Fluorescence imaging for real-time detection of breast cancer tumors using IV injection of indocyanine green with non-conventional imaging: a systematic review of preclinical and clinical studies of perioperative imaging technologies

BACKGROUND

This review summarizes the available data on the effectiveness of indocyanine green fluorescence imaging (ICG-FI) for real-time detection of breast cancer (BC) tumors with perioperative imaging technologies.

METHODS

PubMed and Scopus databases were exhaustively searched for publications on the use of the real-time ICG-FI evaluation of BC tumors with non-conventional breast imaging technologies.

RESULTS

Twenty-three studies were included in this review. ICG-FI has been used for BC tumor identification in 12 orthotopic animal tumor experiences, 4 studies on animal assessment, and for 7 human clinical applications. The BC tumor-to-background ratio (TBR) was 1.1-8.5 in orthotopic tumor models and 1.4-3.9 in animal experiences. The detection of primary human BC tumors varied from 40% to 100%. The mean TBR reported for human BC varied from 2.1 to 3.7. In two studies evaluating BC surgical margins, good sensitivity (93.3% and 100%) and specificity (60% and 96%) have been reported, with a negative predictive value of ICG-FI to predict margin involvement intraoperatively of 100% in one study.

CONCLUSIONS

The use of ICG-FI as a guiding tool for the real-time identification of BC tumors and for the assessment of tumor boundaries is promising. There is great variability between the studies with regard to timing and dose. Further evidence is needed to assess whether ICG-guided BC surgery may be implemented as a standard of care.

Image-based multiplex immune profiling of cancer tissues: translational implications. A report of the International Immuno-oncology Biomarker Working Group on Breast Cancer

Recent advances in the field of immuno-oncology have brought transformative changes in the management of cancer patients. The immune profile of tumours has been found to have key value in predicting disease prognosis and treatment response in various cancers. Multiplex immunohistochemistry and immunofluorescence have emerged as potent tools for the simultaneous detection of multiple protein biomarkers in a single tissue section, thereby expanding opportunities for molecular and immune profiling while preserving tissue samples. By establishing the phenotype of individual tumour cells when distributed within a mixed cell population, the identification of clinically relevant biomarkers with high-throughput multiplex immunophenotyping of tumour samples has great potential to guide appropriate treatment choices. Moreover, the emergence of novel multi-marker imaging approaches can now provide unprecedented insights into the tumour microenvironment, including the potential interplay between various cell types. However, there are significant challenges to widespread integration of these technologies in daily research and clinical practice. This review addresses the challenges and potential solutions within a structured framework of action from a regulatory and clinical trial perspective. New developments within the field of immunophenotyping using multiplexed tissue imaging platforms and associated digital pathology are also described, with a specific focus on translational implications across different subtypes of cancer. © 2024 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Treatment Response, Tumor Infiltrating Lymphocytes and Clinical Outcomes in Inflammatory Breast Cancer-Treated with Neoadjuvant Systemic Therapy

Inflammatory breast cancer (IBC) is a rare (1%-5%), aggressive form of breast cancer, accounting for approximately 10% of breast cancer mortality. In the localized setting, standard of care is neoadjuvant chemotherapy (NACT) ± anti-HER2 therapy, followed by surgery. Here we investigated associations between clinicopathologic variables, stromal tumor-infiltrating lymphocytes (sTIL), and pathologic complete response (pCR), and the prognostic value of pCR. We included 494 localized patients with IBC treated with NACT from October 1996 to October 2021 in eight European hospitals. Standard clinicopathologic variables were collected and central pathologic review was performed, including sTIL. Associations were assessed using Firth logistic regression models. Cox regressions were used to evaluate the role of pCR and residual cancer burden (RCB) on disease-free survival (DFS), distant recurrence-free survival (DRFS), and overall survival (OS). Distribution according to receptor status was as follows: 26.4% estrogen receptor negative (ER-)/HER2-; 22.0% ER-/HER2+; 37.4% ER+/HER2-, and 14.1% ER+/HER2+. Overall pCR rate was 26.3%, being highest in the HER2+ groups (45.9% for ER-/HER2+ and 42.9% for ER+/HER2+). sTILs were low (median: 5.3%), being highest in the ER-/HER2- group (median: 10%). High tumor grade, ER negativity, HER2 positivity, higher sTILs, and taxane-based NACT were significantly associated with pCR. pCR was associated with improved DFS, DRFS, and OS in multivariable analyses. RCB score in patients not achieving pCR was independently associated with survival. In conclusion, sTILs were low in IBC, but were predictive of pCR. Both pCR and RCB have an independent prognostic role in IBC treated with NACT.

SIGNIFICANCE

IBC is a rare, but very aggressive type of breast cancer. The prognostic role of pCR after systemic therapy and the predictive value of sTILs for pCR are well established in the general breast cancer population; however, only limited information is available in IBC. We assembled the largest retrospective IBC series so far and demonstrated that sTIL is predictive of pCR. We emphasize that reaching pCR remains of utmost importance in IBC.

Histopathological growth patterns and tumor-infiltrating lymphocytes in breast cancer liver metastases

Liver is the third most common organ for breast cancer (BC) metastasis. Two main histopathological growth patterns (HGP) exist in liver metastases (LM): desmoplastic and replacement. Although a reduced immunotherapy efficacy is reported in patients with LM, tumor-infiltrating lymphocytes (TIL) have not yet been investigated in BCLM. Here, we evaluate the distribution of the HGP and TIL in BCLM, and their association with clinicopathological variables and survival. We collect samples from surgically resected BCLM (n = 133 patients, 568 H&E sections) and post-mortem derived BCLM (n = 23 patients, 97 H&E sections). HGP is assessed as the proportion of tumor liver interface and categorized as pure-replacement ('pure r-HGP') or any-desmoplastic ('any d-HGP'). We score the TIL according to LM-specific guidelines. Associations with progression-free (PFS) and overall survival (OS) are assessed using Cox regressions. We observe a higher prevalence of 'any d-HGP' (56%) in the surgical samples and a higher prevalence of 'pure r-HGP' (83%) in the post-mortem samples. In the surgical cohort, no evidence of the association between HGP and clinicopathological characteristics is observed except with the laterality of the primary tumor (p value = 0.049) and the systemic preoperative treatment before liver surgery (p value = .039). TIL is less prevalent in 'pure r-HGP' as compared to 'any d-HGP' (p value = 0.001). 'Pure r-HGP' predicts worse PFS (HR: 2.65; CI: (1.45-4.82); p value = 0.001) and OS (HR: 3.10; CI: (1.29-7.46); p value = 0.011) in the multivariable analyses. To conclude, we demonstrate that BCLM with a 'pure r-HGP' is associated with less TIL and with the worse outcome when compared with BCLM with 'any d-HGP'. These findings suggest that HGP could be considered to refine treatment approaches.

First-in-human study of SBRT and adenosine pathway blockade to potentiate the benefit of immunochemotherapy in early-stage luminal B breast cancer: results of the safety run-in phase of the Neo-CheckRay trial

BACKGROUND

Luminal B breast cancer (BC) presents a worse prognosis when compared with luminal A BC and exhibits a lower sensitivity to chemotherapy and a lower immunogenicity in contrast to non-luminal BC subtypes. The Neo-CheckRay clinical trial investigates the use of stereotactic body radiation therapy (SBRT) directed to the primary tumor in combination with the adenosine pathway inhibitor oleclumab to improve the response to neo-adjuvant immuno-chemotherapy in luminal B BC. The trial consists of a safety run-in followed by a randomized phase II trial. Here, we present the results of the first-in-human safety run-in.

METHODS

The safety run-in was an open-label, single-arm trial in which six patients with early-stage luminal B BC received the following neo-adjuvant regimen: paclitaxel q1w×12 → doxorubicin/cyclophosphamide q2w×4; durvalumab (anti-programmed cell death receptor ligand 1 (PD-L1)) q4w×5; oleclumab (anti-CD73) q2w×4 → q4w×3 and 3×8 Gy SBRT to the primary tumor at week 5. Surgery must be performed 2-6 weeks after primary systemic treatment and adjuvant therapy was given per local guidelines, RT boost to the tumor bed was not allowed. Key inclusion criteria were: luminal BC, Ki67≥15% or histological grade 3, MammaPrint high risk, tumor size≥1.5 cm. Primary tumor tissue samples were collected at three timepoints: baseline, 1 week after SBRT and at surgery. Tumor-infiltrating lymphocytes, PD-L1 and CD73 were evaluated at each timepoint, and residual cancer burden (RCB) was calculated at surgery.

RESULTS

Six patients were included between November 2019 and March 2020. Median age was 53 years, range 37-69. All patients received SBRT and underwent surgery 2-4 weeks after the last treatment. After a median follow-up time of 2 years after surgery, one grade 3 adverse event (AE) was reported: pericarditis with rapid resolution under corticosteroids. No grade 4-5 AE were documented. Overall cosmetical breast evaluation after surgery was 'excellent' in four patients and 'good' in two patients. RCB results were 2/6 RCB 0; 2/6 RCB 1; 1/6 RCB 2 and 1/6 RCB 3.

CONCLUSIONS

This novel treatment combination was considered safe and is worth further investigation in a randomized phase II trial.

TRIAL REGISTRATION NUMBER

NCT03875573.

