SABC 2009
[6034] Heterogeneous Amplification of HER2 Is a Rare but Clinically Significant Event in Invasive Ductal Carcinoma.
Iurisci I, Cottu PH, Ngo C, Lae M, Pierga J-Y, Diéras V, Sigal-Zafrani B, Kirova Y, Mignot L, Vincent-Salomon A Institut Curie, Paris, France; Insitut Curie, Paris, France
Background
We have recently shown that pT1ab HER2 positive tumors carry a poor prognosis, which may be alleviated by trastuzumab (T) based therapy (Rodrigues et al, ASCO 2009). We had also reported that heterogeneous expression of HER2 (hetHER2) may be associated with a poor outcome depending on the HER2 overexpressing subclone (Cottu et al, Ann Oncol 2007). Meanwhile, ASCO/CAP guidelines have questioned the minimum valid score for HER2 expression (Moeder et al, J Clin Oncol 2007; Wolff et al, J Clin Oncol 2007). We describe here the characteristics and outcome of a series of patients with hetHER2 disease.
Patients and methods
HER2 status is routinely assessed in our institution in advanced breast cancer patients since 1999, and in early patients since 2002. Out of 1300 HER2 positive cases, we have been able to identify 12 pts with heterogeneous expression of HER2 in the primary tumor (<1%).
HetHER2 was defined as more than 5% and less than 59% of infiltrating cells overexpressing HER2 with an intense and complete membrane staining, and /or with a FISH ratio ≥ 2.2. Confirmation was obtained by FISH in 8 patients. Detailed pathological analysis, clinical characteristics and outcome were obtained.
Results
Median age at diagnosis was 45 years (31-64). All pts received adequate locoregional therapy according to institutional guidelines. Pathological characteristics of the primary tumors are depicted in the table.
Pathological Characteristics
| pT1 | pT2 | pT3 |
|---|
| Tumor Size (n) | 6 | 3 | 3 |
| n/ n evaluable | % |
|---|
| ER+ | 11/12 | 92 |
| PR+ | 5/12 | 42 |
| HER2 FISH+ | 8/10 | 80 |
| vascular emboli | 5/8 | 62.5 |
| pN0 | pNmi/i+ | pN+ |
|---|
| pN (n) | 6 | 2 | 4 |
| I / low | II / intermediate | III / high |
|---|
| Grade (Elston Ellis) | 2 | 5 | 5 |
| Mitotic Index | 3 | 2 | 7 |
|
All patients had infiltrating ductal carcinoma, two of them bearing also a ductal carcinoma in situ component. Most ER+ tumors had a faint staining, observed in less than 50% of tumor cells. In 1 pt with a node-positive tumor, the same pattern of heterogeneous overexpression of EHR2 was observed in the primary tumor and in the lymph nodes. Chemotherapy was given to 9 patients (75%), hormonal treatment to 6 pts (50%) and T was added to chemotherapy in 3 pts. With a median follow-up of 69 months (0-200), 6 pts have relapsed, none of them having received T based therapy. Median time to relapse was 46 mths (14-151). Initial sites of relapses were axillary lymph nodes (1), mediastinal lymph nodes (1), skin (1), liver (2) and ipsilateral relapse (1). No brain metastases were recorded. HER2 status was obtained in four relapses and was considered either negative (Skin), or highly overexpressed (liver) or heterogeneous (ipsilateral and axillary lymph node relapses). None of the 3 T treated pts has relapsed so far, but their follow up is still under 6 months.
Conclusions
More than half of the tumors exhibited at least 1 poor prognosis feature beyond HER2 overexpression.
In the line of the recent reanalysis of the NCCTG9831 adjuvant T trial which has suggested that T may be beneficial to hetHER2 patients (Sukov et al, ASCO 2009), our data support the evidence of a poor prognosis of hetHER2 disease, which may be similar to the prognosis of the “real” HER2 3+ and amplified disease. Prospective evaluation of anti HER2 based therapy in this subset of patients is clearly warranted.
Sunday, December 13, 2009 7:00 AM
Looking to Refine HER2-targeted Therapy
An illustration of HER proteins involved in an intracellular signaling pathway that controls cell growth HER proteins are part of an intracellular signaling pathway (depicted above) that is critical to many cellular functions. HER2 overexpression can lead to unchecked growth and, eventually, cancer. (Image courtesy of Genentech) Click to enlarge
When is a patient a candidate for a targeted therapy? That’s a question some breast cancer researchers are attempting to answer in the wake of results from several
studies presented in 2007 that suggested the definition of HER2-positive—that is, women whose breast tumors produce an excess of the HER2 protein—may be too strict. These
retrospective studies showed that even women who were HER2-negative benefited from the HER2-targeted agent trastuzumab (Herceptin). A monoclonal antibody, trastuzumab has been one of the most frequently cited success stories of the early era of molecularly targeted therapies. Its use improves progression-free and overall survival in women with HER2-positive metastatic breast cancer, and current data suggest it has a dramatic impact on the likelihood of cure for women with early stage HER2-positive disease.
