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P.M. Das
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P1.02 - Poster Session with Presenters Present (ID 454)
- Event: WCLC 2016
- Type: Poster Presenters Present
- Track: Biology/Pathology
- Presentations: 1
- Moderators:
- Coordinates: 12/05/2016, 14:30 - 15:45, Hall B (Poster Area)
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P1.02-008 - 2-Year Single Institution Experience with EGFR Plasma Testing in Advanced NSCLC (ID 4281)
14:30 - 14:30 | Author(s): P.M. Das
- Abstract
Background:
Lung adenocarcinoma patients in advanced stage of disease that harbor EGFR sensitizing mutations are eligible for treatment with tyrosine kinase inhibitors (TKI) due to a high likelihood of response. Most patients will ultimately develop resistance at disease progression. The T790M mutation is a dominant resistance mechanism to TKI. EGFR plasma testing enables non-invasive monitoring and detection of T790M. We followed patients with EGFR sensitizing mutations by measuring EGFR mutations in plasma during TKI treatment.
Methods:
We analyzed patients who were diagnosed lung adenocarcinoma stage IV, detected EGFR sensitizing mutations in tumor tissue samples and treated with TKI at University Clinic Golnik. We collected baseline plasma samples prior to TKI treatment and consecutive plasma samples at different time intervals after initiation of therapy. At the beginning, two separate tests, cobas® EGFR Mutation Test for tissue (CE-IVD) and plasma (under development) were used, and since October 2015 one test for tissue and plasma, cobas® EGFR Mutation Test v2 (Roche, Pleasanton, CA, USA) is used. Detected EGFR mutations in plasma samples were expressed as semi-quantitative index (SQI) which reflects a proportion of mutated versus wild-type copies of the EGFR gene.
Results:
During 2-year period we collected 414 peripheral blood samples from 63 patients and performed 619 EGFR plasma tests. There are 25 patients with baseline and serial follow-up EGFR plasma tests, 16 patients with only serial follow-up EGFR tests since they started with TKI treatment before EGFR plasma testing was available, 5 patients are included in adjuvant setting, and 17 patients had no monitoring due to various reasons. Maximum number of EGFR plasma tests done per patient was 27 at 20 time-points. When introducing EGFR plasma testing, we prepared two aliquots of plasma out of 10 ml blood sample in EDTA-tubes and run test for both aliquots. Results of reproducibility study showed 95% concordance rate between both aliquots and thus we modified protocol to run the second aliquot only if the first one was negative. At disease progression, reappearance of EGFR sensitizing mutations with increasing SQI levels was detected. In 14 patients who progressed we detected T790M mutation, in 10 of them during monitoring TKI treatment. We also observed daily variation in EGFR mutation levels in the plasma.
Conclusion:
These data support the value of EGFR plasma testing to monitor the patient`s response to TKI and detect T790M resistance mutation prior to clinical progression in a routine clinical setting.
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P3.02b - Poster Session with Presenters Present (ID 494)
- Event: WCLC 2016
- Type: Poster Presenters Present
- Track: Advanced NSCLC
- Presentations: 1
- Moderators:
- Coordinates: 12/07/2016, 14:30 - 15:45, Hall B (Poster Area)
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P3.02b-043 - Inter-Laboratory Comparison of the Roche Cobas EGFR Mutation Test v2 in Plasma (ID 4277)
14:30 - 14:30 | Author(s): P.M. Das
- Abstract
Background:
Molecular testing of the EGFR gene is required to predict therapeutic response in non-small cell lung cancer (NSCLC). Although routinely performed, analysis of tumor tissue is subject to limitations. Analysis of circulating tumor DNA (ctDNA) in blood plasma may overcome these barriers, and techniques to detect and quantify variants in ctDNA are emerging. However, several key elements like sensitivity and specificity still need to be addressed. This study evaluates the inter-laboratory performance and reproducibility of the cobas[®] EGFR Mutation Test v2 for the detection of common EGFR variants in plasma.
Methods:
Fourteen laboratories from ten European countries received two identical panels of 27 single-blinded plasma members (Roche Molecular Systems, CA, USA). Samples were wild-type or spiked with plasmid DNA containing seven common EGFR variants at six predefined concentrations from 50-5000 target copies per mL (cp/mL). ctDNA was extracted by the Roche cobas[®] cfDNA Sample Preparation kit, followed by duplicate analysis with the Roche cobas[®] EGFR Mutation Test v2 kit. All sites received hands-on training and two obligatory proficiency samples to assure operator qualification. Statistical analyses were performed with SAS 9.4 (SAS Institute Inc., NC, USA).
Results:
In total, 0.8% (12/1512) and 0.2% (3/1512) of runs were excluded due to protocol deviations or technical failures respectively. The sensitivity was lowest for the c.2156G>C;p.(G719A) variant with values of 80.4%, 69.6% and 89.1% at 50, 100 and 250 cp/mL respectively. Besides 88.7% for the c.2573T>G;p.(L858R) variant at 50 cp/mL, sensitivities for all other variants or concentrations varied between 96.3-100.0% and improved for increasing cp/mL. Specificities were all 98.8%-100.0%. Coefficients of variation (CV) indicate good intra-laboratory repeatability and inter-laboratory reproducibility, but increased for decreasing concentrations. Highest CV’s were reported for c.2156G>C;p.(G719A), c.2307_2308ins;Ex20Ins, and c.2582T>A;p.(L861Q) at 50 cp/mL. Prediction models reveal a significant correlation between the observed semi-quantitative index values (SQI) and copy numbers in plasma for all variants. A systematic over- and underestimation was observed for four different variants at 1000 and 5000 cp/mL respectively.
Conclusion:
This study demonstrates an overall robust performance of the cobas® EGFR Mutation Test v2 in plasma, suggesting a valuable and convenient addition to molecular tumor analysis in NSCLC. Repeated tests are advisable in case of low SQI values to reduce the average variation. Prediction models could be applied by future users to estimate the plasma tumor load from the observed SQI value, taking into account the possibility of systematic errors for high target copies.