Initial interactions with the FDA on developing a validation dataset as a medical device development tool

Quantifying tumor-infiltrating lymphocytes (TILs) in breast cancer tumors is a challenging task for pathologists. With the advent of whole slide imaging that digitizes glass slides, it is possible to apply computational models to quantify TILs for pathologists. Development of computational models requires significant time, expertise, consensus, and investment. To reduce this burden, we are preparing a dataset for developers to validate their models and a proposal to the Medical Device Development Tool (MDDT) program in the Center for Devices and Radiological Health of the U.S. Food and Drug Administration (FDA). If the FDA qualifies the dataset for its submitted context of use, model developers can use it in a regulatory submission within the qualified context of use without additional documentation. Our dataset aims at reducing the regulatory burden placed on developers of models that estimate the density of TILs and will allow head-to-head comparison of multiple computational models on the same data. In this paper, we discuss the MDDT preparation and submission process, including the feedback we received from our initial interactions with the FDA and propose how a qualified MDDT validation dataset could be a mechanism for open, fair, and consistent measures of computational model performance. Our experiences will help the community understand what the FDA considers relevant and appropriate (from the perspective of the submitter), at the early stages of the MDDT submission process, for validating stromal TIL density estimation models and other potential computational models. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Paclitaxel plus carboplatin and durvalumab with or without oleclumab for women with previously untreated locally advanced or metastatic triple-negative breast cancer: the randomized SYNERGY phase I/II trial

Chemo-immunotherapy is the first-line standard of care for patients with PD-L1 positive metastatic triple-negative breast cancer (mTNBC). SYNERGY (NCT03616886) is a dose-finding phase I and a randomized phase II, open-label trial evaluating if targeting the immunosuppressive adenosine pathway can enhance the antitumor activity of chemo-immunotherapy. The phase I part included 6 patients with untreated locally-advanced or mTNBC to determine the safety and recommended phase II dose of the anti-CD73 antibody oleclumab in combination with the anti-PD-L1 durvalumab and 12 cycles of weekly carboplatin and paclitaxel. In the phase II part, 127 women were randomized 1:1 to receive chemo-immunotherapy, with (arm A) or without (arm B) oleclumab. The primary endpoint was the clinical benefit rate at week 24, defined as stable disease, partial or complete response per RECIST v1.1. Secondary endpoints included objective response rate, duration of response, survival outcomes (progression-free survival and overall survival), and safety. The trial did not meet its primary endpoint, as the 24-week clinical benefit rate was not significantly improved by adding oleclumab (43% vs. 44%, p = 0.61). Exploratory median progression-free survival was 5.9 months in arm A as compared to 7.0 months in arm B (p = 0.90). The safety profile was manageable in both arms.

Histopathological growth pattern of liver metastases as an independent marker of metastatic behavior in different primary cancers

Surgical resection can lead to prolonged survival in patients with isolated liver metastases (LM) from various primary cancers. However, there are currently no validated predictive markers to discriminate between these oligo/argometastatic patients, who will benefit from surgery, and those with diffuse metastatic behavior in whom surgery will be futile. To evaluate whether the tumor microenvironment, or histopathological growth pattern (HGP), of LM reflects the type of metastatic progression independently of the origin of the primary cancer, we analyzed a combined series of patients who underwent surgery for colorectal LM (N=263) or non-colorectal LM (N=66). HGPs of LM were scored in each patient to distinguish between desmoplastic HGP (all LM showing a complete encapsulated pattern) and non-desmoplastic HGP (at least one LM with some infiltrating-replacement component). In the entire series, 5-year overall and progression-free survival were, 44.5% and 15.5%, respectively, with no significant differences between colorectal and non-colorectal LM. In patients with desmoplastic HGP, 5-year overall and progression-free survival were 57% and 32%, respectively, as compared to 41% and 12%, respectively, in patients with non-desmoplastic-HGP (p=0.03 and 0.005). Irrespective of cancer origin and compared to traditional risk factors, desmoplastic HGP was the most significant predictor for better post-operative overall survival (adjusted HR: 0.62; 95% CI: [0.49-0.97]; p=0.035) and progression-free survival (adjusted HR: 0.61; 95% CI: [0.42-0.87], p=0.006). This suggests that the HGP of LM may represent an accurate marker that reflects the mode of metastatic behavior, independently of primary cancer type.

Association between primary tumor characteristics and histopathological growth pattern of liver metastases in colorectal cancer

INTRODUCTION

The microarchitecture of liver metastases (LMs), or histopathological growth pattern (HGP), has been demonstrated to be a significant prognostic factor in patients undergoing resection of colorectal liver metastases (CRLMs). Currently, however, HGP can be only determined on the operative specimen. Therefore, the development of new tools to predict the HGP of CRLMs before surgery and to understand the mechanisms that drive these patterns is important for improving individualization of therapeutic management. In this study, we analyzed data from a retrospective series of patients who underwent surgery for CRLMs to compare primary tumor characteristics, including markers of local aggressiveness and migratory capacity, and HGP of liver metastases.

METHODS

Data from a retrospective series of 167 patients who underwent curative-intent resection of CRLMs and in whom pathological samples from both primary tumor and liver metastases were available were reviewed. At the primary tumor level, KRAS mutational status, grade of differentiation, and tumor budding were assessed. HGP was scored in each resected CRLM, according to consensus guidelines, and classified as desmoplastic (dHGP) or non-desmoplastic (non-dHGP). Associations between primary tumor characteristics and HGP of CRLMs were evaluated using a binary logistic regression model. Overall survival and disease-free survival were evaluated using Kaplan-Meier and multivariable Cox regression analyses.

RESULTS

CRLMs were classified as dHGP in 36% of the patients and as non-dHGP in 64%. Higher rates of moderately or poorly differentiated primary tumors were observed in the non-dHGP CRLM group (80%), as compared with the dHGP group (60%) (OR = 3.6; 95%CI: 1.6-7.05; p = 0.001). Higher rates of tumor budding were observed in the non-dHGP CRLM group, with a median tumor budding value of 4 as compared with 2.5 in the dHGP group (p = 0.042). In the entire series, 5-year overall and disease-free survival were 43% and 32.5%, respectively. The non-dHGP CRLM group had worse post-hepatectomy survival, with 5-year overall and disease-free survival of 32.2% and 24.6%, respectively, as compared with 60.8% and 45.9%, respectively, for the dHGP group (p = 0.02).

CONCLUSION

Colorectal tumors with moderate or poor differentiation and those with high tumor budding are more frequently associated with CRLMs with a non-dHGP. This suggests that primary tumor characteristics of local aggressiveness and migratory capacity could preferentially promote the development of CRLMs with an infiltrating pattern and that these parameters should be considered as part of new scores for predicting HGP before surgery. This finding may stimulate new lines of research for more individualized therapeutic decision in patients with CRLM candidate to surgery.

Axillary Surgical Attitude Changing with Retrospective Application of ACOSOG Z0011 Eligible Criteria: An Institutional Evaluation

Objective

Sentinel lymph node biopsy (SLNB) represents the gold standard for axillary surgical staging. The aim of this study was to assess the proportion of axillary lymph node dissection (ALND) that could be avoided after retrospective application of the ACOSOG Z0011 criteria and to evaluate the shortterm complications associated with axillary surgery.

Materials and Methods

We reviewed breast cancer (BC) patients treated by primary breast-conserving surgery from 2012 to 2015. The percentage of SLNB vs ALND performed before and after the application of the ACOSOG Z0011 criteria was calculated. Complications were analyzed using crosstabs, with p<0.05 considered significant.

Results

Two hundred fifty one patients with a median age of 59.3 years were included. BC tumors had a median size of 13 mm and were mostly unifocal (83.9%). There were 30.3% with 1-2 metastatic lymph nodes (MLN). ALND was performed in 44.2%. The patients with 1-2 MLN, had only SLNB in 14.5% of cases. By applying the ACOSOG Z0011 criteria, ALND would have been avoided in 40.2% of patients. At least one postoperative complication was reported after SLNB or ALND for 45.7% and 74.7% of patients respectively. Seroma was the most frequent complication, and occurred in 29.3% of cases after SLNB and in 59.5% after ALND.

Conclusion

SNLB is the most commonly used axillary surgical staging procedure in this series (55.8%). With a retrospective application of the ACOSOG Z0011 criteria in our population, ALND could have been avoided for 40.2% patients. Post-operative complications rate was higher after ALND, with a seroma rate at 59.5%.

Association of body mass index with clinicopathological features and survival in patients with primary invasive lobular breast cancer

PURPOSE

Invasive lobular carcinoma (ILC) represents up to 15% of all breast carcinomas. While the proportion of women with overweight and obesity increases globally, the impact of body mass index (BMI) at primary diagnosis on clinicopathological features of ILC and the prognosis of the patients has not been investigated yet.

PATIENTS AND METHODS

We performed a multicentric retrospective study including patients diagnosed with non-metastatic pure ILC. The association of BMI at diagnosis with clinicopathological variables was assessed using linear or multinomial logistic regression. Univariable and multivariable survival analyses were performed to evaluate the association of BMI with disease-free survival (DFS), distant recurrence-free survival (DRFS), and overall survival (OS).

RESULTS

The data of 2856 patients with ILC and available BMI at diagnosis were collected, of which 2570/2856 (90.0%) had oestrogen receptor (ER)-positive and human epidermal growth factor receptor (HER2) not amplified/overexpressed (ER+/HER2-) ILC. Of these 2570 patients, 80 were underweight (3.1%), 1410 were lean (54.9%), 712 were overweight (27.7%), and 368 were obese (14.3%). Older age at diagnosis, a higher tumour grade, a larger tumour size, a nodal involvement, and multifocality were associated with a higher BMI. In univariable models, higher BMI was associated with worse outcomes for all end-points (DFS: hazard ratio (HR) 1.21, 95CI 1.12-1.31, p value<0.01; DRFS: HR 1.25, 95CI 1.12-1.40, p value<0.01; OS: HR 1.25, 95CI 1.13-1.37, p value<0.01). This association was not statistically significant in multivariable analyses (DFS: HR 1.09, 95CI 0.99-1.20, p value 0.08; DRFS: HR 1.03, 95CI 0.89-1.20, p value 0.67; OS: HR 1.11, 95CI 0.99-1.24, p value 0.08), whereas grade, tumour size, and nodal involvement were still prognostic for all end-points.

