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Testing for her2/neu in breast cancer at the time of primary diagnosis is now the standard of care. Accurate and standardized testing methods are of prime importance to ensure the proper classification of the patient’s her2/neu status. A meeting of pathologists from across Canada was convened to update the Canadian her2/neu testing guidelines. This National her2/neu Testing Committee reviewed the recently published American Society of Clinical Oncology/ College of American Pathologists (asco/cap) guidelines for her2/neu testing in breast cancer. The updated Canadian her2/neu testing guidelines are based primarily on the asco/cap guidelines, with some modifications. It is anticipated that widespread adoption of these guidelines will further improve the accuracy of her2/neu testing in Canada.
The human epidermal growth factor 2 (her2/neu) gene is amplified in approximately 18%–20% of breast cancers 1–4, and it is the primary mechanism for her2 protein overexpression 5. Overexpression of her2 is predictive of response to particular therapies, including trastuzumab (Herceptin: Genentech, San Francisco, California, U.S.A.) treatment in the meta-static and adjuvant settings 1,6–10.
Recognizing the importance of accurate her2/neu status assessment, pathologists from across Canada gathered to share local testing experiences and insights. The meeting was chaired by Dr. Wedad Hanna and Dr. Frances P. O’Malley, who facilitated the collaboration to create a Canadian consensus statement for her2 testing procedures.
The American Society of Clinical Oncology (asco) and the College of American Pathologists (cap) convened an expert panel to develop a U.S. guideline to improve the accuracy of her2 testing in invasive breast cancer. This asco/cap guideline was reviewed by the panel of Canadian pathologists. The data from that review and the experience of the panel members were used to create the current update of the Canadian her2 testing guidelines and algorithm (Figure 1). The updated information is presented here.
Wedad Hanna md (Toronto, Ontario) and Frances P. O’Malley md (Toronto, Ontario)
Penelope Barnes md (Halifax, Nova Scotia), Richard Berendt md (Edmonton, Alberta), Louis Gaboury md (Montreal, Quebec), Anthony Magliocco md (Calgary, Alberta), Norman Pettigrew md (Winnipeg, Manitoba), Susan Robertson md (Ottawa, Ontario), Sandip Sengupta md (Kingston, On-tario), Bernard Têtu md (Québec City, Quebec), and Thomas Thomson md (Vancouver, British Columbia)
The information that follows is based both on the experience of the consensus participants and on the recently published asco/cap Guideline Recommendations for her2/neu Testing in Breast Cancer.
The her2/neu gene has proved to be a significant prognostic and predictive biologic marker in breast cancer 1. Thus, the current standard of care is to test all patients with invasive breast cancer for her2/neu at the time of diagnosis 1.
The panel agreed that standardized and validated tests should be performed. Available data do not show superiority for either immunohistochemistry (ihc) or in situ hybridization (ish) as a predictor of benefit from Herceptin therapy. The testing algorithm proposed for all invasive breast cancers is based on the very high concordance between her2/neu gene amplification and protein expression as determined using accurate and reproducible assay methods. Thus, the Canadian consensus agrees with the asco/cap guidelines and is based on testing first with ihc and then retesting equivocal cases using ish [either fluorescent (fish) or another validated brightfield ish method such (as chromogenic cish) or silver-enhanced (sish)] 1. Throughout the current document, the use of fish methodology is not exclusive; labs can use other validated ish methods to assess equivocal cases both for clinical case and quality assurance (qa) activities.
The guidelines and variables related to accurate testing are discussed under the headings pre-analytic, analytic, and post-analytic.
Time from specimen excision to placement in fixative should be minimized. Samples should be sliced immediately at 5–10 mm intervals after appropriate gross inspection and designation of margins and then placed in a sufficient volume of 10% neutral buffered formalin 1. Optimal time of fixation is 24–48 hours in 10% neutral buffered formalin, but a period of at least 6 hours 11 is sufficient for core biopsy specimens. A fixation time longer than 48 hours for lumpectomy/ mastectomy specimens is not an exclusion criterion for her2 testing (Table I) provided that the specimen has been appropriately sectioned to allow adequate fixation as described above. Under-fixation is more critical than over-fixation; less than 6 hours’ fixation time precludes the specimen from being used for her2 testing. The fixation requirements described above pertain to testing both with ihc and with fish.
