The positive impact of cytological specimens for EGFR mutation testing in non-small cell lung cancer: a single South East Asian laboratory’s analysis of 670 cases

Authors

  • B. Pang,

    1. Cancer Science Institute, National University of Singapore, Singapore City, Singapore
    2. Department of Pathology, Yong Loo Lin School of Medicine, National University Health System, Singapore City, Singapore
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  • D. Matthias,

    1. Department of Pathology and Laboratory Medicine, University of Pittsburgh, Pittsburgh, PA, USA
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  • C. W. Ong,

    1. Cancer Science Institute, National University of Singapore, Singapore City, Singapore
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  • A. N. Dhewar,

    1. Department of Pathology, Yong Loo Lin School of Medicine, National University Health System, Singapore City, Singapore
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  • S. Gupta,

    1. Department of Pathology, Yong Loo Lin School of Medicine, National University Health System, Singapore City, Singapore
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  • G. L. Lim,

    1. Department of Pathology, Yong Loo Lin School of Medicine, National University Health System, Singapore City, Singapore
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  • M. E. Nga,

    1. Department of Pathology, Yong Loo Lin School of Medicine, National University Health System, Singapore City, Singapore
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  • J. E. Seet,

    1. Department of Pathology, Yong Loo Lin School of Medicine, National University Health System, Singapore City, Singapore
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  • A. Qasim,

    1. Department of Pathology, Yong Loo Lin School of Medicine, National University Health System, Singapore City, Singapore
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  • T. M. Chin,

    1. Cancer Science Institute, National University of Singapore, Singapore City, Singapore
    2. Department of Haematology-Oncology, Yong Loo Lin School of Medicine, National University Health System, Singapore City, Singapore
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  • R. Soo,

    1. Cancer Science Institute, National University of Singapore, Singapore City, Singapore
    2. Department of Haematology-Oncology, Yong Loo Lin School of Medicine, National University Health System, Singapore City, Singapore
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  • R. Soong,

    1. Cancer Science Institute, National University of Singapore, Singapore City, Singapore
    2. Department of Pathology, Yong Loo Lin School of Medicine, National University Health System, Singapore City, Singapore
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  • M. Salto-Tellez

    1. Cancer Science Institute, National University of Singapore, Singapore City, Singapore
    2. Centre for Cancer Research and Cell Biology, Queen’s University Belfast, UK
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Errata

This article is corrected by:

  1. Errata: Corrigendum Volume 23, Issue 6, 422, Article first published online: 22 November 2012

  • One of the authors (M.D.) was supported by the Fondation pour la recherche Nuovo-Soldati and the Research Support Foundation.

Professor M. Salto-Tellez, Centre for Cancer Research and Cell Biology, Queen’s University Belfast, 97 Lisburn Road, Belfast BT9 7BL, UK
Tel.: +44 (0) 28 9097 2760; Fax: +44 (0) 28 9097 2776; E-mail: m.salto-tellez@qub.ac.uk

Abstract

B. Pang, D. Matthias, C.W. Ong, A.N. Dhewar, S. Gupta, G.L. Lim, M.-E. Nga, J.E. Seet, A. Qasim, T.-M. Chin, R. Soo, R. Soong and M. Salto-Tellez

The positive impact of cytological specimens for EGFR mutation testing in non-small cell lung cancer: a single South East Asian laboratory’s analysis of 670 cases

Objectives:  To compare the rejection rates of non-small cell lung cancer (NSCLC) samples obtained by differing sampling methods for testing by Sanger sequencing for epidermal growth factor receptor (EGFR) mutations. To assess the association between unsatisfactory outcomes and the quantity of DNA extracted from cytological versus histological samples.

Methods:  Six hundred and seventy NSCLC samples referred to our centre from 2008 to 2010 were reviewed as a consequence of sample rejection, presence of EGFR mutations, cytological versus histological sampling methods, DNA quantity and the unsatisfactory genotyping rate.

Results:  Eighty samples were rejected for testing in similar proportions of histological and cytological samples (11.9% versus 10.9%) usually (n = 75) because the amount of cellular material was judged insufficient in small biopsies or cytology samples. The remaining 590 samples on which EGFR testing was attempted yielded 51 (8.6%) unsatisfactory test outcomes caused by failure of the polymerase chain reaction (PCR) (n = 47 cases), uninterpretable Sanger chromatograms (n = 3 cases) and insufficient DNA extracted for PCR (n = 1 case). The difference in rates of unsatisfactory outcomes between cytological samples (seven of 147 samples or 4.7%) versus tissue samples (44 of 443 samples or 9.9%) was clinically relevant but not statistically significant (Mann–Whitney test; P < 0.081). There was no association between the concentration of DNA extracted and the likelihood of an unsatisfactory analysis; which was similar in all types of sections (large and small) while 0% of 37 cytology slides were unsatisfactory.

Conclusions:  Utilizing cytology samples for EGFR testing avoids unnecessary patient re-biopsing and yields a clinically superior satisfactory rate to the overall satisfactory rate of tissue biopsies of NSCLC. The quality rather than quantity of DNA extracted may be a more important determinant of a satisfactory result.

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