- Email: [email protected]
P053 Serum HER2 extracellular domain before surgery compared with HER2 in breast cancer
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Poster Abstracts I / The Breast 24S1 (2015) S26–S86
Furthermore, LR cell lines proliferated by E1S in dose-dependent manner more than their parental cells, but there was no difference of proliferation when estrone and estradiol treated. STS inhibitor administered with letrozole was inhibitory to proliferation of LR cells. LR cells were also inhibited by SERM and SERD. In mRNA analysis of clinical primary tissues of postmenopausal patients, expression of STS mRNA significantly correlated with those of three OATPs which were induced in LR cell lines. Conclusion: In this study, we first demonstrated that the contribution of E1S to ER-positive breast cancer in the context of AI resistance. Targeting therapy to E1S–STS pathway could present a new choice of treatments to AI-resistant breast cancer patients, especially by combination with AI. Disclosure of Interest: No significant relationships. P051 Photoacoustic imaging of breast cancer and histological markers of angiogenesis E. Fakhrejahani1 *, M. Torii1 , I. Yamaga1 , Y. Asao1 , T. Kitai2 , M. Kataoka3 , S. Kanao3 , M. Takada1 , T. Shiina4 , M. Toi1 . 1 Department of Breast Surgery, Kyoto University, Kyoto, Japan, 2 Department of Surgery, Kishiwada City Hospital, Osaka, Japan, 3 Department of Diagnostic Radiology, Kyoto University, Kyoto, Japan, 4 Department of Human Heath Scinece, Kyoto University, Kyoto, Japan Goals: Photoacoustic mammography (PAM) non-invasively can visualize breast cancer vasculature and provide information about the hemoglobin oxygenation level (SO2 ) in breast lesions. We presented clinical study of the first prototype PAM-01 (CK project) during San Antonio Breast Cancer Symposium 2014 and reported that in almost 3 out of four cases, lesion associated signals were detectable. The correlation between microvessel perimeter as well as carbonic anhydrase IX (CAIX) expression with SO2 was also reported. In order to better understand the tumor microvessel characteristics which might have an impact on PAM signals, we analyzed microvessel maturity of central area of all lesions. Methods: Histological sections from the widest area of the lesions were evaluated post-excisional by immunohistochemistry using anti-smooth muscle actin (SMA) as pericyte marker. Histological slides were scanned (Hamamatsu Inc. Japan). A 3.36×3.36 mm area from the central part of each tumor (excluding possible necrosis) was extracted and divided into 100 smaller squares using a 10×10 grid. Squares with minimum one vessel positive for SMA were counted and the total count/100 squares was considered as central tumor vessel maturity index (TVMI). Results: The median of TVMI in total cases was 61.5% (15–91%). There was no difference between TVMI of visible and non-visible cases (63% vs. 60%). TVMI showed no correlation to size, grade and Ki67 index of the tumors. Invasive cancer positive for CAIX showed higher total vascular perimeter in comparison with CAIX negative cancers (8.51 vs. 4.44, p-value 0.027, Mann–Whitney U test) while TVMI was the same (62.5% vs. 61.5%). History of neoadjuvant treatment did not show any effect on TVMI (60% for cases without vs. 61% for cases with treatment). SO2 did not show difference between cases with low vs. high TVMI (72.7% vs. 68.3%, p = 0.8, Mann–Whitney U test). Conclusion: Although vessel maturity did not show any correlation to visibility or measured SO2 , the second generation PAM (PAM-02) which is now under a clinical evaluation study and has higher resolution and a built-in ultrasound will be able to provide more accurate information on breast cancer functional imaging. At the same time, further study on tumor vasculature shape is necessary to better understand the correlation between histology and oxygenation data of breast cancers. Disclosure of Interest: Yasufumi Asao is an employee of Canon Inc.