When validating a new antibody, 25–100 samples should be tested 1. However, if the lab has little experience with performing her2 testing, a minimum of 100 sample tests is advisable. An assay accuracy of 95% concordance rate should be achieved for both the positive and negative categories. Adequate validation should be ensured, preferably by using 50% cases that are unequivocally positive and 50% cases that are unequivocally negative. Validation documentation must be kept. Any modification to the procedure requires additional validation to ensure accurate performance.
Stringent compliance to validated standard operating procedures developed in assay validation must be adhered to and quality control (qc) documentation must be in place.
The controls should include positive (overexpressed/ amplified) and negative (not overexpressed/not amplified) cases, plus a low amplified/low protein over-expression case if possible. The control tissue should be fixed and processed in the same manner as the patient samples.
The use of correctly operated automated staining protocols and equipment are acceptable, but validated methods must be used. Maintenance and service records should be regularly updated and filed in the laboratory.
Use of image analysis systems can be useful to enhance reproducibility of scoring; pathologists must supervise all image analyses.
The panel agreed that mandatory reporting elements testing include these items for ihc 1:
The panel agreed that mandatory reporting elements for fish testing include these items1:
Per the United Kingdom guidelines, each lab should tests perform at least 250 ihc 12. If the lab also performs fish, then at least 100 fish tests should be performed annually. However, given the complexity of the procedure and the experience needed, it is advisable and preferable to perform at least 200 fish tests annually.
Appropriate training for pathologists should take place, and the number of tests performed by each pathologist should be considered to ensure competency. Test volume should be assessed in conjunction with the lab’s adherence to strict qc and qa practices. Technologists should undergo appropriate training, including ongoing education in fish technology and interpretation.
The panel recommends that initial test validation should take place together with ongoing qc and equipment maintenance. Initial and ongoing education of laboratory personnel, training, and competency assessment should also be implemented. The use of standardized operating procedures, including routine use of control materials, should be enforced, and modified procedures should be revalidated. Finally, ongoing competency assessment and education of pathologists should take place.
The panel agreed that participation in an external proficiency testing program with at least two testing events (mailings) annually is mandatory. Also, satisfactory performance requires at least 90% correct responses in graded challenges for either test. Unsatisfactory performance will require a laboratory to respond according to accreditation agency program requirements.
Onsite inspection should take place every other year with an annual requirement for self-inspection. Review of laboratory validation, procedures, qa results and processes, results, and reports should be put into place. Unsatisfactory performance results in suspension of laboratory testing for her2 for that method.
“Sensitivity” is defined as the percentage of positive test results obtained when evaluating only specimens that are truly positive. “Specificity” is defined as the percentage of negative test results reported when only truly negative specimens are evaluated. “Overall accuracy” (concordance) combines sensitivity and specificity into a single measure of the percentage of cases (positive and negative) for which the assay result agrees with the true status. Note that overall accuracy (concordance rate) can be strongly influenced by the positive–negative mix of the test case set if the sensitivity and specificity rates are not similar.
Examples of external qa programs include these:
The panel agreed that pathologists should test at diagnosis, starting with ihc and then, in equivocal cases, moving to fish or to another validated brightfield in situ hybridization method such as cish or sish. In cases in which the available sample is small or the sample is a core biopsy in the neoadjuvant setting, it is preferable to perform ish as the initial test (Figure 1).
Considering the prognostic and predictive significance of determining her2/neu status in invasive breast cancer, her2/neu testing performed at the time of initial diagnosis is now the standard of care. In line with the updated asco/cap guidelines, the Canadian consensus guidelines provide recommendations on how to evaluate and report her2/neu over-expression and gene amplification. In summary, the guidelines outline specific criteria that laboratories must meet before engaging in her2/neu testing.
The 2007 her2/neu testing algorithm integrates both the ihc and the fish algorithms as published in the asco/cap guidelines. It is important to note that the cut-offs for positivity for both ihc and fish have been updated; a positive ihc result is now defined as >30% strong complete membrane staining; a positive fish result is defined as a ratio > 2.2 or a her2 gene copy > 6.0.
With continual efforts being made to optimize her2/neu testing accuracy, the testing guidelines and algorithm will be regularly updated to convey current practices.
We thank Hoffmann–La Roche Canada for providing funding for the National Consensus Meeting and development of this consensus document.
a“Tile” is the unit used for image-system counting.