CONCLUSION

Worse prognostic factors such as higher grade, larger tumour size, and nodal involvement are associated with higher BMI in ER+/HER2- ILC, while there was no statistical evidence for an independent prognostic role for BMI. Therefore, we hypothesise that the effect of BMI on survival could be mediated through its association with these clinicopathological variables.

Pitfalls in machine learning-based assessment of tumor-infiltrating lymphocytes in breast cancer: A report of the International Immuno-Oncology Biomarker Working Group on Breast Cancer

The clinical significance of the tumor-immune interaction in breast cancer is now established, and tumor-infiltrating lymphocytes (TILs) have emerged as predictive and prognostic biomarkers for patients with triple-negative (estrogen receptor, progesterone receptor, and HER2-negative) breast cancer and HER2-positive breast cancer. How computational assessments of TILs might complement manual TIL assessment in trial and daily practices is currently debated. Recent efforts to use machine learning (ML) to automatically evaluate TILs have shown promising results. We review state-of-the-art approaches and identify pitfalls and challenges of automated TIL evaluation by studying the root cause of ML discordances in comparison to manual TIL quantification. We categorize our findings into four main topics: (1) technical slide issues, (2) ML and image analysis aspects, (3) data challenges, and (4) validation issues. The main reason for discordant assessments is the inclusion of false-positive areas or cells identified by performance on certain tissue patterns or design choices in the computational implementation. To aid the adoption of ML for TIL assessment, we provide an in-depth discussion of ML and image analysis, including validation issues that need to be considered before reliable computational reporting of TILs can be incorporated into the trial and routine clinical management of patients with triple-negative breast cancer. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Spatial analyses of immune cell infiltration in cancer: current methods and future directions: A report of the International Immuno-Oncology Biomarker Working Group on Breast Cancer

Modern histologic imaging platforms coupled with machine learning methods have provided new opportunities to map the spatial distribution of immune cells in the tumor microenvironment. However, there exists no standardized method for describing or analyzing spatial immune cell data, and most reported spatial analyses are rudimentary. In this review, we provide an overview of two approaches for reporting and analyzing spatial data (raster versus vector-based). We then provide a compendium of spatial immune cell metrics that have been reported in the literature, summarizing prognostic associations in the context of a variety of cancers. We conclude by discussing two well-described clinical biomarkers, the breast cancer stromal tumor infiltrating lymphocytes score and the colon cancer Immunoscore, and describe investigative opportunities to improve clinical utility of these spatial biomarkers. © 2023 The Pathological Society of Great Britain and Ireland.

Effectiveness of Carbon Localization for Invasive Breast Cancer: An Institutional Experience

Introduction

The final oncological and aesthetic results of breast-conserving surgery (BCS) are influenced by the precise localization of breast cancer (BC) tumors and by the quality of the intraoperative margin assessment technique. This study aimed to assess the effectiveness of the carbon localization (CL) technique by determining the success rate of BC identification and the proportion of adequate complete resection of BC lesions.

Methods

We conducted a cross-sectional retrospective study of patients treated with primary BCS for invasive BC who underwent CL of their BC lesion at the Jules Bordet Institute between January 2015 and December 2017. Descriptive statistics with categorical and continuous variables were used. The success rate of tumor identification and the rate of adequate excision were calculated using the test of percentages for independent dichotomous data.

Results

This study included 542 patients with 564 nonpalpable BC lesions. The median pathological tumor size was 12 mm. Of these, 460 were invasive ductal carcinomas. Most of the tumors were of the luminal subtype. CL was performed using ultrasound guidance in 98.5% of cases. The median delay between CL and surgery was 5 days, with 46% of the patients having CL one day before surgery. The lumpectomy weighed 38 g on average, with a median diameter of the surgical sample at 6 cm and a median volume of 44 cm³ (6-369). One-stage complete resection was successfully performed in 93.4% of cases. In 36% of cases, an intraoperative re-excision was performed, based on intraoperative macroscopic pathological margin evaluation. The tumor was identified in 98.9% of cases in the breast surgical specimen.

Conclusion

This study demonstrated high success rates for BC tumor identification (99%) and one-stage complete resection (93.4%) after BCS and CL. These results show that CL is an effective, simple, and inexpensive localization technique for successful excision of BC lesions during BCS.

PIK3CA copy number gain and inhibitors of the PI3K/AKT/mTOR pathway in triple-negative breast cancer

As wider insights are gained on the molecular landscape of triple-negative breast cancer (TNBC), novel targeted therapeutic strategies might become an option in this setting as well. Activating mutations of PIK3CA represent the second most common alteration in TNBC after the TP53 mutation, with a prevalence of about 10-15%. Considering the well-established predictive role of PIK3CA mutations for response to agents targeting the PI3K/AKT/mTOR pathway, several clinical trials are currently evaluating these drugs in patients with advanced TNBC. However, much less is known regarding the actionability of PIK3CA copy number gains, which represent a thoroughly common molecular alteration in TNBC, with a prevalence estimated at 6-20%, and are listed as "likely gain-of-function" alterations in the OncoKB database. In the present paper we describe two clinical cases in which patients harboring PIK3CA-amplified TNBC received a targeted treatment with the mTOR-inhibitor everolimus and the PI3K-inhibitor alpelisib, respectively, with evidence of disease response on 18F-FDG Positron-emission tomography (PET) imaging. Hence, we discuss the evidence presently available regarding a possible predictive value of PIK3CA amplification for response to targeted treatment strategies, suggesting that this molecular alteration might represent an intriguing biomarker in this sense. Considering that few of the currently active clinical trials assessing agents targeting the PI3K/AKT/mTOR pathway in TNBC select patients based on tumor molecular characterization, and none of these based on PIK3CA copy number status, we urge for the introduction of PIK3CA amplification as a criterion for patient selection in future clinical trials in this setting.

Abstract P6-01-47: Stromal tumor infiltrating lymphocytes and pathological complete response in patients with inflammatory breast cancer treated with neoadjuvant chemotherapy

Background: Inflammatory breast cancer (IBC) is a rare (1-5%), but aggressive form of breast cancer (BC), accounting for ~10% of BC mortality. In early setting (M0), standard of care is neoadjuvant chemotherapy (NACT), followed by surgery. Nevertheless, outcome is still relatively poor. Pathological complete response (pCR) after NACT is prognostic in BC in general, and can be predicted by a high percentage of stromal tumor infiltrating lymphocytes (sTIL) in the primary tumor. The predictive value of sTIL in IBC has only been sporadically investigated, often in smaller series. Our aim was to determine which variables, including sTIL, are associated with pCR and to determine the prognostic value of pCR in IBC in a large multicentric, retrospective cohort. Patients & Methods: We included patients with IBC treated with NACT+/- anti-Human Epidermal growth factor Receptor 2 (HER2) therapy, followed by surgery from 10/1996 to 10/2021 in 7 different European hospitals. Clinicopathological variables were collected and central pathological review was performed, including sTIL scoring. This study focused on M0 cases. Considered clinicopathological variables were: age, histology, tumor grade, estrogen receptor status (ER), HER2 status, focality (unifocal vs not), and baseline locoregional nodal status (Table 1). Associations between pCR, clinicopathological variables and sTIL were assessed using Firth’s logistic regression models: Model 1 was adjusted for center, Model 2 additionally included all variables of interest. Similarly, linear regression was used to investigate the association between sTIL and clinicopathological features. Univariable and multivariable Cox regression was used to evaluate the role of pCR on disease free survival (DFS), distant recurrence free survival (DRFS) and overall survival (OS). DFS and DRFS were analyzed considering death without the respective event as competing risk. Results: 494 patients were included. The distribution according to receptor status was: ER-/HER2- (24.3%), ER+/HER2- (34.4%), ER+/HER2+ (13%) and ER-/HER2+ (20.2%). pCR rate was 26% and per receptor status: ER-/HER2- (28%), ER+/HER2- (10%), ER+/HER2+ (42%) and ER-/HER2+ (45%). pCR was associated with grade (G3 vs G1/2, OR =2.79 (1.70 − 4.74), p &lt; .001), ER-status (positive vs negative, OR = 0.39 (0.26 − 0.60), p &lt; .001) and HER2 status (positive vs negative, OR = 3.74 (2.43 − 5.81), p &lt; .001) in Model 1. Only the association with HER2 status remained significant in Model 2 (OR = 5.34 (2.83 − 10.47), p &lt; .001). sTIL was scored for 385 patients. Median sTIL was 5.3% [IQR 2.0%;16.7%] and according to receptor status: ER-/HER2- (10%), ER+/HER2- (2.5%), ER+/HER2+ (6.7%) and ER-/HER2+ (8.3%). Higher sTIL was associated with NST (p = .032), grade 3 (p = .015), and ER-negativity (p = .007) in Model 1. This was no longer significant in Model 2, but the direction of the trends was preserved. sTIL was associated with pCR (5% increment, OR = 1.13 (1.05 − 1.22), p = .002), but no longer after adjustment. No association between pCR and sTIL was found stratifying by receptor status. The median FU was 9.4 years and multivariable Cox regression models revealed that ER+ and HER2+ status and achieving pCR were significantly associated with better DFS, DRFS, and OS (Table 1). Conclusion: Our results indicate that patients with HER2+ tumors have a higher probability of achieving pCR and that pCR has an independent prognostic role in IBC. This is the largest IBC study with centrally scored sTIL, demonstrating that sTIL is associated with pCR but its role as an independent predictor of pCR is still not certain.

Citation Format: Maxim De Schepper, Ha-Linh Nguyen, François Richard, Florence Lerebours, Roman Vion, Florian Clatot, Anca Berghian, Marion Maetens, Sophia Leduc, Edoardo Isnaldi, Chiara Molinelli, Matteo Lambertini, Frederica Grillo, Gabriele Zoppoli, Luc Dirix, Hilde Wuyts, Kevin Punie, Hans Wildiers, Chantal Remmerie, Ann Smeets, Ines Nevelsteen, Patrick Neven, Anne Salomon, Denis Larsimont, Caroline Duhem, Patrice Viens, François BERTUCCI, Elia Biganzoli, Peter Vermeulen, Giuseppe Floris, Christine Desmedt. Stromal tumor infiltrating lymphocytes and pathological complete response in patients with inflammatory breast cancer treated with neoadjuvant chemotherapy [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P6-01-47.

