Qualification of a multiplexed tissue imaging assay and detection of novel patterns of HER2 heterogeneity in breast cancer

Emerging data suggests that HER2 intratumoral heterogeneity (ITH) is associated with therapy resistance, highlighting the need for new strategies to assess HER2 ITH. A promising approach is leveraging multiplexed tissue analysis techniques such as cyclic immunofluorescence (CyCIF), which enable visualization and quantification of 10-60 antigens at single-cell resolution from individual tissue sections. In this study, we qualified a breast cancer-specific antibody panel, including HER2, ER, and PR, for multiplexed tissue imaging. We then compared the performance of these antibodies against established clinical standards using pixel-, cell- and tissue-level analyses, utilizing 866 tissue cores (representing 294 patients). To ensure reliability, the CyCIF antibodies were qualified against HER2 immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) data from the same samples. Our findings demonstrate the successful qualification of a breast cancer antibody panel for CyCIF, showing high concordance with established clinical antibodies. Subsequently, we employed the qualified antibodies, along with antibodies for CD45, CD68, PD-L1, p53, Ki67, pRB, and AR, to characterize 567 HER2+ invasive breast cancer samples from 189 patients. Through single-cell analysis, we identified four distinct cell clusters within HER2+ breast cancer exhibiting heterogeneous HER2 expression. Furthermore, these clusters displayed variations in ER, PR, p53, AR, and PD-L1 expression. To quantify the extent of heterogeneity, we calculated heterogeneity scores based on the diversity among these clusters. Our analysis revealed expression patterns that are relevant to breast cancer biology, with correlations to HER2 ITH and potential relevance to clinical outcomes.

Nivolumab in combination with cabozantinib for metastatic triple-negative breast cancer: a phase II and biomarker study

This single-arm phase II study investigated the efficacy and safety of cabozantinib combined with nivolumab in metastatic triple-negative breast cancer (mTNBC). The primary endpoint was objective response rate (ORR) by RECIST 1.1. Biopsies at baseline and after cycle 1 were analyzed for tumor-infiltrating lymphocytes (TILs), PD-L1, and whole-exome and transcriptome sequencing. Only 1/18 patients achieved a partial response (ORR 6%), and the trial was stopped early. Toxicity led to cabozantinib dose reduction in 50% of patients. One patient had a PD-L1-positive tumor, and three patients had TILs > 10%. The responding patient had a PD-L1-negative tumor with low tumor mutational burden but high TILs and enriched immune gene expression. High pretreatment levels of plasma immunosuppressive cytokines, chemokines, and immune checkpoint molecules were associated with rapid progression. Although this study did not meet its primary endpoint, immunostaining, genomic, and proteomic studies indicated a high degree of tumor immunosuppression in this mTNBC cohort.

The Immunology of Hormone Receptor Positive Breast Cancer

Immune checkpoint blockade (ICB) has revolutionized the treatment of cancer patients. The main focus of ICB has been on reinvigorating the adaptive immune response, namely, activating cytotoxic T cells. ICB has demonstrated only modest benefit against advanced breast cancer, as breast tumors typically establish an immune suppressive tumor microenvironment (TME). Triple-negative breast cancer (TNBC) is associated with infiltration of tumor infiltrating lymphocytes (TILs) and patients with TNBC have shown clinical responses to ICB. In contrast, hormone receptor positive (HR+) breast cancer is characterized by low TIL infiltration and minimal response to ICB. Here we review how HR+ breast tumors establish a TME devoid of TILs, have low HLA class I expression, and recruit immune cells, other than T cells, which impact response to therapy. In addition, we review emerging technologies that have been employed to characterize components of the TME to reveal that tumor associated macrophages (TAMs) are abundant in HR+ cancer, are highly immune-suppressive, associated with tumor progression, chemotherapy and ICB-resistance, metastasis and poor survival. We reveal novel therapeutic targets and possible combinations with ICB to enhance anti-tumor immune responses, which may have great potential in HR+ breast cancer.

