Author of

• 11866

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  P2.18 - Poster Session 2 - Pathology (ID 176)

  • Event: WCLC 2013
  • Type: Poster Session
  • Track: Pathology
  • Presentations: 1
  • Moderators:
  • Coordinates: 10/29/2013, 09:30 - 16:30, Exhibit Hall, Ground Level

  • 11875

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    P2.18-009 - Mutation Testing in Non-Small Cell Lung Cancer - Suitability of Small Biopsy and Cytology Specimens (ID 1750)

    09:30 - 09:30  |  Author(s): S. Wang
    • Abstract

    Background
    Patients with non-small cell lung cancer (NSCLC) harboring sensitizing mutations in epidermal growth factor receptor (EGFR) benefit from treatment with EGFR tyrosine kinase inhibitors. As most patients with NSCLC present with advanced-stage disease and are not candidates for surgical resection, somatic mutation testing is often performed on small biopsy and cytology specimens. Compared to resection specimens, the suitability of these specimens is not well established. We aimed to explore the suitability of small biopsy and cytology specimens for mutation testing in NSCLC.

    Methods
    We undertook a retrospective review of NSCLC mutation testing cases performed at Royal Prince Alfred Hospital, Sydney, from March 2012 to May 2013. Mutation testing was requested by the treating physician. DNA was extracted from formalin-fixed, paraffin embedded tissue and a multiplex PCR assay (OncoCarta Panel v1.0) used to identify mutations in 19 oncogenes including EGFR, KRAS, and BRAF. The results were analyzed on the Sequenom MassArray platform. Fragment analysis was also undertaken to assess for exon 19 deletions.

    Results
    Mutation testing was undertaken on 151 NSCLC specimens, including 44 (29.1%) resection specimens (27 lung resection specimens and 17 metastatic site resections), 67 (44.4%) small biopsy specimens, and 40 (26.5%) cytology specimens. Overall, EGFR mutations were detected in 32/151 (21.2%) cases, KRAS mutations in 29/151 (19.2%) cases, and BRAF mutations in 3/151 (2%) cases. Mutations were detected in 25/44 (56.8%) resection specimens, principally lung resection specimens (19/27, 70.4%), 26/67 (38.8%) small biopsies and 13/40 (32.5%) cytology specimens. The mutation rate was significantly lower in small biopsies (p=0.006) and cytology specimens (p=0.002), compared to lung resection specimens. Specifically, EGFR mutations were identified in 13/44 (29.5%) resection specimens, again mainly in lung resection specimens (10/27, 37%), 9/67 (13.4%) small biopsies and 10/40 (25%) cytology specimens. Compared to lung resection specimens, the proportion of EGFR mutation positive cases was significantly lower in small biopsy (p=0.01), but not in cytology specimens (p=0.29). One paired cytology and lung resection specimen from a single patient was available and both specimens confirmed the presence of an L858R EGFR mutation.

    Conclusion
    Mutations, including EGFR mutations, were most frequently detected in lung resection specimens. Compared to lung resection specimens, the EGFR mutation rate was significantly lower in small biopsy, but not in cytology specimens. This suggests that cytology specimens are more likely to be adequate for mutation testing than small biopsies such as core and bronchial biopsies. However, we cannot exclude bias in this study from differing referral patterns which may affect these results. Careful assessment of DNA quality and quantity is important for all specimens, particularly small biopsy specimens, to reduce the risk of false positive or negative results.