:00, ePoster Hall
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      FP07.11 - Circulating Tumor DNA (ctDNA) Clearance as a Biomarker in Patients With Locally Advanced NSCLC Following Chemoradiation (ID 1432)

      00:00 - 00:00  |  Author(s): Clive Morris

      • Abstract
      • Presentation
      • Slides

      Introduction

      Circulating tumor DNA (ctDNA) testing has the potential to identify patients at high risk for recurrence following completion of concurrent chemoradiation (CRT) for locally advanced non-small cell lung cancer (LANSCLC). The objective of this analysis is to examine the feasibility of ctDNA testing on a commercially available focused gene panel to predict outcomes in patients with LANSCLC.

      Methods

      A total of 43 patients were prospectively enrolled between 09/2017 and 10/2019. Plasma for ctDNA testing was collected at the time of CRT initiation (D1), CRT completion (V1), quarterly follow up appointments for 12 months (FU1, 2, 3 and 4 respectively) after CRT completion, and at the time of relapse (R). ctDNA analysis was performed using InVisionFirst®-Lung, to detect the presence of SNVs, indels and CNAs in 37 cancer-related genes. ctDNA clearance was defined as the absence of D1 variants at V1. Patients without detectable D1 variants or in whom V1 samples were not collected were excluded from this analysis.

      Results

      Nineteen of 43 patients (44%) had detectable variants at D1. In this cohort of 19 patients, the median age at diagnosis was 65 years (range 43 - 82), with the majority of patients being smokers (16/19, 84%). The stage distribution was as follows: IIA (5%), IIIA (37%), IIIB (52%) and IIIC (5%). Nine patients (47%) had squamous cell carcinoma, 7 (37%) had adenocarcinoma, and 3 (16%) had poorly differentiated or NSCLC NOS. A median of 2 mutations per sample (range 1 - 5) were detected with a median of mean allelic frequency (AF) of 0.53 (range 0.05 - 16.28) at D1. Mutations in TP53 were the most commonly detected (17/19, 89%) at D1, followed by mutations in PIK3CA (5/19, 26%), CDKN2A (4/19, 21%), and EGFR (3/19, 16%). Two patients died from non-cancer related causes before FU1 and were excluded from further analysis (1 cleared ctDNA, another did not). All (3/3) patients who did not clear ctDNA had tumor relapse with a median time to relapse of 74 days (30-238), while 50% (7/14) of those who cleared ctDNA have not relapsed after a median follow-up of 469 days (range 130-710). Median time to relapse in patients who cleared ctDNA was 217 days (range 53-587 days).

      Conclusion

      Our results demonstrate that it is feasible to employ ctDNA testing to identify LANSCLC patients who are at high risk for disease recurrence following CRT. This finding requires validation in future studies.

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