The Detection of EGFR Mutations in Liquid Based Cytology Samples
Condition: Adenocarcinoma of Lung
MeSH terms: Adenocarcinoma; Adenocarcinoma of Lung
Study type: Observational

Summary: 
      This study will investigate whether liquid based cytology specimens are a feasible
      alternative to formalin-fixed paraffin embedded histology samples for detection of epidermal
      growth factor receptor (EGFR) mutations in lung adenocarcinoma using the Biocartis Idylla
      platform. The Biocartis Idylla is a fully automated, real-time PCR based molecular
      diagnostics system. The Idylla carries out the entire analytical process from sample to
      result.

      This study will be based in the cytology department at Royal Cornwall Hospital as part of a
      service improvement. It will use residual material from existing samples sent to the
      laboratory as part of the routine service. It will use existing material from patients
      diagnosed with lung adenocarcinoma by cytology using the current, validated procedure which
      uses formalin-fixed paraffin embedded (FFPE) samples over a 10 month period. EGFR mutation
      results obtained using the validated procedure (formalin fixed paraffin embedded) will be
      compared to those produced using liquid based cytology samples.
    

Detailed description: 
      The presence of activating epidermal growth factor receptor (EGFR) mutations identifies
      patients with lung adenocarcinoma in which EGFR tyrosine kinase inhibitors (TKI) can be a
      potential first-line treatment. The TKIs currently available are erlotinib, gefitinib and
      afatinib, which work by blocking receptor tyrosine kinase activity, thereby halting cell
      proliferation and causing cell death. Several studies have found that first-line TKI
      treatment prolongs progression free survival in comparison to standard chemotherapy, and is
      also associated with a more favourable tolerability and less adverse effects.

      Samples for EGFR mutation analysis are collected from patients by endobronchial
      ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) and bronchial brushings and
      washings. EBUS-TBNA provides a minimally invasive method for tissue sampling from
      radiologically suspicious lymph nodes in the chest using a fine-gauge needle. Samples
      obtained are collected and sent to the laboratory for processing. At present, laboratories
      rely on the use of formalin-fixed paraffin embedded (FFPE) samples for EGFR testing,
      therefore clots are produced in the laboratory using the collected tissue fragments. The
      clotted sample must then be fixed in formalin before being processed in the histology
      laboratory to produce slides for microscopic examination by the consultant pathologist. Once
      adenocarcinoma is diagnosed, FFPE samples are then sent for EGFR mutation analysis. The
      current laboratory process takes approximately 5 days.

      Liquid based cytology (LBC) specimens obtained through the same sampling procedures are also
      prepared in the laboratory and fixed using a methanol based solution (PreservCyt). Previous
      research has been carried out to determine whether LBC samples can be used instead of FFPE
      samples for the detection of EGFR mutations with favourable results. Examples of this include
      research by Zhao et al (2017), Satouchi et al (2017), De Luca et al (2017) and Malapelle et
      al (2016). A switch to the use of LBC samples for EGFR testing would remove multiple
      processing steps in the sample pathway to mutation testing. Immunocytochemistry will be
      required in the majority of cases for confirmation of adenocarcinoma. This faster pathway
      would be beneficial in cases of already confirmed adenocarcinoma for second line EGFR
      treatment testing (T790M) and in cases where the residual cytology sample, that would
      normally be discarded, can be utilised for testing, optimising the potential of the sampling.

      This study will investigate whether LBC specimens are a feasible alternative to FFPE samples
      for detection of EGFR mutations using the Biocartis Idylla platform.

      If liquid based cytology samples are found to be a feasible alternative this could result in:

        -  Quicker turnaround time of results in cases of unequivocal adenocarcinoma. This would
           provide earlier access to TKIs allowing for optimal patient management.

        -  Easier sample preparation within the laboratory

        -  Would allow for efficient use of all material acquired from the sampling procedures. For
           example additional testing could be performed on the FFPE tissue in place of EGFR
           testing which could aid in diagnosis. Increase in efficient use of material could also
           prevent repeats of the EBUS procedure on patients.

        -  Methanol has been found to be a superior fixative than formalin. Use of liquid based
           cytology samples may allow for better results from molecular testing.

        -  Would provide support to the idea that molecular testing for other cancers may be able
           to be carried out on liquid based cytology samples for example BRAF mutation testing for
           melanoma. Also provides support of the use of other liquid samples for molecular testing
           such as blood samples which could be tested for circulating tumour cells (less invasive
           sampling).
    

Observational model: Case-Only
Time perspective: Retrospective
Sampling method: Non-Probability Sample
Study population: 
        Samples from patients who have been diagnosed with lung adenocarcinoma by the cytology
        laboratory at Royal Cornwall Hospital Treliske using the current validated method on
        formalin-fixed paraffin embedded samples.