Comparison of Breast Cancer Staging Systems After Neoadjuvant Chemotherapy

BACKGROUND

No consensus exists for optimal staging following neoadjuvant chemotherapy (NAC). We compared the performance of the American Joint Committee on Cancer (AJCC) pathologic prognostic staging system, Residual Cancer Burden (RCB) Index, and the Neo-Bioscore in breast cancer patients after NAC.

METHODS

Patients with stage I-III breast cancer who received NAC at Dana-Farber Cancer Institute from 2004 to 2014 were identified. Kaplan-Meier curves were used to estimate disease-free survival (DFS) and overall survival (OS), and model fits were compared by receiver operator characteristic (ROC) curve using the c-statistic and DeLong's test.

RESULTS

Overall, 802 patients with a median age of 48 years received NAC. Most patients presented with cT2 (n = 470, 58.6%) and cN1 (n = 422, 52.6%) disease. The subtype was estrogen receptor (ER)- and/or progesterone receptor (PR)-positive/human epidermal growth factor receptor 2 (HER2)-negative in 296 (36.9%) patients, HER2-positive in 261 (32.5%) patients, and triple-negative in 245 (30.5%) patients. Median follow-up was 79.5 months. There were 174 recurrences (30 local, 25 regional, 145 distant), with 676 (76.8%) patients alive at last follow-up. AJCC pathologic prognostic staging and RCB had better discrimination for estimated 7-year DFS and OS compared with the Neo-Bioscore. The ROC c-statistics for DFS model fit were similar for AJCC pathologic prognostic stage (0.72) and RCB (0.71, p = non-significant); both had improved model fit versus the Neo-Bioscore (0.65, p < 0.01). The c-statistics for OS were 0.74, 0.71, and 0.70 for AJCC pathologic prognostic stage, RCB, and Neo-Bioscore, respectively (p = non-significant).

CONCLUSIONS

These results validate the ability of these staging systems to stratify survival outcomes in NAC patients, with best discrimination achieved using AJCC pathologic prognostic stage or RCB.

Clinico-pathologic predictors of patterns of residual disease following neoadjuvant chemotherapy for breast cancer

Among breast cancer patients treated with neoadjuvant chemotherapy (NAC) who do not experience a pathologic complete response (pCR), the pattern of residual disease in the breast varies. Pre-treatment clinico-pathologic features that predict the pattern of residual tumor are not well established. To investigate this issue, we performed a detailed review of histologic sections of the post-treatment surgical specimens for 665 patients with stage I-III breast cancer treated with NAC followed by surgery from 2004 to 2014 and for whom slides of the post-NAC surgical specimen were available for review. This included 242 (36.4%) patients with hormone receptor (HR)+/HER2- cancers, 216 (32.5%) with HER2+ tumors, and 207 (31.1%) with triple negative breast cancer (TNBC). Slide review was blinded to pre-treatment clinico-pathologic features. pCR was achieved in 7.9%, 37.0%, and 37.7%, of HR+/HER2- cancers, HER2+ cancers, and TNBC respectively (p < 0.001). Among 389 patients with residual invasive cancer in whom the pattern of residual disease could be assessed, 287 (73.8%) had a scattered pattern and 102 (26.2%) had a circumscribed pattern. In both univariate and multivariate analyses, there was a significant association between tumor subtype and pattern of response. Among patients with HR+/HER2- tumors, 89.4% had a scattered pattern and only 10.6% had a circumscribed pattern. In contrast, among those with TNBC 52.8% had a circumscribed pattern and 47.2% had a scattered pattern (p < 0.001). In addition to subtype, histologic grade and tumor size at presentation were also significantly related to the pattern of residual disease in multivariate analysis, with lower grade and larger size each associated with a scattered response pattern (p = 0.002 and p = 0.01, respectively). A better understanding of the relationship between pre-treatment clinico-pathologic features of the tumor and pattern of residual disease may be of value for helping to guide post-chemotherapy surgical management.

