her2 copy number cut-off point (by FISH) may be decreased (2.2to1.5)

[Lani]

This is the cut-off point they use to declare a tumor her2+/amplified and to date to propose that herceptin will be indicated. A large study or reevaluation of previous studies (cheaper) using this new proposed cut-off will be necessary to see if it better defines those in whom herceptin will decrease the rate of recurrence.


ABSTRACT: New cutpoints to identify increased HER2 copy number: analysis of a large, population-based cohort with long-term follow-up [Breast Cancer Research and Treatment]
Background: HER2 gene amplification and/or protein overexpression in breast cancer is associated with a poor prognosis and predicts response to anti-HER2 therapy. We examine the natural history of breast cancers in relationship to increased HER2 copy numbers in a large population-based study.
Patients and Methods: HER2 status was measured by fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC) in approximately 1,400 breast cancer cases with greater than 15 years of follow-up. Protein expression was evaluated with two different commercially-available antibodies.
Results: We looked for subgroups of breast cancer with different clinical outcomes, based on HER2 FISH amplification ratio. The current HER2 ratio cut point for classifying HER2 positive and negative cases is 2.2. However, we found an increased risk of disease-specific death associated with FISH ratios of >1.5. An 'intermediate' group of cases with HER2 ratios between 1.5 and 2.2 was found to have a significantly better outcome than the conventional 'amplified' group (HER2 ratio >2.2) but a significantly worse outcome than groups with FISH ratios less than 1.5.
Conclusion: Breast cancers with increased HER2 copy numbers (low level HER2 amplification), below the currently accepted positive threshold ratio of 2.2, showed a distinct, intermediate outcome when compared to HER2 unamplified tumors and tumors with HER2 ratios greater than 2.2. These findings suggest that a new cut point to determine HER2 positivity, at a ratio of 1.5 (well below the current recommended cut point of 2.2), should be evaluated.

[Rich66]

This dates back to '07. Anything further on this?

Can anyone explain where the Her-2 ratio scale begins and where it ends? From the post above, I assume it begins at 0, then at 2.1, it is currently considered "positive" however, how far does it go up?

[Lani]

Titre du document / Document title
New cutpoints to identify increased HER2 copy number : analysis of a large, population-based cohort with long-term follow-up
Auteur(s) / Author(s)
JENSEN K. C. (1) ; TURBIN D. A. (2) ; LEUNG S. (2) ; MILLER M. A. (2) ; JOHNSON K. (2) ; NORRIS B. (2) ; HASTIE T. (3) ; MCKINNEY S. (2) ; NIELSEN T. O. (2) ; HUNTSMAN D. G. (2) ; GILKS C. B. (2) ; WEST R. B. (3) ;
Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)
(1) Veterans Affairs Palo Alto Health Care System, Palo Alto, CA, ETATS-UNIS
(2) Genetic Pathology Evaluation Centre of the Vancouver Coastal Research Institute, British Columbia Cancer Agency and University of British Columbia, Vancouver, BC, CANADA
(3) Stanford University, Room L235, 300 Pasteur Drive, Stanford, CA 94305, ETATS-UNIS
Résumé / Abstract
Background HER2 gene amplification and/or protein overexpression in breast cancer is associated with a poor prognosis and predicts response to anti-HER2 therapy. We examine the natural history of breast cancers in relationship to increased HER2 copy numbers in a large population-based study. Patients and Methods HER2 status was measured by fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC) in approximately 1,400 breast cancer cases with greater than 15 years of follow-up. Protein expression was evaluated with two different commercially-available antibodies. Results We looked for subgroups of breast cancer with different clinical outcomes, based on HER2 FISH amplification ratio. The current HER2 ratio cut point for classifying HER2 positive and negative cases is 2.2. However, we found an increased risk of disease-specific death associated with FISH ratios of >1.5. An 'intermediate' group of cases with HER2 ratios between 1.5 and 2.2 was found to have a significantly better outcome than the conventional 'amplified' group (HER2 ratio >2.2) but a significantly worse outcome than groups with FISH ratios less than 1.5. Conclusion Breast cancers with increased HER2 copy numbers (low level HER2 amplification), below the currently accepted positive threshold ratio of 2.2, showed a distinct, intermediate outcome when compared to HER2 unamplified tumors and tumors with HER2 ratios greater than 2.2. These findings suggest that a new cut point to determine HER2 positivity, at a ratio of 1.5 (well below the current recommended cut point of 2.2), should be evaluated.
Revue / Journal Title
Breast cancer research and treatment ISSN 0167-6806 CODEN BCTRD6
Source / Source
2008, vol. 112, no3, pp. 453-459 [7 page(s) (article)] (33 ref.)
Langue / Language
Anglais
Editeur / Publisher
Springer, Dordrecht, PAYS-BAS (1981) (Revue)
Mots-clés anglais / English Keywords
Anatomic pathology ; Breast disease ; Mammary gland diseases ; Cancer ; Malignant tumor ; Human Epidermal growth factor Receptor 2 ; Survival ; Immunohistochemistry ; Gene overexpression ; Gene amplification ; Fluorescence in situ hybridization ; Breast cancer ; Follow up study ; Long term ; Cohort study ; Public health ; Analysis ; Copy number ; erbB2 Gene ; Protooncogene ; C-Onc gene ;
Mots-clés français / French Keywords
Anatomopathologie ; Pathologie du sein ; Pathologie de la glande mammaire ; Cancer ; Tumeur maligne ; Récepteur HER2 ; Survie ; Immunohistochimie ; Surexpression génique ; Amplification génique ; Hybridation in situ fluorescence ; Cancer du sein ; Etude longitudinale ; Long terme ; Etude cohorte ; Santé publique ; Analyse ; Nombre copie ; Gène erbB2 ; Protooncogène ; Gène onc cellulaire ;
Mots-clés espagnols / Spanish Keywords
AnatomÃ*a patológica ; Seno patologÃ*a ; Glándula mamaria patologÃ*a ; Cáncer ; Tumor maligno ; Sobrevivencia ; InmunohistoquÃ*mica ; Sobreexpresión genética ; Amplificación génica ; Hibridación in situ fluorescencia ; Cáncer del pecho ; Estudio longitudinal ; Largo plazo ; Estudio cohorte ; Salud pública ; Análisis ; Número copia ; Gen erbB2 ; Protooncogen ; Gen onc celular ;
Mots-clés d'auteur / Author Keywords
Breast cancer . Fluorescence in situ hybridization . HER2 amplification . Her2 overexpression ; Immunohistochemistry . Survival ;
Localisation / Location
INIST-CNRS, Cote INIST : 20699, 35400018402348.0070