P052 Identification and targeting of Wnt-driven breast cancers V. Arndt *, E. Meuser, J. Waak, K. Ross, F. Agerer, A. Friebe, J. Vollmer. Late Discovery, Nexigen GmbH, Cologne, Germany Goals: Targeted inhibition of oncogenic Wnt signaling holds great promise for the treatment of various cancers. For instance, dysregulation of the Wnt pathway has been associated with several aggressive breast cancer subtypes. In breast cancer, pathway activation has been shown to play a critical role in tumor growth, metastasis and chemoresistance, indicating that Wnt inhibitors could have therapeutic benefit for breast cancer patients. Targeting of the Wnt pathway, however, has been difficult in practice due to the lack of druggable targets and a defined susceptible patient population. Using our proprietary next generation peptide screening platform, we have previously identified a cell-permeable Wnt peptide inhibitor that effectively inhibits tumor growth and metastasis in different in vitro and in vivo models of triple-negative breast cancer. In the present study, we aimed to better define breast cancer tumors that can be targeted by our peptide inhibitor. Methods: For this purpose, we analyzed the expression of Wnt pathway components by Western Blot in a representative panel of breast cancer cell lines. Autocrine and paracrine Wnt pathway activation was assessed through b-catenin stabilization and target gene expression. Different Wnt inhibitors were used to study the effect of Wnt pathway blockage on tumor growth and metastasis in several cell-based assays. Results: In contrast to colorectal cancer, oncogenic activation of the Wnt pathway in breast cancer is rather based on alterations in expression level and/or autocrine/paracrine stimulation of the pathway than genetic mutations. Analysis of the expression levels indeed showed significant differences in the expression of Wnt pathway components between the different breast cancer cell lines. In accordance with this finding, assessment of autocrine and paracrine pathway activation revealed a set of Wnt-responsive cell lines. Treatment with different Wnt pathway inhibitors or knockdown of b-catenin in these cell lines resulted in decreased cell proliferation, migration and tumorsphere formation, indicating that some breast cancers could benefit from therapeutic inhibition of Wnt signaling. Conclusion: In summary, our Wnt pathway peptide inhibitor could be a promising new drug candidate to be interrogated for the treatment of breast cancer stem cells and a defined subset of breast cancer tumors. Disclosure of Interest: All contributors are employees of Nexigen GmbH. A. Friebe and J. Vollmer additionally are shareholders of Nexigen GmbH. P053 Serum HER2 extracellular domain before surgery compared with HER2 in breast cancer J. Zidan1 *, R. Mzalbat2 , A. Sharabi2 . 1 Oncology, Oncology Institute. Ziv Medical Center, Safed, Israel, 2 Ziv Medical Center, Safed, Israel Goals: Human epidermal growth factor receptor 2 (HER2) is an important prognostic and predictive factor in breast cancer (BC). The importance HER2 extracellular domain (ECD) in serum is not yet determined. The aim of this study was to explore the correlation between serum ECD and tissue HER2 expression, clinical and pathological features in primary BC. Methods: In this prospective study only patients with stage I–III BC were included. Serum ECD levels were measured by ADVIA Centaur automated assays before surgical resection of the tumor. Serum ECD >15 ng/ml was considered to be positive. Results: Eighty patients with breast tumors were included. Stage I–III BC was diagnosed in 64 patients, Ductal carcinoma in situ in 9 and
14th St.Gallen International Breast Cancer Conference / The Breast 24S1 (2015) S26–S86