Abstract PS6-07: Comparison of breast cancer staging models in patients after neoadjuvant chemotherapy

Background: Neoadjuvant chemotherapy (NAC) is commonly utilized for breast cancer, however no consensus exists on the best way to stage these patients following treatment. Importantly, the American Joint Commission on Cancer (AJCC) 8th edition staging system did not specifically address staging after NAC. However, previous work by our group has shown that the pathologic prognostic stage does stratify patients with respect to outcomes. Our objective was to compare performance of the AJCC pathologic prognostic staging system to a second staging model, the Residual Cancer Burden (RCB) Index which takes into account residual tumor size, cellularity, lymph node status and size of any lymph node metastases.

Methods: A retrospective review identified patients with stage I-III invasive breast cancer treated with NAC from 2004-2014 at Dana-Farber Cancer Institute. Patients were excluded if they did not have RCB reported on final pathology. Disease-free survival (DFS) was defined as any recurrence or death from any cause, and overall survival (OS) as death from any cause. DFS and OS were calculated using the Kaplan-Meier method for each staging model. Receiver operator characteristic (ROC) curves were used to assess model fit using the c-statistic and the Hanley method to compare c-statistics.

Results: A total of 802 patients underwent NAC for stage I-III breast cancer. The median age was 48 years (range 22-86). Most patients presented with cT2 (n=470, 58.6%) or cT3 (n=188, 23.4%) and cN1 (n=422, 52.6%) disease. The majority (n=563, 70.2%) presented with grade 3 disease. In terms of subtype, 296 (36.9%) patients had hormone receptor-positive, HER2 negative, 261 (32.5%) HER2+, and 245 (30.5%) triple negative disease. Median follow up was 79.5 months (range 4-169). There were 176 recurrences including 32 local, 25 regional, and 145 distant recurrences. 676 (76.8%) patients were alive at last follow-up. The Table depicts the 7-year DFS and OS estimates for each of the staging models. The ROC c-statistics for DFS model fit were statistically similar, 0.72 for AJCC pathologic prognostic stage and 0.71 for RCB (p=NS). The c-statistics for OS were 0.74 and 0.71 respectively (p=NS).

Conclusions: Our results provide additional external validation of the AJCC pathologic prognostic stage and RCB’s ability to stratify patients after NAC with respect to survival outcomes. These data can be used to inform subsequent revisions of the AJCC breast cancer staging system.

Estimated 7-year DFS and OS in Potential Staging Models for Breast Cancer Patients after NAC (n=802)7yr-DFS7yr-OSPathologic Prognostic StageStage 0 (n=228)92.9%94.8%Stage IA (n=193)81.7%90.2%Stage IB (n=173)74.5%86.6%Stage IIA (n=105)62.2%71.5%Stage IIB (n=11)70.2%57.3%Stage IIIA (n=40)62.2%75.4%Stage IIIB (n=27)56.7%83.0%Stage IIIC (n=25)27.8%28.2%C-statistic (95% CI)0.72 (0.68-0.76)0.74 (0.69-0.79)RCB0 (n=226)93.5%94.8%I (n=118)83.0%90.0%II (n=278)75.9%85.0%III (n=180)55.1%69.9%C-statistic (95% CI)0.71 (0.67-0.75)0.71 (0.66-0.75)

Citation Format: Olga Kantor, Alison Laws, Ricardo G Pastorello, Stephanie Wong, Tanujit Dey, Stuart Schnitt, Tari A King, Elizabeth A Mittendorf. Comparison of breast cancer staging models in patients after neoadjuvant chemotherapy [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS6-07.

Abstract PS18-02: Highly multiplexed tissue-based cyclic immunofluorescence (t-CyCIF) for precision oncology identifies novel patterns of HER2 heterogeneity in breast cancer

Background

Immunohistochemical (IHC) evaluation has shown that human epidermal growth factor receptor 2 (HER2) may not be expressed homogeneously among all cancer cells within a given tumor. The clinical significance of intratumoral HER2 heterogeneity is unclear. Exploration of tumor heterogeneity is facilitated by tissue imaging technologies such as t-CyCIF, a highly multiplexed immunofluorescence microscopy technique that permits visualization of up to 60 antigens and analysis on a single cell level from formalin-fixed, paraffin-embedded tissue. To utilize t-CyCIF for the evaluation of breast tumors, this study was undertaken to: 1) validate antibodies to be used against the clinically relevant markers HER2, estrogen receptor (ER) and progesterone receptor (PR), and 2) use these antibodies along with other validated antibodies to define the tumor microenvironment (TME) to interrogate breast tumors at a single cell level.