Abstract PD4-01: PD4-01 Spatial transcriptomics reveals a substantial heterogeneity in TNBC tumor and stroma compartments with potential clinical implications

Background Triple negative breast cancer (TNBC) is a heterogeneous disease characterized by at least five molecular subtypes, namely basal like (BL), immunomodulatory (IM), luminal androgen receptor (LAR), mesenchymal (M) and mesenchymal stem like (MSL), associated with distinct gene expression, genomic and tumor microenvironment (TME) profiles. Recent technological advances allow to investigate intratumor geographic heterogeneity ignored by bulk tumor analyses. Here, we deployed spatial transcriptomics (ST) to interrogate tumor and stroma compartments heterogeneity and assess its association with clinical outcome. Methods Spatial transcriptomics (Visium® Spatial Gene Expression, 10X Genomics) was performed on a retrospective series of 94 case-control TNBC samples matched for known clinic-pathological parameters with available long term outcome. Detailed morphological annotations spanning 11 histomorphological categories were performed by a breast dedicated pathologist assisted by the automated QuPath digital pathology software. Bioinformatic analyses were performed using in house pipelines. Results We investigated the distribution of each morphological category across the five TNBC molecular subtypes. We found that LAR, M and MSL, even though they had less tumor cells, had more patches of very small size (p&lt; 0.0001). On the other hand, BL and IM had few large and dense patches. Stroma had an opposite distribution compared to tumor, with LAR and MSL being enriched with stroma (p&lt; 00001). Tumor infiltrating lymphocytes were specific of the IM (p&lt; 0.0001) and to a lesser extent the BL subtype. Normal structures, like fat tissue (p&lt; 0.008), lactiferous ducts (p&lt; 0.03) and vessels (p&lt; 0.02), were more present in MSL and LAR. The differences between the molecular subtypes are mirrored at the level of their cell composition and tumor organization, suggesting the possibility to assess TNBC molecular subtypes from imaging data alone. At the gene expression level, spatial deconvolution analyses revealed the co-existence of tumor and stroma compartments from different TNBC subtypes within a tumor sample of a given subtype as defined by bulk tumor analysis. Interestingly, these different tumor-stroma combinations were associated with prognosis. For example, M tumors associated with MSL stroma seem to have a better prognosis than M tumors with an M stroma (p=0.001). Furthermore, spatial resolution of the gene expression identified 418 individual clusters (median 4 clusters per sample) associated with specific molecular and cellular features highlighting a substantial intra-patient heterogeneity. These clusters were further grouped into 11 ecotypes associated with distinct hallmarks and pathways, including EMT, angiogenesis, DNA repair and immune profiles revealing an important inter-patient heterogeneity beyond TNBC classification. Interestingly, 2 ecotypes were identified within the IM subtype associated with distinct clinical outcome, with ecotype 6 characterized by high EMT, mesenchymal stroma and worse prognosis (p = 0,021). Conclusion To our knowledge, this is the largest study demonstrating the substantial intra- and inter-patient heterogeneity characterizing TNBC at an unprecedented level, with differences both in tumor and stroma composition as well as spatial organization and clinical outcome. Our results hightlight the need to consider TNBC heterogeneity for patient care and future clinical development including immunotherapy.

Citation Format: Xiaoxiao Wang, David Venet, Frédéric Lifrange, Denis Larsimont, Mattia Rediti, Linnea Stenbeck, David Gacquer, Floriane Dupont, Ghizlane Rouas, Matteo Serra, Joakim Lundeberg, Françoise Rothé, Christos Sotiriou. PD4-01 Spatial transcriptomics reveals a substantial heterogeneity in TNBC tumor and stroma compartments with potential clinical implications [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD4-01.

Abstract P3-05-40: Association of body mass index with clinicopathological features and survival in patients with primary ER+/HER2- invasive lobular breast cancer

Background: Invasive lobular carcinoma (ILC) represents up to 15% of all breast carcinomas. The majority of ILC express the estrogen receptor (ER) and have no amplification/overexpression of the human epidermal growth factor receptor 2 (HER2). A high body mass index (BMI) has been associated with an increased risk of developing ILC in postmenopausal women, similar to what is seen for breast cancer of no special type (NST). It is however unknown if BMI impacts the clinicopathological features and the prognosis of ILC.

Methods: We performed a multicentric retrospective study in 5 European centers of patients diagnosed between January 2000 and December 2020 with ER+/HER2- non-metastatic pure (i.e., not mixed) ILC. Patient and tumor characteristics and event-related data were collected. BMI was categorized into underweight (≤18.5kg/m2), lean (&gt;18.5kg/m2 and &lt; 25kg/m2), overweight (≥25kg/m2 and &lt; 30kg/m2) and obese (≥30kg/m2). The association of BMI as either a continuous or a categorical variable with clinicopathological variables was assessed using linear regression or ordinal logistic regression, respectively. Median follow-up was calculated using the reverse Kaplan-Meier estimator. Survival analyses using univariable (stratified by center) and multivariable (adjusted for all included variables and stratified by center) Cox regression were performed to evaluate the association of BMI with disease free survival (DFS), distant recurrence free survival (DRFS) and overall survival (OS). DFS and DRFS were analyzed in the presence of death without event as the competing risk.

Results: The data of 2476 patients were collected and BMI was available for 2346 patients. In total, 1299 (55%) patients were lean, 638 (27%) overweight and 339 (14%) obese. Underweight patients only represented 3% of all patients and were thus excluded from further analyses. A higher age at diagnosis, higher grade, larger tumor size, nodal involvement and multifocality were significantly associated with higher BMI (Table 1). The median follow-up was 8,5 years (interquartile range 59.24 – 142.13 months). In univariable analysis, higher BMI was associated with worse survival outcomes (Table 2). However, this association was not seen in multivariable analysis while grade, tumor size and nodal involvement were still prognostic for all endpoints. Similar results were seen with BMI as a continuous variable.

Conclusion: Larger tumors and nodal involvement were more likely to be found in patients with ER+/HER2- ILC with higher BMI which might be explained by a delayed diagnosis in these patients. Higher grade also seemed to be associated with higher BMI. In multivariable analyses, BMI was not found to be an independent prognostic factor. Tumor grade, tumor size, and nodal status remained strongly prognostic for survival outcomes in multivariable survival analyses which is consistent with their known prognostic importance in luminal tumors. We hypothesize that the prognostic effect of BMI is mediated through these variables for patients with ER+/HER2- ILC.

Table 1. Association of clinicopathological features of ER+/HER2- ILC with categorical BMI.

Table 2. Association of categorical BMI and other clinicopathological features of ER+/HER2- ILC with survival.

Citation Format: Karen Van Baelen, Ha-Linh Nguyen, François Richard, Anne-Sophie Hamy, Aullène Toussaint, Fabien Reyal, Anne Salomon, Luc Dirix, Peter Vermeulen, Hilde Wuyts, Maria Karsten, Adam D. Dordevic, Guilherme Nader Marta, Evandro de Azambuja, Christos Sotiriou, Denis Larsimont, Ottavia Amato, Marion Maetens, Maxim De Schepper, Tatjana Geukens, Sileny Han, Thaïs Baert, Kevin Punie, Hans Wildiers, Chantal Remmerie, Ann Smeets, Ines Nevelsteen, Giuseppe Floris, Elia Biganzoli, Patrick Neven, Christine Desmedt. Association of body mass index with clinicopathological features and survival in patients with primary ER+/HER2- invasive lobular breast cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-05-40.

Abstract P2-21-01: Decoding Inter- and Intra-Tumor Heterogeneity in Lobular Breast Cancer Using Spatial Transcriptomics and Clustering Analysis

Background: Invasive lobular breast carcinoma (ILC) represents 5 to 15% of all invasive breast cancers. Recent studies showed the importance of tumor microenvironment (TME) heterogeneity on patient outcome. Here, we aim to characterize TME spatial heterogeneity by performing clustering analysis on spatial transcriptomics (ST) data. Methods: Frozen tumor samples from 43 primary estrogen receptor positive, HER2-negative ILCs were characterized using ST (Visium, 10x Genomics), each ST slide containing 4992 spots. Hematoxylin/eosin (H&E) stained ST slides were annotated (QuPath software) reaching single cell resolution. After performing normalization, hierarchical clustering (STutility R package) across all samples was carried out on principal components computed using highly variable genes. Clusters were characterized using morphological annotation and gene set enrichment analysis for hallmark gene sets from MSigDB (FGSEA R package). A cluster of spots was defined as tumoral or stromal if the average proportion of pixels annotated as tumor or stroma across its constitutive spots was higher than the average proportion of tumor or stroma pixels across all spots of our cohort. Spatial heterogeneity was assessed by comparing the number of contacts between spots belonging to the same cluster (homo-contacts) and the number of contacts between spots belonging to different clusters (hetero-contacts). Comparisons between groups were assessed using Wilcoxon test. Results: Out of the 43 ILC samples, 19 were T2 or T3, 13 were node-positive and 34 were grade 2. Of note, 9 patients experienced disease relapse. Morphological annotation revealed that an average of 20.4%, 61.12%, 11.5%, 0.45%, 3% of the tissues in our dataset corresponded to tumor, stroma, adipose tissue, immune infiltrate and normal structures (vessels, normal breast), respectively. Bioinformatics analysis revealed 7 tumor, 11 stroma, and 6 normal structures clusters, as well as 8 mixed clusters with no predominant morphological structure, with a median of 22 clusters per sample. Tumor and stroma clusters were either shared across all samples or present only in specific samples. Overall, tumor clusters were characterized by an enrichment in estrogen and androgen response related pathways. Moreover, tumor clusters enriched in oxidative phosphorylation, G2M checkpoint and MYC targets were more present in samples with higher histopathological grade (p=0.016), whereas tumor clusters enriched in interferon alpha/gamma response related pathway were associated with a higher tumor stage (p=0.007). A higher number of hetero-contacts among tumor spots were associated with disease relapse (p=0.02). Similarly, a higher number of hetero-contacts among stroma spots including immune and adipose related clusters was also found in samples from patients who experienced disease relapse (p=0.01). Overall, these findings suggest a role of both tumor and stroma spatial disorganization and heterogeneity in tumor progression. Furthermore, clusters capturing the presence of normal breast and in situ carcinoma were enriched in samples from patients who did not relapse (p&lt; 0.001). Conclusion: Our results revealed the substantial inter- and intra-patient heterogeneity of ILC both at the tumor and microenvironment levels. Different tumor and stroma clusters characterized by specific hallmarks were associated to specific clinical features and disease outcome, unraveling potential new targets for optimizing ILC care. Further validation is needed.