benign tumors in 7 patients. HER2 overexpression was observed in 8 of 64 patients (16.4%). Mean value of serum ECD was 10.9 ng/ml (range: 6.7 to 21.5). Four (6.2%) of the 64 patients had high ECD levels and in 60 (93.8%) patients lower levels of ECD were found. No significant relationship was found between ECD levels and tissue HER2 overexpression. ECD was higher in women aged >40 than in women <40. ECD was higher in Arab than in Jewish patients. No significant relation was found between ECD and all clinical and pathological features. Conclusion: The sensitivity of HER2 ECD for the diagnosis of HER2 overexpression in primary breast cancer is poor. No significant correlation was found between ECD levels and tissue HER2 expression, clinical and pathological characteristics of primary BC. Disclosure of Interest: No significant relationships. P054 Embryonic stem cells and BR CA risk & prognosis in a North Indian cohort: multi-analytical study G. Agarwal1 *, S. Tulsiyan2 , P. Lal3 , B. Mittal2 . 1 Endocrine & Breast Surgery, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India, 2 Genetics, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India, 3 Radiation Oncology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India Goals: Variations in surface biomarkers (CD44) and regulatory genes (OCT4, SOX2, NANOG, LIN28) of Embryonic Stem Cells (ESCs) may lead to breast cancer cell growth, differentiation and metastasis. We studied the role of ESCs gene polymorphisms in breast cancer risk and prognosis using multi-analytical strategies in a North Indian breast cancer patient cohort and healthy controls. Methods: Polymorphisms in CD44 (rs353639, rs13347), OCT4 (rs3130932), NANOG (rs11055786), LIN28 (rs4274112) and SOX2 (rs11915160) genes were evaluated in 258 females North Indian breast cancer patients and 205 healthy controls. Response to neoadjuvant chemotherapy (NACT) was evaluated per RECIST criteria in 114 patients. Taqman allelic discrimination assays were used for genotyping. Statistical analysis was performed using SPSS and GMDR. Online browser F-SNP was used for in-silico analysis for prediction of functional effects. Results: Comparing the OCT4 gene polymorphism in breast cancer patients and healthy controls, a protective effect of genotypes AC [P = 0.016, OR = 0.64 (0.44–0.92)] and AC+CC [P = 0.019, OR = 0.62 (0.42–0.92)] was apparent. In SOX2 rs11915160, AC [P = 0.017, OR = 2.93 (1.21–7.09)] and AC+CC [P = 0.011, OR = 3.09 (1.28–7.43)] genotypes were found associated with breast cancer risk. No association of CD44, NANOG, and LIN28 gene polymorphisms were found with breast cancer risk. For CD44 rs353639 polymorphism, AC+CC genotype [P = 0.017, OR = 4.29 (1.30–14.11)] and C allele [P = 0.025, OR = 3.34 (1.16–9.59)] were significantly correlated with tumour size. However, no association was seen with CD44 rs13347. Significant association of AG+GG genotype [P = 0.021, OR = 6.08 (1.83–20.15)] and G allele [P = 0.021, OR = 3.07 (1.21–7.77)] of LIN28 rs4274112 polymorphism were seen with lymph node metastases. For OCT4 rs3130932, significant association of allele C was seen with hormone receptor negative status [Sr = 0.021, OR = 0.51 (0.29– 0.90)]. None of the studied polymorphisms individually were found correlated with response to NACT. On GMDR analysis, we found combination of SNPs OCT4 rs3130932, NANOG rs11055786 to be the best interaction model for predicting breast cancer risk [CVC = 8/10] and OCT4 rs3130932, LIN28 rs4274112 for response to NACT [CVC = 9/10]. In-silico analysis using F-SNP, showed altered transcriptional regulation for rs353639, rs13347, rs11915160 and rs4274112 polymorphism. However, rs3130932 showed change in protein coding mechanism and rs11055786 in splicing regulation.
