Second-harmonic generation directionality is associated with neoadjuvant chemotherapy response in breast cancer core needle biopsies," J.Abstract. Neoadjuvant chemotherapy (NACT) is routinely administered to subsets of breast cancer patients, including triple negative (TN) or human epidermal growth factor receptor 2-positive (HER2+) cancers. After NACT and subsequent surgical resection, 5% to 30% of patients have no residual invasive carcinoma, termed pathological complete response. Unfortunately, many patients experience little-to-no response after NACT and unnecessarily suffer its side effects. Methods are needed to predict an individual patient's response to NACT. Core needle biopsies, taken before NACT, consist of tumor cells and the surrounding extracellular matrix. We performed second-harmonic generation (SHG) imaging of fibrillar collagen in core needle biopsy sections as a possible predictor of response to NACT. The ratio of forward-to-backward scattering (F/B) SHG was assessed in the "tumor bulk" and "tumor-host interface" in HER2+ and TN core needle biopsy sections. Patient response was classified post-treatment using the Residual Cancer Burden (RCB) score. In HER2+ biopsies, RCB class was associated with F/B derived from the tumor-stromal interface, but not tumor bulk. F/B was not associated with RCB class in TN biopsies. These findings suggest that F/B from needle biopsy sections may be a useful predictor of which patients will respond favorably to NACT, with the potential to help reduce overtreatment. © The Authors.Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

BackgroundClinical assays for the assessment of the human epidermal growth factor receptor-2 (HER2) status in breast cancer include immunohistochemistry (IHC) and in situ hybridization (ISH), both of which have limitations. Recent studies have suggested that a more quantitative approach to the measurement of HER2 protein expression may improve specificity in selecting patients for HER-2 targeted therapy. In the current study, we have used HER2 expression in breast cancer cell lines and clinical samples as a model to explore the potential utility of a novel immunodetection technique, using streptavidin coated Phosphor Integrated Dot fluorescent nanoparticles (PID), which can be quantitatively measured using computer analysis.MethodsThe expression of HER2 protein in cell lines was evaluated with antibody-binding capacity using fluorescence-activated cell sorting (FACS) for comparison with PID measurements to test for correlations with existing quantitative protein analysis methodologies. Various other analytic validation tests were also performed, including accuracy, precision, sensitivity, robustness and reproducibility. A methods comparison study investigated correlations between PID versus IHC and ISH in clinical samples. Lastly, we measured HER2 protein expression using PID in the pretreatment biopsies from 34 HER2-positive carcinomas that had undergone neoadjuvant trastuzumab-based chemotherapy.ResultsIn the analytic validation, PID HER2 measurements showed a strong linear correlation with FACS analysis in breast cell lines, and demonstrated significant correlations with all aspects of precision, sensitivity, robustness and reproducibility. PID also showed strong correlations with conventional HER2 testing methodologies (IHC and ISH). In the neoadjuvant study, patients with a pathologic complete response (pCR) had a significantly higher PID score compared with patients who did not achieve a pCR (p = 0.011), and was significantly correlated to residual cancer burden (RCB) class (p = 0.026, R2 = 0.9975).ConclusionsAnalytic testing of PID showed that it may be a viable testing methodology that could offer advantages over other experimental or conventional biomarker diagnostic methodologies. Our data also suggests that PID quantitation of HER2 protein may offer an improvement over conventional HER2 testing in the selection of patients who will be the most likely to benefit from HER2-targeted therapy. Further studies with a larger cohort are warranted.

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Background: In 2013, the ASCO/CAP consensus panel published updated guidelines for HER2 testing in breast cancer that modified the definition of HER2 amplification by in situ hybridization (ISH), creating five new prognostic categories (group 1: classic amplified, group 2: monosomy, group 3: co-amplified (polysomy), group 4: equivocal, and group 5: classic non-amplified). Patients determined to be ISH amplified, were considered eligible for HER2-directed therapy. Concern over whether patients from non-classic groups 2-4 would benefit from treatment has led to the recent publication of the 2018 HER2 focused update. This update has modified the criteria for interpreting these ISH categories, recommending that the final diagnosis take into consideration a combination of HER2 immunohistochemistry (IHC) and ISH results. With increased emphasis on the HER2 protein assessment, it has prompted us to quantitatively examine HER2 protein expression in the ISH categories, using two different novel technologies. Materials & Methods: A cohort of 170 cases (URMC) and 102 cases (PSHMC) of invasive breast cancers, which had previously undergone HER2 IHC and ISH testing, were selected for this study. Cases were sorted and categorized into the HER2 ISH categories defined by ASCO/CAP. HER2 protein expression was quantitatively measured in the URMC and PSHMC cohorts using a novel immunodetection methodology (streptavidin-coated Phosphor-Integrated Dot (PID) fluorescent nanoparticles), and a novel dual-antibody, proximity-binding immunoassay (HERmark® Breast Cancer Assay, Monogram Biosciences, South San Francisco, California), respectively. HER2 protein expression was compared to the HER2 FISH and IHC results by ASCO/CAP category. Results: Cases in group 1 had a significantly (p < 0.01) higher average PID/cell and HERmark compared to cases in groups 2-5 (Table 1). Cases in groups 2-4 showed lower quantitative levels of HER2 protein expression, similar to the classic non-amplified cases (group 5). Group 1 was further divided into three subgroups (Table 2): Group A - ISH high-level amplified (ratio > 2, HER2 > 6, CEP17 < 2.7), Group B - amplified with elevated CEP17 (ratio > 2, CEP17 > 2.7), and Group C - low-level amplified (ratio > 2, HER2 > 4 and < 6). Group A and B had a significantly (p < 0.01) higher average PID/cell and HERmark compared to Group C. Group C was more comparable to cases in groups 2-5 (Table 1). Conclusion: Our results suggest that quantitative assessment of HER2 protein expression may help to further classify cases for HER2 status for targeted therapy, supporting the 2018 ASCO/CAP recommendation that non-classic ISH results might be resolved by evaluating protein expression. Follow up studies with a larger patient cohort and dual quantitative assessment are warranted. Average PID/cell and HERmark in ASCO category groupsASCO category groupN (URMC)PID/cell (URMC)*N (PSHMC)HERmark (PSHMC)*18888.07761.521011.20N/A32016.0213.84238.5315.95296.3208.3*averageTable 2:Average PID/cell and HERmark in subgroups of Group 1SubgroupN (URMC)PID/cell (URMC)*N (PSHMC)HERmark (PSHMC)*A24157.66465.7B34101.61044.1C3016.9329.8*average Citation Format: Buscaglia B, Turner B, Goda H, Huang W, Leitzel K, Natori T, Nakano Y, Okada H, Sperinde J, Ali S, Vasekar M, D'Aguiar M, McMahon L, Henry J, Lipton A, Hicks D. ASCO/CAP human epidermal growth factor receptor-2 (HER2) in situ hybridization (ISH) categories evaluated by quantitative HER2 protein diagnostic methodologies: A comparative analysis [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-03-02.