Citation Format: Matteo Serra, Mattia Rediti, Frédéric Lifrange, David Venet, Nicola Occelli, Laetitia Collet, Delphine Vincent, Ghizlane Rouas, Ligia Craciun, Denis Larsimont, Miikka Vikkula, Francois P. Duhoux, Françoise Rothé, Christos Sotiriou. Decoding Inter- and Intra-Tumor Heterogeneity in Lobular Breast Cancer Using Spatial Transcriptomics and Clustering Analysis [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-21-01.

HER2 Amplification in p53-Mutated Endometrial Carcinomas

p53-mutated endometrial carcinomas tend to recur and develop distant metastases. Therefore, the detection of new potential therapeutic targets such as HER2 is particularly interesting. In this retrospective study, which considered over 118 endometrial carcinomas, the p53 mutation was detected in 29.6% of cases. In these cases, the HER2 protein profile was studied via immunohistochemistry, and an overexpression of HER2 protein (++ or +++) was noted in 31.4%. The CISH technique was used in these cases to determine if gene amplification was present. In 18% of cases, the technique was not conclusive. Amplification of the HER2 gene was observed in 36.3% of cases and 36.3% of cases showed a polysomal-like aneusomy for centromere 17. Amplification was found in serous carcinomas, clear cell carcinomas and carcinosarcomas, highlighting the future potentiality of HER2-targeted therapies in these variants of aggressive carcinomas.

Tumor biology reflected by histological growth pattern is more important than surgical margin for the prognosis of patients undergoing resection of colorectal liver metastases

INTRODUCTION

The histological growth pattern (HGP) of colorectal liver metastases (CRLMs) reflects tumor biology and local infiltrating behavior. In patients undergoing surgery for CRLMs, we investigated whether HGP and surgical margin status interact when influencing prognosis.

METHODS

Clinicopathological data, margin status, and HGP were reviewed in patients who underwent resection of CRLMs. R1 margin was defined when cancer cells were present at any point along the margin. HGPs were scored according to international guidelines, identifying patients with desmoplastic (DHGP) or non-desmoplastic (non-DHGP) CRLMs.

RESULTS

Among 299 patients, 16% had R1 resection and 81% had non-DHGP CRLMs. Non-DHGP was the only predictive factor for R1 resection (18.7% versus 7.4% in DHGP, p = 0.04). Poorer 5-year overall survival was observed in both R1 and non-DHGP groups in univariate analysis (27.6% in R1 versus 45.6% in R0, p = 0.026, and 37.2% in non-DHGP versus 59.2% in DHGP, p = 0.013), whereas non-DHGP but not R1 remained associated with worse prognosis in multivariate analysis. In patients with non-DHGP, R1 margin has no prognostic impact.

CONCLUSIONS

In patients undergoing resection of CRLMs, the prognostic value of poor tumor biology, such as in patients with non-DHGP, exceeds that of surgical radicality.

Incidental finding of solitary fibrous tumor of male breast: case report and review of literature

Solitary fibrous tumor (SFT) of the breast is a rare mesenchymal tumor composed of spindle-shaped tumor cells with collagen and large blood vessels in the shape of a "staghorn". It is discovered anywhere in the human body, usually incidentally or through nonspecific symptoms. A combination of clinical, histological, and immunohistochemical features is required to establish a diagnosis. There are no proper guidelines for the treatment of SFTs because of their rarity; however, wide surgical excision remains the "gold standard". A multidisciplinary team approach is recommended. They are mostly benign with a 5-year survival rate of 89%. Following a PubMed-indexed English literature review, only six publications presenting nine cases of breast SFT in a male patient were found. The following is the case of a 73-year-old man who presented with dry cough. A SFT in the right breast was discovered incidentally during the investigative work up, and the patient was referred to our Breast Clinic at the Jules Bordet Institute, Brussels, Belgium, for appropriate treatment. The patient's presentation, imaging, and histological sample all supported the diagnosis, and he underwent uneventful surgical resection. Here, we present the first case of an incidental finding of a SFT of the male breast, with its diagnosis and therapeutic challenges.

Circulating Tumor DNA After Neoadjuvant Chemotherapy in Breast Cancer Is Associated With Disease Relapse

PURPOSE

Detection of circulating tumor DNA (ctDNA) after neoadjuvant chemotherapy in patients with early-stage breast cancer may allow for early detection of relapse. In this study, we analyzed ctDNA using a personalized, tumor-informed multiplex polymerase chain reaction-based next-generation sequencing assay.

METHODS

Plasma samples (n = 157) from 44 patients were collected before neoadjuvant therapy (baseline), after neoadjuvant therapy and before surgery (presurgery), and serially postsurgery including a last follow-up sample. The primary end point was event-free survival (EFS) analyzed using Cox regression models.

RESULTS

Thirty-eight (86%), 41 (93%), and 38 (86%) patients had baseline, presurgical, and last follow-up samples, respectively. Twenty patients had hormone receptor-positive/human epidermal growth factor receptor 2-negative, 13 had triple-negative breast cancer, and 11 had human epidermal growth factor receptor 2-positive disease. Baseline ctDNA detection was observed in 22/38 (58%) patients and was significantly associated with Ki67 > 20% (P = .036) and MYC copy-number gain (P = .0025, false discovery rate = 0.036). ctDNA detection at presurgery and at last follow-up was observed in 2/41 (5%) and 2/38 (5%) patients, respectively. Eight relapses (seven distant and one local) were noted (median follow-up 3.03 years [range, 0.39-5.85 years]). After adjusting for pathologic complete response (pCR), ctDNA detection at presurgery and at last follow-up was associated with shorter EFS (hazard ratio [HR], 53; 95% CI, 4.5 to 624; P < .01, and HR, 31; 95% CI, 2.7 to 352; P < .01, respectively). Association between baseline detection and EFS was not observed (HR, 1.4; 95% CI, 0.3 to 5.9; P = .67).

CONCLUSION

The presence of ctDNA after neoadjuvant chemotherapy is associated with relapse in early-stage breast cancer, supporting interventional trials for testing the clinical utility of ctDNA monitoring in this setting.

Abstract P1-02-09: Results of a worldwide survey on the currently used histopathological diagnostic criteria for invasive lobular breast cancer (ILC)

Background. ILC represents the second most common histological type of breast cancer (BC), accounting for approximately 15% of all invasive BCs. Loss of cell-cell adhesion due to genomic alterations of CDH1,. the gene coding for E-cadherin, is the hallmark of ILC. So far, in the WHO guidelines, it is essential to recognize the dispersed or linear discohesive cells but it is not mandatory to demonstrate E-cadherin loss by immunohistochemistry (IHC) for diagnosing ILC. Recent central pathology revisions of clinical trials have demonstrated overdiagnosis of ILC in local pathological diagnosis, as only ~60% of the locally diagnosed ILCs were confirmed by central pathology. To understand the possible underlying reasons, we undertook a worldwide survey on the currently used histopathological diagnostic criteria for ILC. Materials and Methods. A survey was drafted using the online tool SurveyMonkey by a panel of pathologists and researchers from the European Lobular Breast Cancer Consortium (ELBCC). This survey was circulated to pathologists from December 14, 2020 until July, 1 2021. The main goals were to register the use of E-cadherin as a diagnostic marker for ILC and the systematic reporting of the ILC subtypes. Results. A total of 149 entries were recorded from 34 different countries from 6 continents. Pathologists declared working in a large tertiary (30%, 44/149) or university hospital (56%, 84/149), with an average yearly volume of BC samples &gt;300 in 111/149 (74%) and &gt;500 in 80/149 (54%) respondents. 117/149 (79%) are specialized in breast pathology. About half of the pathologists systematically perform IHC for ILC diagnosis (52%, 77/149), whilst others only perform staining in case of doubt (43%, 64/149) or for differentiating DCIS from LCIS (3%, 4/149). There was no association between the systematic use of IHC, the volume of BC samples, the type of institution (academic, large tertiary, private), and the number of pathologists in the institution. Concerning the use of IHC, 141/145(97%) participants use E-cadherin, 35/145 (24%) use β-catenin and 49/145 (34%) use p120-catenin. The majority (50%, 73/145) uses only E-cadherin, 13% (19/145) use E-cadherin in combination with β-catenin or 23% (33/145) use E-cadherin with p120-catenin, while 11% (16/145) use all 3 antibodies. For E-cadherin, 11 different clones were reported, of which the NCH-38 is the most frequently used (45%, 39/86), followed by Clone 36 (17%, 15/86) and EP700Y (16%, 14/86). Heterogeneity is reported regarding the used concentration per clone. The most frequently used modality of antigen retrieval is the heat induced one. Similar findings were observed for β-catenin and p120-catenin with each 4 different clones reported, again with variable concentrations. Only 4/104 (4%) respondents reported to perform DNA sequencing for CDH1 for diagnosing ILC. Most special lobular types are systematically reported by the vast majority of the pathologists: classic (149/149, 100%), pleomorphic (140/149, 94%), solid (108/149, 72%), histiocytoid/apocrine (90/149, 60%), alveolar (90/149, 60%), trabecular (54/149, 36%), mixed non-classic (54/149, 36%) and mucinous (51/149, 34%). Conclusions. We report the results of the first worldwide survey concerning diagnosis of ILC in pathological practice. The results demonstrate that ~half of the institutions systematically perform E-cadherin IHC to support the diagnosis of ILC. There is a great variability in E-cadherin antibody clones used as well as their concentrations, which might result in differences in staining results and their interpretation. As ILC-specific therapeutic avenues are currently being explored, some of which already in the context of clinical trials, it is of utmost importance to further improve the standardization of ILC diagnosis at the pathology level.