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Conclusion: Combination of genetic variants in ESC genes may have influence in both breast cancer susceptibility and poor response to NACT in north Indian breast cancer patients. Disclosure of Interest: No significant relationships. P055 Clinical dilemma of contradictory HER2 results in breast cancer resolved by microarrays M.J. Kotze1 *, E. Murray2 , H.K. Lukhoff1 , K. Grant1 . 1 Pathology, Stellenbosch University, Cape Town, South Africa, 2 Private Oncology Practice, Cape Town, South Africa Goals: The study was performed at the interface between the laboratory and oncology practice in an attempt to address the clinical dilemma presented by equivocal and contradictory results for human epidermal growth factor receptor-2 (HER2) status frequently obtained in patients with early-stage breast cancer. The aim was to evaluate whether microarray gene profiling might provide additional benefit under these circumstances. The high false-negative rate of HER2 status reported with use of Oncotype DX cautions against the use of reverse transcriptase polymerase chain reaction (RT-PCR) technology for selection of breast cancer patients for HER2 targeted treatment. Methods: Microarray analysis was performed using RNA extracted from 41 fresh tumour biopsies and 119 formalin-fixed paraffin embedded (FFPE) tissue specimens. Three lines of genomic information based on MammaPrint, TargetPrint and BluePrint were obtained over and above standard immunohistochemistry/ fluorescence in situ hybridisation (IHC/FISH) to help guide treatment decisions. Results: We demonstrated 100% agreement of HER2 status following IHC/FISH reflex testing in all five discordant cases identified (Grant et al. in press). In a further patient suffering from idiopathic thrombocytopenic purpura and who presented with contradictory IHC/FISH findings, the following results were obtained that support a low risk for distant recurrence: 1) MammaPrint (70 genes): Low-risk profile, despite HER2 copy number of 6.5 compatible with HER2positive status according to the ASCO/CAP guidelines. 2) TargetPrint (3 genes): HER2-negative, in accordance with the HER2/CEP17 ratio of 1.5 considered compatible with HER2-negative status according to local guidelines for HER2 assessment (modified in November 2014 partly as a result of this comparative study) 3) BluePrint (80genes): Luminal A subtype, which is associated with HER2-negative status (excluded the HER2-enriched and Luminal B subtypes mostly associated with HER2-positive status). Conclusion: Determination of HER2 status across three assay platforms facilitated improved quality assurance and led to a higher level of confidence on which treatment decisions were based. Equivocal and contradictory IHC/FISH results and borderline HER2 cases have become important considerations when either Oncotype DX or the MammaPrint microarray is requested in South African patients. Breast cancer patients with rare categories of HER2 status not adequately covered by existing guidelines may also benefit from objective microarray gene profiling. Disclosure of Interest: Prof MJ Kotze is a shareholder and director of Gknowmix (Pty) Ltd.
Poster Abstracts I / The Breast 24S1 (2015) S26–S86
Furthermore, LR cell lines proliferated by E1S in dose-dependent manner more than their parental cells, but there was no difference of proliferation when estrone and estradiol treated. STS inhibitor administered with letrozole was inhibitory to proliferation of LR cells. LR cells were also inhibited by SERM and SERD. In mRNA analysis of clinical primary tissues of postmenopausal patients, expression of STS mRNA significantly correlated with those of three OATPs which were induced in LR cell lines. Conclusion: In this study, we first demonstrated that the contribution of E1S to ER-positive breast cancer in the context of AI resistance. Targeting therapy to E1S–STS pathway could present a new choice of treatments to AI-resistant breast cancer patients, especially by combination with AI. Disclosure of Interest: No significant relationships. P051 Photoacoustic imaging of breast cancer and histological markers of angiogenesis E. Fakhrejahani1 *, M. Torii1 , I. Yamaga1 , Y. Asao1 , T. Kitai2 , M. Kataoka3 , S. Kanao3 , M. Takada1 , T. Shiina4 , M. Toi1 . 