Nº notice refdoc (ud4) : 20901940

[Laurel]

Lani,
Do you know the high end of Her2 amplification by FISH?

[Lani]

The directions on how to do the FISH testing includes the following:

Scoring/interpretation
In our laboratory, we use PathVysion, a FDA-approved kit for HER-2 testing by FISH and follow the scoring and interpretation recommended by the manufacturer. In this procedure, the chromosome 17 centromere is marked with a green florescent signal and HER-2 gene with an orange florescent signal. Briefly, we assess 60 non-overlapping tumor cell nuclei and count the number of green and orange signals in each cell. Then, the overall gene-to-chromosome (17) ratio is calculated. A tumor is designated as “positive� for gene amplification if gene-to-chromosome (17) ratio is >2.0



Detailed procedure
We use FDA approved PathVysion kit to assess HER-2 by FISH. As per manufacturers’ recommendation, 20 tumor non-overlapping cell nuclei are enumeratedto obtain the HER-2/chromosome 17 ratio.

So if they count twenty cells and all are her2+ with orange fluorescent signal and there is no polyploidy of chromosome 17 so the ratio is 1: 1 ie,
one her2+ orange fluorescence per chromosome 17 green fluorescence the ratio is 20:2 or a FISH of 10, but it may also be that they count 2 chromosomes I think the highest I have heard of was around 10, but my memory may be failing me..

[Lani]

ie why my answer in my above post was 20 and not 10:
There are two different commercial FISH tests currently in use

Two commonly used FISH assays are the Vysis PathVysion assay and the Ventana INFORM assay. The key difference is the inclusion of a probe for chromosome 17 in the Vysis assay but not in the Ventana assay. We analyzed our data using the interpretation guidelines of both assays. Only 3.9% of tumors (89/2,279) showed discrepant results between the 2 methods. The discrepancy apparently was due to polysomy 17 in tumors that were negative by D-FISH and positive by S-FISH and monosomy 17 with concurrent duplication of the HER-2 gene on the remaining chromosome 17 in tumors that were positive by D-FISH and negative by S-FISH, as suggested by other studies as well.[10,23,24] The present study does not permit a determination of which FISH assay is better for clinical testing.

Since the Ventana assay does not correct for the number of chromosome 17 and since it counts 20 cells, I guess FISH could theoretically be 20 if all 20 cells counted were + for her2.

SO 10-20 depending on which FISH test used.

Assuming that being Her-2 positive, a copying ratio above the current point of 2.2 per FISH and that being Her-2 positive correlates with a more "aggressive" tumor, would it be logical the higher the copying ratio, the more "aggressive" tumor? Also, if so, would it be logical, the higher the copying ratio, the more "receptors" Herceptin may have to connect with, thus rendering Herceptin even more effective? Any studies done on this?

[Debbie L.]

It has always interested me that at least in discussing Herceptin response and/or aggressiveness/prognostics, HER2 ratio by FISH doesn't offer quantitative prognostic nor predictive information. IOW, a high FISH ratio doesn't appear to mean that it's a worse prognosis nor a more-likely response to Herceptin. Yet on the lower end, we're not sure where the cut-off is, for Herceptin benefit.

That brings us to the question that I'm hearing more often lately - are we even looking at the right thing, when we look for a marker for those who can benefit from Herceptin, using HER2 by FISH or IHC? I don't know the answer of course - but neither, I suspect, does anyone else.

At present, we have only a somewhat-predictive thing - response for HER2+ to Herceptin is somewhere between 30 and 50% using current assays.

Debbie Laxague

[Rich66]

"are we even looking at the right thing"
Oh...always a big question, no?