Citation Format: Maxim De Schepper, Anne Vincent-Salomon, Matthias Christgen, Karen Van Baelen, Hitoshi Tsuda, Sasagu Kurozumi, Maria Jose Brito, Gabor Cserni, Stuart Schnitt, Denis Larsimont, Janina Kulka, Pedro Luis Fernandez, Paula Rodriguez, Ana Aula, Cristina Mendelez, Mieke Van Bockstal, Aniko Kovacs, Zsuzsanna Varga, Jelle Wesseling, Rohit Bhargava, Pia Boström, Camille Franchet, Blessing Zambuko, Gustavo Matute, Anca Berghian, Paul van Diest, Steffi Oesterreich, Patrick WB Derksen, Giuseppe Floris, Christine Desmedt. Results of a worldwide survey on the currently used histopathological diagnostic criteria for invasive lobular breast cancer (ILC) [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P1-02-09.

Abstract P1-05-03: Integrating spatial transcriptomics and high-resolution morphological annotation to investigate tumor heterogeneity and PAM50 molecular subtyping in lobular breast cancer

Background: Invasive lobular breast carcinoma (ILC) represents 5 to 15% of all invasive breast cancers (BCs). Here, we aim to investigate inter- and intra-tumor heterogeneity in terms of microenvironment composition, PAM50 molecular classification and proliferation (genomic grade index [GGI]) by combining spatial transcriptomics (ST) and accurate morphological annotation. Methods: Spatial RNA sequencing (Visium - 10X Genomics) was performed on frozen tumor samples from 15 primary estrogen receptor positive, HER2-negative ILC patients with long-term follow up. Hematoxylin/eosin slides were morphologically annotated integrating manual and machine learning-based approaches reaching single-cell resolution (QuPath software). The relative histomorphological categories (HC) composition of each spot across the ST slide was computed as percentage of pixels, while the level of proximity of different HC was evaluated computing the proportion of co-occurring HC at each spot. The PAM50 subtypes (AIMS R package) and GGI were computed on spots containing at least 40% of tumor (merging all the spots belonging to each sample [pseudo-bulk] for PAM50, while calculating mean and standard deviation [SD] across spots for GGI). PAM50 was also computed on the pseudo-bulk of the whole set of spots per sample. Wilcoxon and Spearman rank tests were used to compare continuous variables and assess correlations. Results: Out of 15 tumors, 7 were T2 or T3, 6 were node positive at diagnosis and 14 were grade 2. Four patients experienced disease relapse. Morphological annotation revealed that an average (per patient) of 20.3% (5.6-46.7%), 65.9% (45.5-83.5%) and 6.5% (0.0-27.1%) of the spots corresponded to tumor, stroma and fat tissue respectively. Larger tumors (T2-3 vs T1) presented a higher proportion of fat tissue and tumor cells, although these differences did not reach statistical significance. The levels and spatial variability of proliferation, measured using GGI, were higher in T2-3 compared to T1 tumors (p = 0.072 and 0.040, respectively). Of note, higher spatial variability of proliferation was also associated with node-positive tumors (p = 0.066). By computing the PAM50 classification using the pseudo-bulk, 9 samples were classified as luminal A, 1 as luminal B and 5 as normal-like. Of interest, when focusing on the tumor enriched spots, 60% of the samples previously classified as normal-like were re-classified as luminal A. Samples from patients who relapsed showed a higher fraction of fat tissue at the level of the whole slide (14.4% vs 3.5%; p = 0.018), with an increased co-localization of fat tissue and tumor cells at the spot level as well as higher proliferation values, although not significant. Conclusions: High proportion of fat tissue together with higher co-localization of fat tissue with tumor cells are associated with poor outcome in ILC. Higher spatial variability of proliferation is associated with larger tumors, lymph node positivity and recurrence. The proportion of stroma and fat tissue affected substantially the PAM50 classification of the tumors. Further validation is needed.

Citation Format: Matteo Serra, Laetitia Collet, Mattia Rediti, Frédéric Lifrange, David Venet, Xiaoxiao Wang, Delphine Vincent, Ghizlane Rouas, Danai Fimereli, David Gacquer, Andrea Joaquin Garcia, Isabelle Veys, Ligia Craciun, Denis Larsimont, Miikka Vikkula, François Duhoux, Françoise Rothé, Christos Sotiriou. Integrating spatial transcriptomics and high-resolution morphological annotation to investigate tumor heterogeneity and PAM50 molecular subtyping in lobular breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P1-05-03.

Abstract PD14-05: Portraying tumor evolution of lobular breast cancer through phylogenetic analysis

Background: Despite therapeutic advancements, a substantial number of patients with treated early-stage invasive lobular carcinoma (ILC) of the breast will still relapse as late as 20 years after the initial tumor diagnosis, thus making follow-up a challenging task. Here, using patient-matched primary and metastatic tumors from patients with ILC, we aimed to decipher the evolution of lobular breast cancer through time and explore metastatic dissemination events and underlying heterogeneity. Materials and Methods: We retrospectively identified 38 patients with metastatic ILC, of which 6 with de novo metastatic disease. In total, 99 formalin-fixed paraffin embedded tissue samples of primary tumor and metastasis, together with well-annotated clinicopathological data, were available. Low coverage whole-genome sequencing was performed to infer somatic copy number aberrations (CNA). Phylogenetic reconstruction was performed with Integer Linear Program for the Copy-Number Tree Problem algorithm. Results: Reconstruction of the phylogenetic trees showed different patterns of dissemination. For patients with multiple metastatic samples sequenced (4/4 patients), the metastases were found to be seeded from a common metastatic precursor. For a subset of patients with multiple primaries (5/10 patients), distant metastases were seeded from specific clones inside the primary tumor. Detailed analysis of known driver genes showed that alterations in common driver genes such as TP53, MYC and CCND1 were shared between primary tumor and metastases in a large proportion of the patients (47%, 32% and 21% of patients respectively) whilst CNA in other driver genes including FGFR2, PTEN or AKT2 among others, were frequently private in the metastases. Interestingly, we observed that in approximately 30% of the patients, the metastases harbored less CNA than the matched primary tumor, resulting in shorter metastatic branches and possibly indicating a decelerated tumor progression. Further analysis of the genomic and clinicopathological characteristics showed that these patients were mostly de novo metastatic (p-value=0.002), metastasizing primarily to the liver or bone and had significantly more aberrations in NF1, AKT1 and FGFR (p-value=0.04, 0.01 and 0.03 respectively), when compared to the rest of the cohort. Finally, most of the patients (63%) had a lower number of CNA accumulated after the metastatic lineage separation compared to the common trunk, implying a late dissemination event. Conclusions: In this study, we described different metastatic dissemination events taking place in ILC. Our analyses allowed us to identify a subset of tumors characterized by slow tumor progression, indicating potential tumor dormancy, as well as evidence of late dissemination evidence for most of the patients, thus highlighting the importance of early detection through cancer screening. These findings further shed light on how ILCs evolves through time and could potentially influence the clinical management of invasive lobular breast cancer.

Citation Format: Danai Fimereli, David Venet, Mattia Rediti, David N Brown, Bram Boeckx, Marion Maetens, Samira Majjaj, Ghizlane Rouas, Maria Capra, Giuseppina Bonizzi, Federica Contaldo, Christine Galant, Martine Piccart, Giancarlo Pruneri, Denis Larsimont, Diether Lambrechts, Christine Desmedt, Françoise Rothé, Christos Sotiriou. Portraying tumor evolution of lobular breast cancer through phylogenetic analysis [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr PD14-05.