1 Department of Breast Surgery, Kyoto University, Kyoto, Japan, 2 Department of Surgery, Kishiwada City Hospital, Osaka, Japan, 3 Department of Diagnostic Radiology, Kyoto University, Kyoto, Japan, 4 Department of Human Heath Scinece, Kyoto University, Kyoto, Japan Goals: Photoacoustic mammography (PAM) non-invasively can visualize breast cancer vasculature and provide information about the hemoglobin oxygenation level (SO2 ) in breast lesions. We presented clinical study of the first prototype PAM-01 (CK project) during San Antonio Breast Cancer Symposium 2014 and reported that in almost 3 out of four cases, lesion associated signals were detectable. The correlation between microvessel perimeter as well as carbonic anhydrase IX (CAIX) expression with SO2 was also reported. In order to better understand the tumor microvessel characteristics which might have an impact on PAM signals, we analyzed microvessel maturity of central area of all lesions. Methods: Histological sections from the widest area of the lesions were evaluated post-excisional by immunohistochemistry using anti-smooth muscle actin (SMA) as pericyte marker. Histological slides were scanned (Hamamatsu Inc. Japan). A 3.36×3.36 mm area from the central part of each tumor (excluding possible necrosis) was extracted and divided into 100 smaller squares using a 10×10 grid. Squares with minimum one vessel positive for SMA were counted and the total count/100 squares was considered as central tumor vessel maturity index (TVMI). Results: The median of TVMI in total cases was 61.5% (15–91%). There was no difference between TVMI of visible and non-visible cases (63% vs. 60%). TVMI showed no correlation to size, grade and Ki67 index of the tumors. Invasive cancer positive for CAIX showed higher total vascular perimeter in comparison with CAIX negative cancers (8.51 vs. 4.44, p-value 0.027, Mann–Whitney U test) while TVMI was the same (62.5% vs. 61.5%). History of neoadjuvant treatment did not show any effect on TVMI (60% for cases without vs. 61% for cases with treatment). SO2 did not show difference between cases with low vs. high TVMI (72.7% vs. 68.3%, p = 0.8, Mann–Whitney U test). Conclusion: Although vessel maturity did not show any correlation to visibility or measured SO2 , the second generation PAM (PAM-02) which is now under a clinical evaluation study and has higher resolution and a built-in ultrasound will be able to provide more accurate information on breast cancer functional imaging. At the same time, further study on tumor vasculature shape is necessary to better understand the correlation between histology and oxygenation data of breast cancers. Disclosure of Interest: Yasufumi Asao is an employee of Canon Inc.
P052 Identification and targeting of Wnt-driven breast cancers V. Arndt *, E. Meuser, J. Waak, K. Ross, F. Agerer, A. Friebe, J. Vollmer. Late Discovery, Nexigen GmbH, Cologne, Germany Goals: Targeted inhibition of oncogenic Wnt signaling holds great promise for the treatment of various cancers. For instance, dysregulation of the Wnt pathway has been associated with several aggressive breast cancer subtypes. In breast cancer, pathway activation has been shown to play a critical role in tumor growth, metastasis and chemoresistance, indicating that Wnt inhibitors could have therapeutic benefit for breast cancer patients. Targeting of the Wnt pathway, however, has been difficult in practice due to the lack of druggable targets and a defined susceptible patient population. Using our proprietary next generation peptide screening platform, we have previously identified a cell-permeable Wnt peptide inhibitor that effectively inhibits tumor growth and metastasis in different in vitro and in vivo models of triple-negative breast cancer. In the present study, we aimed to better define breast cancer tumors that can be targeted by our peptide inhibitor. Methods: For this purpose, we analyzed the expression of Wnt pathway components by Western Blot in a representative panel of breast cancer cell lines. Autocrine and paracrine Wnt pathway activation was assessed through b-catenin stabilization and target gene expression. Different Wnt inhibitors were used to study the effect of Wnt pathway blockage on tumor growth and metastasis in several cell-based assays. Results: In contrast to colorectal cancer, oncogenic activation of the Wnt pathway in breast cancer is rather based on alterations in expression level and/or autocrine/paracrine stimulation of the pathway than genetic mutations. Analysis of the expression levels indeed showed significant differences in the expression of Wnt pathway components between the different breast cancer cell lines. In accordance with this finding, assessment of autocrine and paracrine pathway activation revealed a set of Wnt-responsive cell lines. Treatment with different Wnt pathway inhibitors or knockdown of b-catenin in these cell lines resulted in decreased cell proliferation, migration and tumorsphere formation, indicating that some breast cancers could benefit from therapeutic inhibition of Wnt signaling. Conclusion: In summary, our Wnt pathway peptide inhibitor could be a promising new drug candidate to be interrogated for the treatment of breast cancer stem cells and a defined subset of breast cancer tumors. Disclosure of Interest: All contributors are employees of Nexigen GmbH. A. Friebe and J. Vollmer additionally are shareholders of Nexigen GmbH. P053 Serum HER2 extracellular domain before surgery compared with HER2 in breast cancer J. Zidan1 *, R. Mzalbat2 , A. Sharabi2 . 