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Table of Contents
Year : 2019  |  Volume : 2  |  Issue : 2  |  Page : 260-261

Author Reply to Chadha KG, et al.

Sapien Biosciences Private Limited, Hyderabad, Telangana, India

Date of Web Publication20-Dec-2019

Correspondence Address:
Jugnu Jain
Sapien Biosciences Private Limited, Apollo Health City, Jubilee Hills, Hyderabad - 500 096, Telangana
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/CRST.CRST_78_19

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How to cite this article:
Jain J. Author Reply to Chadha KG, et al. Cancer Res Stat Treat 2019;2:260-1

How to cite this URL:
Jain J. Author Reply to Chadha KG, et al. Cancer Res Stat Treat [serial online] 2019 [cited 2020 Apr 3];2:260-1. Available from: http://www.crstonline.com/text.asp?2019/2/2/260/273707

Regarding the letter to the editor, 'Reviewing ROS1 immunohistochemistry vis-à-vis fluorescence in situ hybridization (FISH) in non-small cell lung cancer' by Chadha et al.,[1] we are glad to note that the authors concur with our paper[2] and the editorial[3] that immunohistochemistry (IHC) presents a viable, more affordable alternative to FISH for ROS1 screening in non-small cell lung cancer (NSCLC). We are also glad to read that ROS1-positivity percentage in Chadha et al.'s experience was low, and similar to that of our study, both of which corroborate previous observations of <1% positivity of ROS1 by FISH in Indian patients. It would be useful to know how many of their 130 NSCLC cases tested for ROS1 were adenocarcinomas versus squamous cell carcinomas.

The authors suggest confirmation of ROS1 positivity by FISH. While this is ideal, in our experience, >90% of the patient samples are small biopsies which often do not have enough tissue left after testing for other markers such as EGFR and RAS to allow confirmation by FISH in practice. The cost of FISH assay is another factor for the patient to consider. Instead, a positive and negative control could be run simultaneously with the patient tissue as was done in our study in [Figure 1] to ensure both specificity and sensitivity of ROS1 antibody staining.[2] To explore implementation of this in routine IHC, we have contacted cell signaling technologies (CST) who provided the positive and negative control slides made from cell pellet blocks that were used in our study to optimize staining conditions [Figure 1]. The positive control was HCC78 cells overexpressing ROS1 mutation, and the negative control was HeLa cells that do not express Ros1 protein (references and data on CST website).[4] Being immortalized cell lines, these are unlimited resources that could be provided as cell blocks for pathology laboratories to section and place on the same slide as patient tissue for ROS1 staining.{Figure 1}

We await CST's response on the availability of these controls for routine ROS1 IHC to obviate the need to repeat testing of scarce tissue by FISH.

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Conflicts of interest

There are no conflicts of interest.

  References Top

Chadha KG, Barodawala SM, Patkar AJ. Reviewing ROS1 immunohistochemistry vis-à-vis fluorescence in situ hybridization in NSCLC. Cancer Res Stat Treat 2019;2:259-60.  Back to cited text no. 1
  [Full text]  
Jain J, Chinta D, Jayaraman UB, Pathak N, Kaur M, Chatterjee S, et al. Determination of ROS1 positivity by immunohistochemistry in a multicentric cohort of 426 nonsmallcell lung cancer cases in India. Cancer Res Stat Treat 2019;2:16-20.  Back to cited text no. 2
  [Full text]  
Choughule A, D'Souza H. ROS1 rearrangement testing: Is immunohistochemistry changing the horizon? Cancer Res Stat Treat 2019;2:66-8.  Back to cited text no. 3
  [Full text]  
Rimkunas VM, Crosby KE, Li D, Hu Y, Kelly ME, Gu TL, et al. Analysis of receptor tyrosine kinase ROS1-positive tumors in non-small cell lung cancer: Identification of a FIG-ROS1 fusion. Clin Cancer Res 2012;18:4449-57.  Back to cited text no. 4


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