Not all of the studies that continue trickling into the literature support the findings from those 2007 studies, but there is enough evidence, argued Dr. Peter Kaufman, professor of medicine at the Norris Cotton Cancer Center at the Dartmouth Hitchcock Medical Center, to suggest “that we may need to rethink conventional dogma.”
Hints of Something, but What?
Breast cancer experts agree that the recent studies are hypothesis-generating and should not dictate current clinical practice. After all, choosing breast cancer patients’ treatment based on HER2 status has been a successful paradigm, said Dr. Laura Esserman, who directs the breast cancer program at the Helen Diller Comprehensive Cancer Center at the University of California, San Francisco. “In general, targeting HER2 has proven to be the right thing to do,” she said. “I think it’s pretty clear that we’ve done a good job. It hasn’t been perfect, though. There’s room for improvement.”
The Measure of a Target IHC (immunohistochemistry) and FISH (fluorescence in situ hybridization) are the two testing methods recommended in the ASCO/CAP HER2-testing guidelines, which detail how the tests should be performed and what constitutes HER2-positive, -negative, and equivocal or borderline results.
The IHC assay measures the amount of HER2 protein expressed in cancer cells, while the FISH assay measures either the total number of copies of the HER2 gene in a tumor cell or the ratio of HER2 genes to chromosome 17 copies. Result IHC FISH (two approaches) Positive 3+ <6 HER2 copies per cell or HER2:ch 17 ratio of 2.2 to 1 Negative 0+, 1+ <4 HER2 copies per cell or HER2:ch 17 ratio <1.8 to 1 Equivocal 2+ 4 – 5 HER2 copies or 1.8 – 2.2 HER2:ch 17 ratio
For example, researchers would like to find ways to improve the response rate to trastuzumab, which hovers between 25 and 30 percent. There are also misgivings about the accuracy of HER2 testing, concerns that were significant enough to prompt the American Society of Clinical Oncology (ASCO) and College of American Pathologists (CAP) to develop clinical guidelines for HER2 testing. “This is a tumor marker that’s being used as the sole determinant of therapy selection,” explained the guidelines panel co-chair, Dr. Antonio C. Wolff of the Johns Hopkins Sidney Kimmel Comprehensive Cancer Center. “That’s why it’s important that pathologists do their best to adhere to the guidelines and clinicians ask questions about the quality of testing.” It’s also critical to continue clinical research on the use of HER2-targeted therapies like trastuzumab and lapatinib (Tykerb), Dr. Wolff added. “You need to be confident that you’re talking about true HER2-positive or -negative tumors. Then you can start looking at clinical outcomes,” he said. The response rate and accuracy issues overlap with the questions about the definition of HER2-positive, which is most commonly determined with two tests, IHC and FISH. (See sidebar.) The IHC and FISH cutoffs that correspond with response to trastuzumab were established based on clinical trials involving women with metastatic breast cancer, explained Dr. Tracy Lively, associate chief of the Diagnostics Evaluation Branch in NCI’s Division of Cancer Treatment and Diagnosis. The recent data, she added, suggest that
perhaps those cutoffs may need to be modified for women being treated for early stage disease. At the 2007 ASCO annual meeting, Dr. Soonmyung Paik, director of the Division of Pathology for the National Surgical Adjuvant Breast and Bowel Project (NSABP) in Pittsburgh, first suggested the same thing.
Dr. Paik and his colleagues had conducted an unplanned, retrospective analysis of available tumor samples from the
B-31 trial, which compared adjuvant chemotherapy and trastuzumab to chemotherapy alone in women with HER2-positive, early stage breast cancer. After retesting the tumor blocks, they found that 10 percent were truly HER2-negative (meaning the women shouldn’t have been enrolled in the trial). Nevertheless,
there was a statistically significant trend toward improved outcomes in HER2-negative patients treated with trastuzumab. In fact, every HER2-negative patient subset saw some benefit, although not all reached statistical significance. The findings were consistent with data from two other studies presented at the meeting, including another unplanned, retrospective analysis led by Dr. Kaufman of tumor samples from women with metastatic breast cancer in the CALGB 9840 trial. Some women in the trial whose tumors were HER2-negative according to FISH but who also had polysomy of chromosome 17—extra copies of chromosome 17, where the HER2 gene resides—had improved response rates to treatment with trastuzumab and chemotherapy compared to chemotherapy alone. “That raised a fair number of eyebrows,” Dr. Kaufman said. “But, again, these findings are preliminary. It could just be a fluke due to the small sample size and retrospective analysis.”