1 Oncology, Oncology Institute. Ziv Medical Center, Safed, Israel, 2 Ziv Medical Center, Safed, Israel Goals: Human epidermal growth factor receptor 2 (HER2) is an important prognostic and predictive factor in breast cancer (BC). The importance HER2 extracellular domain (ECD) in serum is not yet determined. The aim of this study was to explore the correlation between serum ECD and tissue HER2 expression, clinical and pathological features in primary BC. Methods: In this prospective study only patients with stage I–III BC were included. Serum ECD levels were measured by ADVIA Centaur automated assays before surgical resection of the tumor. Serum ECD >15 ng/ml was considered to be positive. Results: Eighty patients with breast tumors were included. Stage I–III BC was diagnosed in 64 patients, Ductal carcinoma in situ in 9 and
14th St.Gallen International Breast Cancer Conference / The Breast 24S1 (2015) S26–S86
benign tumors in 7 patients. HER2 overexpression was observed in 8 of 64 patients (16.4%). Mean value of serum ECD was 10.9 ng/ml (range: 6.7 to 21.5). Four (6.2%) of the 64 patients had high ECD levels and in 60 (93.8%) patients lower levels of ECD were found. No significant relationship was found between ECD levels and tissue HER2 overexpression. ECD was higher in women aged >40 than in women <40. ECD was higher in Arab than in Jewish patients. No significant relation was found between ECD and all clinical and pathological features. Conclusion: The sensitivity of HER2 ECD for the diagnosis of HER2 overexpression in primary breast cancer is poor. No significant correlation was found between ECD levels and tissue HER2 expression, clinical and pathological characteristics of primary BC. Disclosure of Interest: No significant relationships. P054 Embryonic stem cells and BR CA risk & prognosis in a North Indian cohort: multi-analytical study G. Agarwal1 *, S. Tulsiyan2 , P. Lal3 , B. Mittal2 . 1 Endocrine & Breast Surgery, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India, 2 Genetics, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India, 3 Radiation Oncology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India Goals: Variations in surface biomarkers (CD44) and regulatory genes (OCT4, SOX2, NANOG, LIN28) of Embryonic Stem Cells (ESCs) may lead to breast cancer cell growth, differentiation and metastasis. We studied the role of ESCs gene polymorphisms in breast cancer risk and prognosis using multi-analytical strategies in a North Indian breast cancer patient cohort and healthy controls. Methods: Polymorphisms in CD44 (rs353639, rs13347), OCT4 (rs3130932), NANOG (rs11055786), LIN28 (rs4274112) and SOX2 (rs11915160) genes were evaluated in 258 females North Indian breast cancer patients and 205 healthy controls. Response to neoadjuvant chemotherapy (NACT) was evaluated per RECIST criteria in 114 patients. Taqman allelic discrimination assays were used for genotyping. Statistical analysis was performed using SPSS and GMDR. Online browser F-SNP was used for in-silico analysis for prediction of functional effects. Results: Comparing the OCT4 gene polymorphism in breast cancer patients and healthy controls, a protective effect of genotypes AC [P = 0.016, OR = 0.64 (0.44–0.92)] and AC+CC [P = 0.019, OR = 0.62 (0.42–0.92)] was apparent. In SOX2 rs11915160, AC [P = 0.017, OR = 2.93 (1.21–7.09)] and AC+CC [P = 0.011, OR = 3.09 (1.28–7.43)] genotypes were found associated with breast cancer risk. No association of CD44, NANOG, and LIN28 gene polymorphisms were found with breast cancer risk. For CD44 rs353639 polymorphism, AC+CC genotype [P = 0.017, OR = 4.29 (1.30–14.11)] and C allele [P = 0.025, OR = 3.34 (1.16–9.59)] were significantly correlated with tumour size. However, no association was seen with CD44 rs13347. Significant association of AG+GG genotype [P = 0.021, OR = 6.08 (1.83–20.15)] and G allele [P = 0.021, OR = 3.07 (1.21–7.77)] of LIN28 rs4274112 polymorphism were seen with lymph node metastases. For OCT4 rs3130932, significant association of allele C was seen with hormone receptor negative status [Sr = 0.021, OR = 0.51 (0.29– 0.90)]. None of the studied polymorphisms individually were found correlated with response to NACT. On GMDR analysis, we found combination of SNPs OCT4 rs3130932, NANOG rs11055786 to be the best interaction model for predicting breast cancer risk [CVC = 8/10] and OCT4 rs3130932, LIN28 rs4274112 for response to NACT [CVC = 9/10]. In-silico analysis using F-SNP, showed altered transcriptional regulation for rs353639, rs13347, rs11915160 and rs4274112 polymorphism. However, rs3130932 showed change in protein coding mechanism and rs11055786 in splicing regulation.
