OSNA testing for lymph node staging in colorectal cancer
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  • Published on:
    Authors' reply
    • Richard Colling, Clinical Lecturer in Histopathology University of Oxford
    • Other Contributors:
      • Trevor Yeung, Clinical Lecturer
      • Roel Hompes, Consultant Colorectal Surgeon
      • Rebecca Krauss, Colorectal Surgeon
      • Ronan Cahil, Professor of Surgery
      • Neil Mortensen, Professor of Colorectal Surgery
      • Lai Mun Wang, Consultant Pathologist

    We were pleased to read the correspondence ‘Stage II patients can benefit from OSNA molecular lymph node staging’ from Cuatrecasas et al. and grateful for the authors’ interest and comments. Our study with one-step nucleic acid amplification (OSNA) for patients with colorectal cancer (CRC) primarily aimed to evaluate the accuracy of the test as compared with the standard care approach of a single H&E microscopic examination. We hoped to share with readers our experiences of working with this technology and highlight the challenges other centres will need to consider before introducing the service.[1]
    While we acknowledged the concern raised by Cuatrecasas et al. that our study cohort of 19 patients is small, we emphasise that we tested 82 lymph nodes with OSNA and feel our results show a fair indication of the concordance of the assay with routine histology. It is also important to point out that initially more patients were recruited for the study but several specimens had to be excluded due to faecal contamination, sealed perforation or macroscopic serosal (T4) disease – all of which could arguably lead to false positive results by OSNA. The significance of our data is that to our knowledge this was the first time OSNA had been fairly compared with routine histology rather than intensive work-up of multiple levels, immunohistochemistry (IHC) and conventional molecular methodologies. We agree that there is insufficient convincing evidence that intensive interrog...

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    Conflict of Interest:
    None declared.
  • Published on:
    Stage II patients can benefit from OSNA molecular lymph node staging
    • Miriam Cuatrecasas, Gastrointestinal Pathologist Hospital Clinic, Barcelona. Spain
    • Other Contributors:
      • Sherley Diaz, Pathologist
      • Iban Aldecoa, Pathologist

    Dear Sirs,

    We have read with interest and concern the correspondence letter published in the July issue of your journal “OSNA testing for lymph node staging in colorectal cancer”.
    Although the authors state on the letter “We aim to provide unbiased data on the diagnostic accuracy of OSNA in detecting CRC nodal metastases and feedback the practicalities of running such a service in a National Health Service (NHS) cellular pathology department”, we think the information given in their article is somehow incomplete. Their conclusions are based on the analysis of 99 lymph nodes (LNs) from a small cohort of 19 cases, with only 5.2 LNs examined per patient. Current guidelines, including the guidance of The Royal College of Pathologists, recommend that at least 12 LNs should be assessed to ensure an adequate specimen evaluation and a reliable pathologic staging.[1] In contrast, several studies using colon cancer OSNA lymph node analysis have assessed 12 or more LNs.[2–4]
    We agree with their statement that intraoperative OSNA detection of LN metastasis does not have a role in CRC surgery, mainly because regional lymphadenectomy is invariably included with the colectomy specimen. But this is not the target of molecular lymph node assessment in CRC. The most important clinical application of molecular LN analysis in CRC is that it enables a more precise staging in early CRC than the one obtained with conventional H&E analysis, especially useful for stage II pa...

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    Conflict of Interest:
    None declared.