Abstract P2-01-06: Detection of circulating tumor DNA post neoadjuvant chemotherapy using a personalized assay is associated with disease relapse

Background: Approximately 30% of patients with early breast cancer present disease relapse after surgery, and technologies that enable the detection of circulating tumor DNA (ctDNA) were shown to identify them earlier than standard imaging. In the present study, we aimed to interrogate the value of the SignateraTM personalized ctDNA assay for early detection of disease relapse. Methods: The study included 52 early breast cancer patients undergoing neoadjuvant chemotherapy from an ongoing translational, single-center study at Jules Bordet Institute, Brussels, Belgium. From each patient, primary tumor tissue sections, blood sample for normal DNA, and serial plasma samples were sent to NATERA Inc for ctDNA detection using the SignateraTM assay. Plasma samples were collected before the initiation of neoadjuvant chemotherapy (baseline), after neoadjuvant chemotherapy, before surgery (pre-surgery), and at follow-up post-surgery. Whole exome sequencing (WES) was performed on the primary tumor tissue and matched normal DNA to design a patient-specific ctDNA assay. The unique set of SNV’s identified in WES were tracked in serial plasma samples. Associations between baseline ctDNA detection and standard clinicopathological characteristics and primary tumor point mutations or copy number aberrations were evaluated. Association between ctDNA detection, pathological complete response (pCR) and event-free survival (EFS) were explored. Fisher, Mann-Whitney and Kruskal-Wallis tests were used to compare variables. Log-rank tests and Cox regressions were used for survival analyses. Hazard ratios (HRs) and confidence intervals (CIs) were obtained from Cox regressions. For multivariable tests, logistic regressions were used for binary outcomes and Cox regressions for survival outcomes. P-values were obtained by comparing models with and without the variable of interest using Chi-square test in ANOVAs. Results: Forty-four out of 52 (85%) initially selected patients had the required tumor cellularity (≥ 20%) and adequate tumor DNA quantity and quality and had personalized ctDNA assays designed. In these 44 patients, 154 plasma samples were successfully processed including 38, 41, 75, 38 at baseline, pre-surgery, follow-up (any timepoint) and last follow-up timepoint, respectively. Twenty (45%) patients had hormone receptor positive/HER2-negative, 13 (30%) triple-negative and 11 (25%) HER2-positive breast cancers. Detection of ctDNA was observed in 22 of 38 (58%) patients at baseline and was significantly associated with Ki67&gt;20% and MYC copy number gain in the primary tumor. ctDNA detection at pre-surgery and at last follow-up was observed in 2 of 41 (5%) and 2 of 38 (5%) patients respectively. All patients who achieved pCR were ctDNA-negative at the pre-surgical time point. With a median follow-up of 3.03 years (range 0.39 - 5.85), we observed 8 relapses (7 distant and 1 local, respectively). After adjusting for pCR, ctDNA detection was associated with shorter EFS at pre-surgery and at last follow-up time points (HR: 53, 95% CI: 4.5-624, p&lt;0.01, and HR: 31, 95% CI: 2.7-352, p&lt;0.01, respectively), but not at baseline (HR: 1.4, 95% CI: 0.3-5.9, p=0.67). Conclusions: The detection of ctDNA post neoadjuvant chemotherapy is associated with disease relapse in early breast cancer supporting interventional trials in this setting.

Citation Format: Elisa Agostinetto, Frédéric Cailleux, Matteo Lambertini, Françoise Rothé, Hsin-Ta Wu, Mustafa Balcioglu, Himanshu Sethi, Delphine Vincent, Giulia Viglietti, Andrea Gombos, Andreas Papagiannis, Isabelle Veys, Ahmad Awada, Christos Sotiriou, Ekaterina Kalashnikova, Alexey Aleshin, Denis Larsimont, David Venet, Michail Ignatiadis. Detection of circulating tumor DNA post neoadjuvant chemotherapy using a personalized assay is associated with disease relapse [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-01-06.

Abstract PD14-02: Unravelling spatial tumor organization and heterogeneity in lobular breast cancer using spatial transcriptomics

Introduction: Invasive lobular breast cancer (ILC) is the most frequent special type of breast cancer. Recent studies showed the impact of intratumor heterogeneity (ITH) on patient outcome. Here, we aimed to better characterize ITH in ILC using spatial transcriptomics (ST) together with high-resolution morphological annotation. Methods: Spatial transcriptomics (Visium 10x Genomics) was performed on frozen tumor samples from 15 primary estrogen receptor positive, HER2-negative ILCs with 4 patients developing disease relapse. For each sample, we annotated hematoxylin/eosin sections (QuPath software) in two steps: manual annotation of specific histomorphological structures (e.g. normal breast ducts, fat tissue, vessels) and machine learning annotation of stroma and tumor cells at the single cell level. Proportion of each specific tissue type per sample was defined by pixel percentage computed within each ST spot. For each sample, the proportion of a given tissue type was defined as the proportion of pixels annotated with this specific type averaged across all spots within the tissue section. Spatially variable genes were used as input for non-negative matrix factorization and the reduced expression matrix was clustered with the Louvain algorithm implemented in Seurat. A cluster of spots was defined as tumoral if the average proportion of pixels annotated as tumor across its constitutive spots was higher than the average proportion of tumor pixels across all spots from the tissue section. Cluster characterization was performed using gene set enrichment analysis based on hallmarks (Molecular Signature Database) with a false discovery rate &lt; 0.05. Spatial heterogeneity and tumor organization within each sample were assessed according to the number and type of cluster interactions, homo-contacts being defined as interactions between spots belonging to the same cluster and hetero-contacts between spots from two different clusters. Comparisons between groups were assessed using Wilcoxon test. Results: A total of 45 tumor clusters were identified among the 15 patients, with a range of 2-4 tumor clusters per sample highlighting intra-tumor heterogeneity. Cluster characterization revealed the presence of clusters enriched in different biological pathways within a given sample. These analyses also showed inter-patient heterogeneity as witnessed by distinct tumor clusters only present in a subset of tissue samples. In particular, 66% (N=10/15) of the tissue samples harbored clusters enriched in oxidative phosphorylation, 53% (N=8/15) in epithelial-mesenchymal transition, 33% (N=5/15) in interferon gamma response, 27% (N=4/15) in TNF-alpha via NFkB, 27% (N=4/15) in androgen response and 13% (N=2/15) in protein secretion hallmarks. All samples shared at least one tumor cluster enriched in estrogen early and late response.Although the number of tumor clusters was similar between samples from patients with or without relapse (median of 3, range 2-4), the presence of clusters enriched in protein secretion was associated with disease recurrence (p = 0.02). Of note, higher number of hetero-contacts mirroring tumor disorganization was associated with poor outcome although not significant (p= 0.08). Conclusions: Here, we showed for the first time a substantial inter- and intra-tumor heterogeneity of ILC at an unprecedented level, characterized by the presence of specific tumor clusters and distinct tumor organization patterns associated with outcome. We also. uncovered potentially targetable clusters missed by bulk analysis, offering novel perspectives for optimized ILC care. Further validation is warranted.

Citation Format: Laetitia Collet, Matteo Serra, Mattia Rediti, Frédéric Lifrange, David Venet, XiaoXiao Wang, Delphine Vincent, Ghizlane Rouas, Danai Fimereli, David Gacquer, Andrea Joaquin Garcia, Isabelle Veys, Ligia Craciun, Denis Larsimont, Miikka Vikkula, François Duhoux, Françoise Rothé, Christos Sotiriou. Unravelling spatial tumor organization and heterogeneity in lobular breast cancer using spatial transcriptomics [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr PD14-02.

Results of a worldwide survey on the currently used histopathological diagnostic criteria for invasive lobular breast cancer

Invasive lobular carcinoma (ILC) represents the second most common subtype of breast cancer (BC), accounting for up to 15% of all invasive BC. Loss of cell adhesion due to functional inactivation of E-cadherin is the hallmark of ILC. Although the current world health organization (WHO) classification for diagnosing ILC requires the recognition of the dispersed or linear non-cohesive growth pattern, it is not mandatory to demonstrate E-cadherin loss by immunohistochemistry (IHC). Recent results of central pathology review of two large randomized clinical trials have demonstrated relative overdiagnosis of ILC, as only ~60% of the locally diagnosed ILCs were confirmed by central pathology. To understand the possible underlying reasons of this discrepancy, we undertook a worldwide survey on the current practice of diagnosing BC as ILC. A survey was drafted by a panel of pathologists and researchers from the European lobular breast cancer consortium (ELBCC) using the online tool SurveyMonkey®. Various parameters such as indications for IHC staining, IHC clones, and IHC staining procedures were questioned. Finally, systematic reporting of non-classical ILC variants were also interrogated. This survey was sent out to pathologists worldwide and circulated from December 14, 2020 until July, 1 2021. The results demonstrate that approximately half of the institutions use E-cadherin expression loss by IHC as an ancillary test to diagnose ILC and that there is a great variability in immunostaining protocols. This might cause different staining results and discordant interpretations. As ILC-specific therapeutic and diagnostic avenues are currently explored in the context of clinical trials, it is of importance to improve standardization of histopathologic diagnosis of ILC diagnosis.

A Pathologist-Annotated Dataset for Validating Artificial Intelligence: A Project Description and Pilot Study

Purpose:

Validating artificial intelligence algorithms for clinical use in medical images is a challenging endeavor due to a lack of standard reference data (ground truth). This topic typically occupies a small portion of the discussion in research papers since most of the efforts are focused on developing novel algorithms. In this work, we present a collaboration to create a validation dataset of pathologist annotations for algorithms that process whole slide images. We focus on data collection and evaluation of algorithm performance in the context of estimating the density of stromal tumor-infiltrating lymphocytes (sTILs) in breast cancer.

Methods:

We digitized 64 glass slides of hematoxylin- and eosin-stained invasive ductal carcinoma core biopsies prepared at a single clinical site. A collaborating pathologist selected 10 regions of interest (ROIs) per slide for evaluation. We created training materials and workflows to crowdsource pathologist image annotations on two modes: an optical microscope and two digital platforms. The microscope platform allows the same ROIs to be evaluated in both modes. The workflows collect the ROI type, a decision on whether the ROI is appropriate for estimating the density of sTILs, and if appropriate, the sTIL density value for that ROI.

Results:

In total, 19 pathologists made 1645 ROI evaluations during a data collection event and the following 2 weeks. The pilot study yielded an abundant number of cases with nominal sTIL infiltration. Furthermore, we found that the sTIL densities are correlated within a case, and there is notable pathologist variability. Consequently, we outline plans to improve our ROI and case sampling methods. We also outline statistical methods to account for ROI correlations within a case and pathologist variability when validating an algorithm.

Conclusion:

We have built workflows for efficient data collection and tested them in a pilot study. As we prepare for pivotal studies, we will investigate methods to use the dataset as an external validation tool for algorithms. We will also consider what it will take for the dataset to be fit for a regulatory purpose: study size, patient population, and pathologist training and qualifications. To this end, we will elicit feedback from the Food and Drug Administration via the Medical Device Development Tool program and from the broader digital pathology and AI community. Ultimately, we intend to share the dataset, statistical methods, and lessons learned.