Methods

T-CyCIF is an iterative whole-slide imaging process, in which successive four-channel images, each involving different antibodies, are collected from the same sample and then merged to generate a high-dimensional representation used for visualization and analysis. In phase one of this study, 948 tissue cores (representing 295 patients in triplicate) were used to validate HER2, ER, and PR antibodies against a single antibody commonly used in clinical practice as a reference. Analyses were performed at the level of tissue cores, cells and pixels. Inter-assay analyses were performed comparing: t-CyCIF vs. IHC, the latter assessed by digital pathology and two pathologists; and also, t-CyCIF vs. fluorescence in situ hybridization (FISH) for HER2. In the second phase, following selection of validated HER2, ER and PR antibodies, expression of CD45, CD68, PD-L1, p53, Ki67, pRB and the androgen receptor (AR) were evaluated at a single cell level in 312 HER2+ invasive breast cancer samples, representing 104 patients, to better understand the TME, cancer cell heterogeneity and the cell identities/states present in breast carcinomas.

Results

In the first phase of the study, 13 different ER, PR or HER2 antibodies were analyzed. The pixel-to-pixel evaluation, which evaluates concordance in staining, resulted in r scores of 0.86 (ER; Pearson correlation), 0.93 (PR) and 0.94 (HER2) and correlation scores in single-cell comparisons ranged from 0.76 to 0.81. Correlation scores on the tissue core level were high in the inter-assay analyses, i.e. t-CyCIF vs. IHC (e.g. r scores up to 0.87 and 0.91 for ER and HER2, respectively, on t-CyCIF vs. Aperio; and 0.85 to 0.94 by pathology review) and t-CyCIF vs. HER2 FISH (r scores up to 0.71). This resulted in validated fluorophore-conjugated antibody panels for use in t-CyCIF that correspond well to established standards. In the second phase, single cell analysis of HER2+ breast cancer was performed. Cancer cells were defined as keratin positive and using t-Distributed Stochastic Neighbor Embedding (t-SNE) seven cancer cell clusters were identified including two HER2hi clusters differing in ER, p53, AR and PD-L1 expression, two HER2lo clusters differing in PR, Ki67, pRB, p53 and AR and three HER2neg clusters differing in PR, Ki67, ER, PD-L1 and AR. Heterogeneity scores were calculated based on diversity among clusters.

Conclusion

This study is the first to evaluate the performance of breast cancer-specific antibodies in a highly multiplexed imaging platform such as t-CyCIF. Using the validated antibody panel, we uncovered patterns of expression of markers relevant to breast cancer biology that correlate with HER2 high, low and negative states. Ongoing studies are looking at correlations between HER2 heterogeneity, responses to therapy and clinical outcomes.

Citation Format: Jennifer L Guerriero, Jia-Ren Lin, Ricardo G Pastorello, Ziming Du, Shaolin Mei, Krishan Taneja, Stuart J Schnitt, Deborah A Dillon, Peter K Sorger, Sandro Santagata, Elizabeth A Mittendorf. Highly multiplexed tissue-based cyclic immunofluorescence (t-CyCIF) for precision oncology identifies novel patterns of HER2 heterogeneity in breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS18-02.

Experience on the use of The Paris System for Reporting Urinary Cytopathology: review of the published literature

INTRODUCTION

The Paris System for Reporting Urinary Cytology (TPS) was first published in 2016 with clear objectives to standardize cytologic diagnostic criteria and provide uniform reporting, in order to improve patient stratification and associated clinical management. The aim of this paper is to evaluate the performance of TPS and review the literature published since TPS was introduced.