Data on this topic continue to emerge, including a recent study led by Dr. Michael Press from the Norris Comprehensive Cancer Center at the University of Southern California, which found no benefit from lapatinib in HER2-negative women. Where to Go from Here A large clinical trial is needed to determine whether some women, whose tumors reside somewhere in the molecular middle between HER2-negative and -positive, could benefit from HER2-targeted therapy, said Dr. Lively. Such a study could be on the horizon. A validation study to confirm the results from Dr. Paik’s earlier study “is moving forward quickly,” explained NSABP Director of Medical Affairs Dr. Charles Geyer. If the results are positive, he continued, NSABP plans to conduct a clinical trial that would look at whether women with breast tumors that fall into a “HER2-low” category may benefit clinically from HER2-targeted therapy. In the meantime, Dr. Esserman said, although the available data have raised some tough questions, she sees a positive side. “It’s not necessarily that these assays are wrong,” she said. “Maybe there’s just a better way to measure.” Dr. Esserman, for instance, is a co-principal investigator of a clinical trial of neoadjuvant chemotherapy for women with early stage breast cancer called I-SPY. The trial is using molecular analyses of serial biopsies and serial MRI scans to identify markers of response to treatment.
One area showing promise, she noted, is the correlation of the levels of phosphorylated HER2 protein (the addition of phosphate groups to the protein, which regulates its activity) with other measures of HER2 expression and response to trastuzumab. Much further along the clinical spectrum is an assay developed by San Francisco-based Monogram Biosciences called HERmark. According to the company, the assay provides a more exact measurement of HER2 levels, as well as the extent of the complexes formed by HER2 proteins on the surface of cancer cells (called dimers). Smaller studies presented at national meetings have suggested the assay can more accurately predict which women, including those who are HER2-positive, will respond to trastuzumab. “Without the controversy,” Dr. Esserman said, “I don’t think there would be as much motivation to develop new and better assays.” —Carmen Phillips
Ann Surg Oncol. 2009 Oct 17. [Epub ahead of print]
Characterizing the HER2/neu Status and Metastatic Potential of Breast Cancer Stem/Progenitor Cells.
Pommier SJ,
Quan GG,
Christante D,
Muller P,
Newell AE,
Olson SB,
Diggs B,
Muldoon L,
Neuwelt E,
Pommier RF.
Division of Surgical Oncology, Department of General Surgery, Oregon Health & Science University, Portland, OR, USA,
pommiers@ohsu.edu.
INTRODUCTION: Treatment resistance, long latency, and high recurrence rates suggest that breast cancers arise from defective breast stem cells. HYPOTHESIS: Within cancers, subpopulations of cells will demonstrate differences in stem/progenitor potential, HER2/neu amplification, and gene expression. Related cells will be found in normal breast tissue. METHODS: ER-/PR-/HER2/neu + breast cancer cells were flow-sorted into subpopulations: (A) CD49f(+) CD24(-), (B) CD49f(+)CD24(+), (C) CD49f CD24(-), and (D) CD49f(-)CD24(+). Gel matrix cell invasion, fluorescence in situ hybridization (FISH) HER2/neu amplification, and qRT-PCR gene expression were measured in all groups. Cells from sorted groups were implanted into rat brains. Resultant tumors were analyzed by immunohistochemistry (IHC) and FISH. Normal breast tissue was examined by IHC. RESULTS: Tumor development varied among sorted groups (25-75%), but was highest in group A. Tumor cells were mostly CD49f(-)CD24(-), with variable fractions of other stem/progenitor cells. Tumors showed HER2/neu amplification, but fewer chromosome 17 per cell than inoculates. Group A tumors exhibited cells with normal chromosome 17 copy number and near normal HER2/neu amplification. Cell invasion was 61% higher in unsorted cells and 34-42% in sorted groups compared with controls. Sorted groups showed significantly different expression of development, proliferation, and invasion associated genes. In normal breast tissue, CD49f(+) cells were identified in CD14(+) CK19(-) basal epithelial layers of mammary glands; these were 95% CD24(+) and 60% CD44(+). CONCLUSIONS:
Breast cancer stem/progenitor cell populations differ in tumor-initiating potential but are not solely responsible for metastasis. Cancer stem/progenitor cells are less polyploid than cancer cells in general and may not be HER2/neu amplified. In normal breast tissue, breast stem/progenitor cell-like populations are present.
PMID: 19838757 [PubMed - as supplied by publisher]
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