Author of

• 13580

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  P1.04 - Poster Session/ Biology, Pathology, and Molecular Testing (ID 233)

  • Event: WCLC 2015
  • Type: Poster
  • Track: Biology, Pathology, and Molecular Testing
  • Presentations: 1
  • Moderators:
  • Coordinates: 9/07/2015, 09:30 - 17:00, Exhibit Hall (Hall B+C)

  • 13641

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    P1.04-061 - Comparison of MET Expression in Primary and Corresponding Nodal and Distant Metastases in Non-Small Cell Lung Cancer (NSCLC) (ID 2430)

    09:30 - 09:30  |  Author(s): B. Tamjid
    • Abstract

    Background:
    Hepatocyte Growth Factor and its corresponding receptor MET are potential therapeutic targets for NSCLC. In NSCLC MET is over expressed, activated and mutated and is involved in resistance to tyrosine kinase inhibitors. A high proportion of primary NSCLC cases show elevated MET expression on immunohistochemistry (IHC), however, it is not clear whether expression changes during the metastatic process. We investigated paired NSCLC tumour samples to determine whether MET receptor expression differs in the primary and its corresponding lymph node and distant metastases.
    
    Methods:
    Tissue Microarrays (TMAs) were constructed using 1mm cores of primary and metastatic matched NSCLC archival paraffin tissues in triplicate. For IHC, TMAs were stained with the SP44 clone (Ventana) and an H-score calculated based on the percentage of cells stained and their intensity with a minimum of 0 and maximum of 300. The mean of values from multiple cores was calculated. Two independent scorers assessed the tissues. Discordance was defined as an H-score difference of greater than 100 between the primary tumour and its metastasis.
    
    Results:
    61 patients with primary and matched distant metastasis were included in the main analysis with 38 (62%) male and brain the most common site of metastasis (27/61, 44%). The histology was adenocarcinoma in 26 patients, squamous cell in 21 and large cell, undifferentiated or mixed in 14. The median H-score was 100 in primary tissue and 120 in metastatic tissue. Brain secondaries showed the highest median H-score (140) compared with other metastatic sites (105). MET concordance was present in 50/61 cases (82%). MET discordance was found in 11/61 tumours including 6/26 (23%) of adenocarcinomas, 2/21 (10%) of squamous carcinomas and 3/14 (21%) of mixed or large cell tumours. Discordant elevation in metastases was present in 6/61 (10 %) and reduction in 5/61 (8%). MET FISH data was available for 54/61 of primary tissues and 60/61 of metastasis. MET was amplified only in 2/61(3%) cases, seen in both primary and secondary tissues, associated with strong positivity on IHC. An additional 75 patients had matched primary and lymph node metastasis MET IHC and FISH data available. High rate of concordance, 66/75 (88%) also was present in this nodal cohort. The median H-score was 100 in primary tissue and 117 in nodal metastatic, similar to the main primary and distant metastatic group. MET discordance between primary and nodal secondary was found only in 9/75 (12%) with discordant elevation in 4/75 (5%) and discordant reduction in 5/75 (7%). MET FISH true amplification was seen in 2 paired specimens and one primary with clonal amplification which was non-amplified in the lymph node metastasis.
    
    Conclusion:
    In this cohort of paired biopsies, increased MET expression in the primary was retained in a high proportion of distant and lymph node metastases. These data indicate that MET expression in metastases can be predicted by expression in the primary and further suggests that treatment decisions in the metastatic setting can be based on MET IHC results of archival primary or lymph node tumour.