MATERIALS AND METHODS

Original articles focusing on the utilization and performance of TPS in urinary cytology specimens were identified using PubMed for publications from January 2016 to July 2020, using the keywords "Paris System", "urine cytology", and "urinary cytology".

RESULTS

Twenty-three relevant articles in the literature regarding the use of TPS were included in the review from a total of 30,802 urine cytology specimens, of which 21,485 (69.8%) had available diagnoses. Distribution of cases among categories ranged from 50.5% to 95.3% for negative for high-grade urothelial carcinoma (NHGUC), 1.2% to 23% for atypical urothelial cells (AUC), 0.2% to 6.6% for suspicious for high-grade urothelial carcinomas (SHGUC), and 2.2% to 14.1% for high-grade urothelial carcinomas (HGUC). The calculated risk of high-grade malignancy (ROHM) ranged from 8.7% to 36.8% for NHGUC, 12.3% to 60.9%% for AUC, 33.3% to 100% for SHGUC, and 58.8% to 100% for HGUC. Mean ROHM weighted by sample size was calculated at 15.7% (±7.8%), 38.5% (±14.3%), 76.2% (±17.2%), and 88.8% (±12.7%) for NHGUC, AUC, SHGUC, and HGUC, respectively. Reported sensitivity of TPS ranged from 40% to 84.7%, specificity from 73% to 100%, PPV from 62.3% to 100%, and NPV from 46% to 90%.

CONCLUSIONS

The application of TPS in the selected series has improved the screening and surveillance potential of urine cytology, while reducing high rates of indeterminate diagnoses, improving sensitivity and providing proper risk stratification for patients.

Suspicious for Malignancy Diagnoses on Pleural Effusion Cytology

OBJECTIVES

A definitive diagnosis of malignancy may not be possible in pleural effusions. We report our experience with the diagnosis of suspicious for malignancy (SFM) in pleural effusion.

METHODS

A search for pleural effusions diagnosed as SFM (2008-2018) was performed. Patient records and pathology reports were reviewed. Specimens were subdivided into groups depending on volume (<75, 75-400, >400 mL). Diagnoses of malignant pleural effusion (MPE) served as controls.

RESULTS

We identified 90 patients, with a mean age of 60.6 years. Diagnoses included suspicious for involvement by carcinoma/adenocarcinoma in 64.4%, leukemia/lymphoma in 15.6%, melanoma in 2.2%, sarcoma in 3.3%, germ cell tumor in 1.1%, and not otherwise specified in 13.3%. Immunostains were performed in 47.8% and considered inconclusive in 24%. Average sample volume was 419 mL. There was a statistically significant difference between the SFM vs MPE groups for volumes greater than 75 mL (P = .001, χ 2 test), with SFM having increased proportion of volumes  greater than 400 mL, compared with the MPE group. There was no statistically significant difference in mean overall survival when the groups were compared (P = .49).

CONCLUSIONS

Samples with low cellularity, scant cell blocks, and inconclusive immunostains may contribute to a suspicious category diagnosis in pleural effusions.

The impact of pattern of tumor response and other post-treatment histologic features on local recurrence in patients treated with neoadjuvant chemotherapy and breast conservation

