130P - EGFR plasma testing in routine practice by real-time PCR in lung cancer patients: experience of 262 patients

Date 11 September 2017
Event ESMO 2017 Congress
Session Poster display session
Topics Cancer in Adolescents
Biomarkers
Lung and other Thoracic Tumours
Presenter Philippe Taniere
Citation Annals of Oncology (2017) 28 (suppl_5): v22-v42. 10.1093/annonc/mdx363
Authors P. Taniere1, P. Taniere2, M. Smith3, B. O'Sullivan4, F. Hughes4, T. Mullis1, N. Trim1, S. Baijal5, Q. Ghafoor6, G. Middleton7
  • 1Molecular Pathology Diagnostic Service, Queen Elizabeth Hospital Birmingham, b152wb - birmingham/GB
  • 2Molecular Pathology Diagnostic Service, Queen Elizabeth Hospital Birmingham, b152wb - Birningham/GB
  • 3Molecular Pathology Diagnostic Service, Queen Elizabeth Hospital Birmingham, B15 2WB - Birmingham/GB
  • 4Molecular Pathology Diagnostic Service, Queen Elizabeth Hospital Birmingham, b152wb - Birmingham/GB
  • 5Oncology, Heartlands Hospital-Heart of England NHS Foundation Trust, B9 5SS - Birmingham/GB
  • 6Oncology, New Queen Elizabeth Hospital Birmingham, B15 2GW - Birmingham/GB
  • 7Oncology, Queen Elizabeth Hospital Birmingham, b152wb - Birmingham/GB

Abstract

Background

EGFR mutation testing in lung cancer prior to tyrosine kinase inhibitor (TKI) therapy can be performed in tissue or plasma in practice. Both techniques are complementary; however, plasma testing can represent a surrogate for re-sampling a tumour in patients progressing under TKI prior to prescription of osimertinib, but clinical sensitivity of the test remains to be determined. We present our twelve-month experience of integrating EGFR plasma testing into our service with a series of 262 cases. We currently receive over 50 cases per month.

Methods

EGFR mutation testing for both tissue and plasma is performed using cobas EGFR Mutation Test v2, which covers 29 deletions in exon 19, T790M, L858R, G719X, S768I, L861Q and 5 insertions in exon 20. For plasma testing, DNA is extracted using the cobas cfDNA sample preparation kit. All samples were submitted in Paxgene ccfDNA tubes.

Results

Of the 262 cases submitted for testing, five failed (1.9%). 123 mutations, including 42 T790M, were detected. Turnaround time was two days. Clinical sensitivity is very difficult to assess because of the uncertainty of the presence of circulating tumour DNA at all. All types of primary mutation were detected: 70 exon 19 deletions, 42 L858R, 2 G719X, 5 L861Q, 3 combined S768I and G719X, and 1 singlet T790M. Clinical details were not available for all patients. A sensitising mutation was found in 51 of 92 patients (55.5%) under TKI therapy, where this was indicated on the request form; among these, an associated T790M mutation was found in 19 (37%) of patients. Several patients underwent multiple tests while they received TKI therapy; in two patients, the secondary mutation was detected prior to clinical progression.

Conclusions

We show here that EGFR plasma testing is perfectly suitable for clinical practice; it is highly specific and cost-effective due to rapid turnaround times, but the low sensitivity renders it complementary to tissue testing rather than a true surrogate.

Clinical trial identification

N/A

Legal entity responsible for the study

N/A

Funding

None

Disclosure

All authors have declared no conflicts of interest.