S45
Conclusion: Combination of genetic variants in ESC genes may have influence in both breast cancer susceptibility and poor response to NACT in north Indian breast cancer patients. Disclosure of Interest: No significant relationships. P055 Clinical dilemma of contradictory HER2 results in breast cancer resolved by microarrays M.J. Kotze1 *, E. Murray2 , H.K. Lukhoff1 , K. Grant1 . 1 Pathology, Stellenbosch University, Cape Town, South Africa, 2 Private Oncology Practice, Cape Town, South Africa Goals: The study was performed at the interface between the laboratory and oncology practice in an attempt to address the clinical dilemma presented by equivocal and contradictory results for human epidermal growth factor receptor-2 (HER2) status frequently obtained in patients with early-stage breast cancer. The aim was to evaluate whether microarray gene profiling might provide additional benefit under these circumstances. The high false-negative rate of HER2 status reported with use of Oncotype DX cautions against the use of reverse transcriptase polymerase chain reaction (RT-PCR) technology for selection of breast cancer patients for HER2 targeted treatment. Methods: Microarray analysis was performed using RNA extracted from 41 fresh tumour biopsies and 119 formalin-fixed paraffin embedded (FFPE) tissue specimens. Three lines of genomic information based on MammaPrint, TargetPrint and BluePrint were obtained over and above standard immunohistochemistry/ fluorescence in situ hybridisation (IHC/FISH) to help guide treatment decisions. Results: We demonstrated 100% agreement of HER2 status following IHC/FISH reflex testing in all five discordant cases identified (Grant et al. in press). In a further patient suffering from idiopathic thrombocytopenic purpura and who presented with contradictory IHC/FISH findings, the following results were obtained that support a low risk for distant recurrence: 1) MammaPrint (70 genes): Low-risk profile, despite HER2 copy number of 6.5 compatible with HER2positive status according to the ASCO/CAP guidelines. 2) TargetPrint (3 genes): HER2-negative, in accordance with the HER2/CEP17 ratio of 1.5 considered compatible with HER2-negative status according to local guidelines for HER2 assessment (modified in November 2014 partly as a result of this comparative study) 3) BluePrint (80genes): Luminal A subtype, which is associated with HER2-negative status (excluded the HER2-enriched and Luminal B subtypes mostly associated with HER2-positive status). Conclusion: Determination of HER2 status across three assay platforms facilitated improved quality assurance and led to a higher level of confidence on which treatment decisions were based. Equivocal and contradictory IHC/FISH results and borderline HER2 cases have become important considerations when either Oncotype DX or the MammaPrint microarray is requested in South African patients. Breast cancer patients with rare categories of HER2 status not adequately covered by existing guidelines may also benefit from objective microarray gene profiling. Disclosure of Interest: Prof MJ Kotze is a shareholder and director of Gknowmix (Pty) Ltd.