581

Background: Residual disease after neoadjuvant chemotherapy (NAC) is a poor prognostic factor. The relationship between the pattern of tumor response and other post-treatment histologic features on local recurrence (LR) is not well studied. Methods: We identified 380 patients (pts) treated with NAC, breast-conserving surgery and radiation from 2002-2014. Pts with available surgical slides underwent detailed pathology review. Pathologic complete response (pCR) was defined as no invasive or in situ disease in the breast or axilla. Pattern of tumor response was defined as: none, scattered, or concentric. The degree of treatment effect was categorized as: absent, mild or marked. Univariate (UVA) and multivariate analyses (MVA) were performed to identify factors associated with LR. Results: 243 (64%) cases had complete slides available and formed the study cohort. 76 (31%) were ER+/HER2-, 90 (38%) ER-/HER2- and 77 (31%) HER2+. 98% of HER2+ pts received neoadjuvant trastuzumab; 89% of ER+ pts received adjuvant endocrine therapy. At median follow-up of 75 months, 10/243 (4.1%) pts had LR and 5-yr LR-free survival was 95.7%. LR occurred in 1/76 (1.3%) pts with breast pCR, 1/19 (5.2%) with residual DCIS, and 8/148 (5.4%) with residual invasive disease; including 6/78 (7.7%) with scattered tumor response, 2/46 (4.3%) with concentric response and 0/24 with no response. On UVA, age (OR < 50 vs ≥50 5.9, p = 0.03) and residual DCIS with comedonecrosis (OR 8.2, p < 0.01) were significantly associated with LR. Presence of tumor bed at the margin (OR 4.6, p = 0.06) approached significance. The odds of LR were higher with scattered regression (OR 1.83 vs. concentric, p = 0.47) and lower with breast pCR (OR 0.23, p = 0.17), but these results were not statistically significant. Multicentric disease, receptor status, ypT, ypN, RCB score, degree of treatment effect, high-grade residual invasive disease, margin status of residual disease and lymphovascular invasion were not associated with LR (all p > 0.05). Age (OR < 50 vs ≥50 7.4, p = 0.04) and residual DCIS with comedonecrosis (OR 7.5, p = 0.02) remained significant on MVA. Conclusions: With modern systemic therapy, LR rates after NAC, breast-conserving surgery and radiation are low, with less than 5% of patients experiencing a LR after a median follow-up of over 6 years. Young age and residual DCIS with comedonecrosis were associated with LR, but not pattern of tumor response.

Application of the International System for Reporting Serous Fluid Cytopathology (ISRSFC) on Reporting Pericardial Effusion Cytology

INTRODUCTION

The International System for Reporting Serous Fluid Cytopathology (ISRSFC) has recently been announced. Pericardial effusion (PE) is a clinical manifestation of a large variety of both neoplastic and non-neoplastic conditions. Herein, we have applied the ISRSFC on reporting PE cytopathology and report our experience in a large academic institution.

METHOD AND MATERIALS

After the Institutional Research Board approval, the electronic pathology database of a large academic institution was queried for PEs collected from January 2014 to January 2019. The diagnosis, patient demographics, and specimen volume were recorded for each case. The ISRSFC was applied and the cases were divided into 5 categories: nondiagnostic (ND), negative for malignancy (NFM), atypia of uncertain significance (AUS), suspicious for malignancy (SFM), and malignant (MAL). Each category was evaluated separately.

RESULTS

A total of 299 cases were identified, 162 females and 137 males. The age of the subjects ranged from less than a year to 89 years (average 51.25 years). The volume ranged from 3 to 1,700 mL (average 298 mL). There were 252 NFM (84.3%), 13 AUS (4.3%), 4 SFM (1.3%), and 30 MAL (10%) cases. Metastatic lung cancer followed by metastatic breast cancer were the most common malignancies involving pericardial fluid (PF). No cases were diagnosed as ND. However, no mesothelial cells were seen in 97 specimens (38% of the negative cases). None of these patients developed malignant PE in at least 6 months of follow-up.

CONCLUSION

The ISRSFC is a user-friendly reporting system which is easily applicable on serous fluid including PF. The vast majority of PEs was benign (84.3%). Our study shows that the presence of mesothelial cells is not necessary for specimen adequacy in serous effusions as no mesothelial cells were identified in 38% of the negative cases. Metastatic lung carcinoma was the most common diagnosis of malignant effusions.

Number of mesothelial cells as a measure of adequacy criteria for pleural effusions: A multi-institutional study

BACKGROUND

The development of a terminology system is essential to allow uniformity in reporting serous fluid specimens. An important topic to cover is the issue of specimen adequacy. In the present study, we aimed to evaluate whether there is a correlation between number of mesothelial cells and overall improved sensitivity and adequacy control of tests.

