M. Del Re

Real-Time PCR and Droplet Digital PCR: two techniques for detection of the JAK2(V617F) mutation in Philadelphia-negative chronic myeloproliferative neoplasms.

Philadelphia‐negative chronic myeloproliferative neoplasms (MPNs) are clonal disorders that present JAK2V617F mutation in 50–95% of cases. The main objective of this study was the comparison of two PCR methods, real‐time (qPCR) and droplet digital PCR (DD‐PCR) for detection of the JAK2V617F mutation, to assess analytic sensitivity, specificity, and feasibility of the two methods.

Pharmacogenetics of CYP2D6 and tamoxifen therapy: Light at the end of the tunnel?

The clinical usefulness of assessing the enzymatic activity of CYPD6 in patients taking tamoxifen had been longly debated. In favour of preemptive evaluation of phenotypic profile of patients is the strong pharmacologic rationale, being that the formation of endoxifen, the major and clinically most important metabolite of tamoxifen, is largely dependent on the activity of CYP2D6. This enzyme is highly polymorphic for which the activity is largely depending on genetics, but that can also be inhibited by a number of drugs, i.e. antidepressants, which are frequently used in patients with cancer. Unfortunately, the clinical trials that have been published in the last years are contradicting each other on the association between CYP2D6 and significant clinical endpoints, and for this reason CYP2D6 genotyping is at present not generally recommended. Despite this, the CYP2D6 genotyping test for tamoxifen is available in many laboratories and it may still be an appropriate test to use it in specific cases.

Synergistic interaction between PPAR ligands and salbutamol on human bronchial smooth muscle cell proliferation.

An important objective in asthma therapy is to prevent the accelerated growth of airway smooth muscle cells which leads to hyperplasia and bronchial hyperreactivity. We investigated the effect of combination of salbutamol and PPARγ agonists on growth factor‐stimulated human bronchial smooth muscle cell (BSMC) proliferation.

Prevention of fluoropyrimidine toxicity: do we still have to try our patient's luck?

1 Department of Clinical and Experimental Medicine, University of Pisa, Italy; 2 Clinical Pharmacokinetics, La Timone University Hospital, Marseille, and GPCO-Unicancer, Paris, France; 3 Department of Clinical Pharmacology, The Netherlands Cancer Institute, Amsterdam, The Netherlands; 4 Dr Margarete Fischer-Bosch-Institute of Clinical Pharmacology, Stuttgart and Department of Clinical Pharmacology, University Hospital, Tuebingen, Germany; 5 IFCC Reference center Pharmacogenetics, Department of Clinical Chemistry, Erasmus University, Rotterdam, The Netherlands; 6 Department of Clinical Chemistry, Academic Medical Center, University of Amsterdam, The Netherlands (*E-mail: romano.danesi@unipi.it)

Primary resistance to osimertinib due to SCLC transformation: Issue of T790M determination on liquid re-biopsy

OBJECTIVES EGFR T790M mutation is the most common mechanism of resistance to first-/second-generation EGFR tyrosine kinase inhibitors (TKIs) in non-small cell lung cancer (NSCLC) and could be overcome by third-generation EGFR-TKIs, such as osimertinib. Liquid biopsy, a non-invasive technique used to test the presence of the resistant mutation, may help avoiding tissue re-biopsy. However, analysing only circulating-free DNA, information about other less frequent and coexisting resistance mechanisms may remain unrevealed. MATERIALS AND METHODS All patients reported in this series participated in the ASTRIS trial, a real world treatment study testing the efficacy of osimertinib (80mg os die) in advanced T790M-positive NSCLC progressed to prior EGFR-TKI. Patients were considered eligible to osimertinib if T790M positive on tissue or plasma samples. In our patients, EGFR molecular testing on blood sample was conducted with digital droplet PCR (ddPCR). RESULTS We report our experience of five patients treated with osimertinib after T790M detection on liquid biopsy that presented a disease progression at first tumor assessment mediated by SCLC transformation, as evidenced at tissue re-biopsies. All patients showed low ratio T790M/activating mutation in the blood before osimertinib (lower than 0.03). For three patients, EGFR mutational analysis was T790M-negative when re-assessed by using a less sensitive method (therascreen®) on the same liquid biopsy sample analysed by ddPCR before osimertinib therapy. CONCLUSION Although liquid biopsy is a relevant tool to diagnose T790M presence in NSCLC patients resistant to EGFR-TKI, in case of a low ratio T790M/activating mutation, tissue biopsy should be considered to exclude the presence of SCLC transformation and/or other concomitant resistance mechanisms.

1616PLIQUID BIOPSY TO MONITOR THE EVOLUTION OF NSCLC EGFR+DURING TREATMENT WITH GEFINTINIB

ABSTRACT Aim: Resistance to EGFR tyrosine kinase inhibitors (TKI) is a clinically relevant problem that needs to be addressed by the use of appropriate technological platforms to discover the early appearance of mutations during treatment and before clinical disease progression. However, there is a lack of standardised approaches to monitor the molecular evolution of the disease under the selective pressure exerted by targeted treatments. One potential, not yet fully validated approach, is the analysis of gene mutations conferring drug resistance on cell-free circulating tumor DNA (cctDNA) released into the peripheral blood from primary tumor and metastatic sites. Periodic monitoring of the genetic evolution of the tumor, unfeasible with repeated biopsies, will greatly contribute to a better understanding and clinical management of drug resistance in cancer patients. Methods: In order to validate this approach in real-life conditions, we examined a case of acquired resistance to EGFR TKI to ascertain whether the technical platform chosen to perform this analysis is appropriate in terms of sensitivity and specificity and if it fulfills our need for molecular monitoring of the disease to improve our ability to personalise treatment. Therefore, in order to understand the cause of resistance to EGFR TKIs, a peripheral blood sample (6 ml) was drawn in a patient at first documented complete response to chemotherapy and at the three following disease progression after gefitinib. cctDNA was extracted from plasma with QIAamp Circulating Nucleic Acid Kit (Qiagen®) and molecular analysis of KRAS G12D, G12V, G12A, G12C, G12R, G12S, BRAF V600E, EGFR T790M was performed with a Digital Droplet PCR (Bio-Rad). Results: At first sampling the patient was wild type for all the tested mutations. At second sampling the patient developed the KRAS G12R and the BRAF V600E mutations. At third sampling also the the EGFR T790M was detected and the analysis confirmed the previous KRAS and BRAF mutations. Finally, the fourth sampling confirmed all three mutations. Conclusions: The liquid biopsy approach is feasible and uncovers the complexity of secondary mutations occurring in NSCLC patients treated with targeted treatments and undescores the role of the KRAS pathway in the development of resistance. Disclosure: All authors have declared no conflicts of interest.