METHODS

Cases of negative pleural fluids with concomitant positive pleural biopsies were selected from two referral institutions, with observation of the number of mesothelial cells in 10 high-power fields, comparing the results with a control group (cases with negative biopsies, ie, true negatives). Comparisons were conducted using the nonparametric Mann-Whitney U test. Data were analysed for sensitivity and specificity derived from the receiver operating characteristics curve. For the choice of an optimal cut-off of mesothelial cells, receiver operating curve analysis was constructed and the Youden index was calculated.

RESULTS

A total of 112 pleural effusions with paired pleural biopsies were studied. There was no difference in distributions of the number of mesothelial cells between cases with a positive biopsy (false negatives) and the control group (median = 39 vs median = 30, respectively, P-value = .974). However, simple logistic regression found a cut-off of 750 cells per 10 high-power fields as an optimal number for improved sensitivity (72.7%), with fair discriminatory power.

CONCLUSIONS

Enumeration of mesothelial cells may improve the sensitivity of the cytological diagnosis of malignant pleural effusion, serving as an internal quality control for the test's overall accuracy.

Abstract P5-02-03: Highly multiplexed tissue-based cyclic immunofluorescence in breast cancer for precision oncology

Background: Tissue-based cyclic immunofluorescence (t-CyCIF) is a recently described technique for highly multiplexed immunofluorescence microscopy of formalin-fixed, paraffin-embedded (FFPE) specimens. Via an iterative process, successive four-channel images are collected from the same sample and then registered to each other to generate a high-dimensional representation that is used for visualization and analysis. This technique can be used to capture up to 60 different antigens on a single FFPE tumor section and permits quantification of cell lineage and state markers, intracellular signaling proteins, drug targets and immune cell antigens, thereby promoting biomarker discovery efforts that are fundamental to precision oncology. As with most technologies that utilize immunostaining, proper antibody validation is key to reliable performance. In this study we used t-CyCIF to evaluate multiple antibodies directed against proteins commonly used to characterize breast carcinomas and their associated microenvironment. Our goal was to validate these antibodies on the t-CyCIF platform prior to the more widespread use of this technology to propel novel discoveries on breast cancer initiation, progression and treatment.

Methods: To choose the optimal antibody candidate for each biomarker in t-CyCIF, we compared multiple fluorophore-conjugated antibodies for each of the following three proteins routinely evaluated in breast carcinomas: estrogen receptor (ER), progesterone receptor (PR) and HER2. For each of these, a single antibody commonly used in clinical practice was used as a reference. Analyses were performed at the level of pixels, cells and tissue cores. In addition, inter-assay analyses were performed comparing: (1) t-CyCIF vs. immunohistochemistry (IHC), the latter assessed both by digital pathology and by two independent pathologists; and (2) t-CyCIF vs. fluorescence in situ hybridization (FISH) for HER2. Following validation of these antibodies, we evaluated the expression of CD45, CD68, PD-L1, p53, Ki67 and androgen receptor along with ER, PR and HER2, to better understand both the tumor microenvironment and the cell identities/states in breast carcinomas.

Results: A total of 948 tissue cores were included in the study. In the first phase, 13 different antibodies were analyzed: three raised against ER and five each against PR and HER2. The pixel-to-pixel evaluation resulted in r scores using Pearson correlation equal to 0.86 for both ER markers tested; ranging from 0.88 to 0.93 for PR; and from 0.56 to 0.94 for HER2. The correlation scores in single-cell comparisons ranged from 0.76 to 0.88 for ER, 0.54 to 0.81 for PR, and from 0.56 to 0.76 for HER2. Comparisons were then performed at the tissue core level. In light of the data generated through these multiple levels of analyses, we identified fluorophore-conjugated candidates for use in t-CyCIF. Correlation scores on the tissue core level were high in the inter-assay analyses, i.e. t-CyCIF vs. IHC (e.g. r scores up to 0.91 for HER2 on t-CyCIF vs. IHC) and t-CyCIF vs. HER2 FISH (r scores up to 0.71). In the second phase, we characterized the tumor microenvironment and cell identities present in 260 breast carcinomas. With a qualified panel of antibodies, we performed single-cell analyses of 589,343 cells and identified unexpected patterns of PD-L1 expression in distinct populations of tumor cells.

Conclusion: This study is the first to evaluate the performance of breast cancer-specific antibodies in a highly multiplexed imaging platform such as t-CyCIF. This work demonstrates a step-by-step approach for qualifying reagents to be used in a multiplexed, spatially resolved tissue imaging modality. This validation study will facilitate the use of t-CyCIF for additional studies in breast cancer to evaluate both tumor elements and components of the microenvironment.

Citation Format: Ricardo G Pastorello, Jia-Ren Lin, Ziming Du, Shaolin Mei, Krishan Taneja, Deborah A Dillon, Stuart J Schnitt, Peter K Sorger, Elizabeth A Mittendorf, Sandro Santagata, Jennifer L Guerriero. Highly multiplexed tissue-based cyclic immunofluorescence in breast cancer for precision oncology [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P5-02-03.

A Phase II Study of Pembrolizumab in Combination With Palliative Radiotherapy for Hormone Receptor-positive Metastatic Breast Cancer

BACKGROUND

The purpose of this study was to investigate whether combining pembrolizumab with palliative radiation therapy (RT) improves outcomes in patients with hormone receptor-positive (HR⁺) metastatic breast cancer (MBC).

PATIENTS AND METHODS

Eligible patients had HR⁺/human epidermal growth factor receptor 2-negative MBC; were candidates for RT to ≥ 1 bone, soft tissue, or lymph node lesion; and had ≥ 1 lesion outside the RT field. Patients received 200 mg pembrolizumab intravenously 2 to 7 days prior to RT and on day 1 of repeating 21-day cycles. RT was delivered to a previously unirradiated area in 5 treatments each of 4 Gy. The primary endpoint was objective response rate. The study used a 2-stage design: 8 women were enrolled into the first stage, and if at least 1 of 8 patients experienced an objective response, 19 more would be enrolled. Secondary endpoints included progression-free survival, overall survival, and safety. Exploratory endpoints included association of overall response rate with programmed death-ligand 1 status and tumor-infiltrating lymphocytes.

RESULTS

Eight patients were enrolled in stage 1. The median age was 59 years, and the median prior lines of chemotherapy for metastatic disease was 2. There were no objective responses, and the study was closed to further accrual. The median progression-free survival was 1.4 months (95% confidence interval, 0.4-2.1 months), and the median overall survival was 2.9 months (95% confidence interval, 0.9-3.6 months). All-cause adverse events occurred in 87.5% of patients, including just 1 grade 3 event (elevation of aspartate aminotransferase).

CONCLUSIONS

RT combined with pembrolizumab did not produce an objective response in patients with heavily pre-treated HR⁺ MBC. Future studies should consider alternative radiation dosing and fractionation in patients with less heavily pre-treated HR⁺ MBC.

Gastric Pouch Mixed Adenoneuroendocrine Carcinoma With a Mixed Adenocarcinoma Component After Roux-en-Y Gastric Bypass

The Roux-en-Y gastric bypass is one of the most common procedures currently performed for surgical treatment of patients with severe obesity. Gastric cancer after bariatric surgery is not common, with most of them arising in the excluded stomach. Gastric mixed adenoneuroendocrine carcinomas are a rare type of stomach malignancy, composed of both adenocarcinoma and neuroendocrine tumor-cell components, with the latter comprising at least 30% of the whole neoplasm. In this article, we report a unique case of a mixed adenoneuroendocrine carcinoma with a mixed adenocarcinoma (tubular and poorly cohesive) component arising in the gastric pouch of a patient who underwent previous Roux-en-Y gastric bypass for glycemic control. Since stomach cancer is not usual in patients who have formerly undergone bariatric surgery and symptoms tend to be nonspecific, such diagnosis is often rendered at an advanced stage. Full assessment of these patients when presenting such vague symptoms is critical for an early cancer diagnosis.