Fluorescent Multiplex Immunohistochemistry Coupled With Other State-Of-The-Art Techniques to Systematically Characterize the Tumor Immune Microenvironment

Our expanding knowledge of the interactions between tumor cells and their microenvironment has helped to revolutionize cancer treatments, including the more recent development of immunotherapies. Immune cells are an important component of the tumor microenvironment that influence progression and treatment responses, particularly to the new immunotherapies. Technological advances that help to decipher the complexity and diversity of the tumor immune microenvironment (TIME) are increasingly used in translational research and biomarker studies. Current techniques that facilitate TIME evaluation include flow cytometry, multiplex bead-based immunoassays, chromogenic immunohistochemistry (IHC), fluorescent multiplex IHC, immunofluorescence, and spatial transcriptomics. This article offers an overview of our representative data, discusses the application of each approach to studies of the TIME, including their advantages and challenges, and reviews the potential clinical applications. Flow cytometry and chromogenic and fluorescent multiplex IHC were used to immune profile a HER2+ breast cancer, illustrating some points. Spatial transcriptomic analysis of a luminal B breast tumor demonstrated that important additional insight can be gained from this new technique. Finally, the development of a multiplex panel to identify proliferating B cells, Tfh, and Tfr cells on the same tissue section demonstrates their co-localization in tertiary lymphoid structures.

Functional Th1-oriented T follicular helper cells that infiltrate human breast cancer promote effective adaptive immunity

We previously demonstrated that tumor-infiltrating lymphocytes (TIL) in human breast cancer sometimes form organized tertiary lymphoid structures (TLS) characterized by CXCL13-producing T follicular helper (Tfh) cells. The present study found that CD4+ Tfh TIL, CD8+ TIL, and TIL-B, colocalizing in TLS, all express the CXCL13 receptor CXCR5. An ex vivo functional assay determined that only activated, functional Th1-oriented Tfh TIL (PD-1hiICOSint phenotype) provide help for immunoglobulin and IFN-γ production. A functional Tfh TIL presence signals an active TLS, characterized by humoral (immunoglobulins, Ki-67+ TIL-B in active germinal centers) and cytotoxic (GZMB+CD8+ and GZMB+CD68+ TIL plus Th1 gene expression) immune responses. Analysis of active versus inactive TLS in untreated patients revealed that the former are associated with positive clinical outcomes. TLS also contain functional T follicular regulatory (Tfr) TIL, which are characterized by a CD25+CXCR5+GARP+FOXP3+ phenotype and a demethylated FOXP3 gene. Functional Tfr inhibited functional Tfh activities via a glycoprotein A repetitions predominant (GARP)-associated TGF-β-dependent mechanism. The activity of tumor-associated TLS was dictated by the relative balance between functional Tfh TIL and functional Tfr TIL. These data provide mechanistic insight into TLS processes orchestrated by functional Th1-oriented Tfh TIL, including TIL-B and CD8+ TIL activation and immunological memory generation. Tfh TIL, regulated by functional Tfr TIL, are an expected key target of PD-1/PD-L1 blockade.

Circulating Tumor DNA to Interrogate the Safety of Letrozole-Associated Controlled Ovarian Stimulation for Fertility Preservation in Breast Cancer Patients

Background

Current fertility preservation strategies for young breast cancer patients planning a future motherhood include the association of controlled ovarian stimulation with the aromatase inhibitor letrozole (let-COS) to harvest mature oocytes while maintaining low estradiol levels. Despite this is a widely adopted protocol, the safety of let-COS on breast cancer outcomes has been poorly investigated and its use remains off-label. We assessed the safety of let-COS in breast cancer patients using circulating tumor DNA (ctDNA) as a surrogate biomarker of disease recurrence.

Methods

BROVALE is an interventional non-randomized prospective study designed to evaluate the efficacy and safety of let-COS for fertility preservation in early breast cancer patients before starting (neo)adjuvant chemotherapy. Letrozole was administered throughout the COS cycle, until ovulation triggering. Safety was a secondary endpoint. Data on oncological outcomes were collected during the follow-up as well as plasma and whole blood for evaluation of ctDNA levels at the time of enrollment (i.e. before starting let-COS) and oocyte retrieval (i.e. 48 hours after the last administration of letrozole). Targeted gene sequencing on the primary tumor samples was performed to identify specific mutations used for ctDNA analysis by digital PCR. DNA extracted from whole blood samples was used to discriminate between somatic and germline mutations.

Results

From April 2014 to May 2017, 29 young early breast cancer patients enrolled in the BROVALE study who had available tissue samples participated to the ctDNA substudy. Among them, 15 had at least one validated somatic mutation. ctDNA was undetectable neither before nor after let-COS in 9 of them. Six patients had detectable ctDNA in the plasma samples collected before Let-COS. No change in ctDNA level after let-COS was observed in 3 patients and the level decreased (fold-change ≤ 0.5) in two women. One patient experienced an increased (fold-change ≥ 2) in ctDNA level but without disease relapse 34 months after diagnosis.

Conclusions

No increase in ctDNA level was observed in 93% (14/15) of the patients receiving let-COS supporting its use as a safe strategy for young women with early breast cancer interested in fertility preservation before chemotherapy.

Neo-CheckRay: radiation therapy and adenosine pathway blockade to increase benefit of immuno-chemotherapy in early stage luminal B breast cancer, a randomized phase II trial

BACKGROUND

Residual breast cancer after neo-adjuvant chemotherapy (NACT) predicts disease outcome and is a surrogate for survival in aggressive breast cancer (BC) subtypes. Pathological complete response (pCR) rate, however, is lower for luminal B BC in comparison to the triple negative (TNBC) and HER2+ subtypes. The addition of immune checkpoint blockade (ICB) to NACT has the potential to increase pCR rate but is hampered by the lower immunogenicity of luminal B BC. Novel strategies are needed to stimulate the immune response and increase the response rate to ICB in luminal B BC.

METHODS

The Neo-CheckRay trial is a randomized phase II trial investigating the impact of stereotactic body radiation therapy (SBRT) to the primary breast tumor in combination with an anti-CD73 (oleclumab) to increase response to anti PD-L1 (durvalumab) and NACT. The trial is designed as a three-arm study: NACT + SBRT +/- durvalumab +/- oleclumab. The result at surgery will be evaluated using the residual cancer burden (RCB) index as the primary endpoint. Six patients will be included in a safety run-in, followed by a randomized phase II trial that will include 136 evaluable patients in 3 arms. Inclusion is limited to luminal B breast cancers that are MammaPrint genomic high risk.

DISCUSSION

combination of ICB with chemotherapy in luminal B BC might benefit from immune priming agents to increase the response rate. As none have been identified so far, this phase II trial will evaluate SBRT and oleclumab as potential immune priming candidates.

TRIAL REGISTRATION

trial registered on ClinicalTrials.gov ( NCT03875573 ) on March 14th, 2019.

Abstract 182: Recapitulating spatial tumor morphology using automated classifier in triple negative breast cancer

Introduction Triple negative breast cancer (TNBC) is a heterogeneous disease. Spatial transcriptomics (ST) interrogates gene expression in spatially defined spots. Here, we assessed whether ST expression data could identify specific histomorphologic features from TNBC samples, the ultimate goal being to develop a tool allowing to automatically annotate ST slides from gene expression data.

Methods ST expression profiles were obtained from 41 TNBC samples. T and B cell immune phenotyping was performed on a consecutive slide using double CD3/CD20 IHC. All samples were manually annotated in 11 histomorphological categories (see Table). ST spots with artifacts or less than 500 reads were removed from the analysis. Each spot was assigned to its most common annotation. A linear booster classifier was used to classify the spots into 11 histomorphological categories based on gene expression. Classification accuracy was summarized by area under the ROC curve (AUC), assessed using leave-a-patient-out (LPO) or in-patient 10-fold cross-validation (xVal).

Results Most ST spots were annotated as invasive tumor and stroma with low TILs as well stroma with high TILs (see Table). Overall, the performance of the classifier was very high. However, xVal method obtained higher AUC than the LPO method, reflecting higher interpatient than intrapatient variations. Necrosis, in situ carcinoma and B cells were very variable between patients, but not intrapatient, as shown by low LPO and high xVal AUCs. Of note, misclassification of B cells could be due to poor distinction of B vs T cells on HE slides despite IHC support. Spots with multiple annotations were also more difficult to classify.

Conclusion Here, we developed a high-performance classifier based on the biggest series of ST data allowing to identify several histomorphological features from TNBC tissues, representing a unique tool for further ST research.

SupercategoriesCategoriesAbbreviationsN spotsN samplesAUC LPO (%)AUC Xval (%)StromaStroma220484180.292.5Stroma with low TILslow sTILs140924178.291.8Stroma with high TILshigh sTILs75543984.394.8Blood vesselsBV1912774.283.6Lymphoid nodulesLN185148994.9High lymphocytes B areasBcell26564.495.9Invasive tumorIT126364088.894.7Invasive tumor with low or no intratumoral TILslow iTILs101773987.594.6Invasive tumor with high intratumoral TILshigh iTILs24592484.897.1OthersFat tissuesFT27212292.897.4NecrosisN10621975.295.4In situ carcinomaIS289749.399.1Normal glandsNG1741686.794.4

Citation Format: Xiaoxiao Wang, David Venet, Floriane Dupont, Ghizlane Rouas, Linnea Stenberg, Annelie Mollbrink, Denis Larsimont, Joakim Lundeberg, Françoise Rothé, Christos Sotiriou. Recapitulating spatial tumor morphology using automated classifier in triple negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 182.

Abstract 609: Contribution of the tumor and stroma compartments for TNBC molecular classification using spatial transcriptomics analysis

Introduction Triple negative breast cancer (TNBC) is a heterogeneous disease associated at least with five distinct molecular subtypes namely basal like (BL), immunomodulatory (IM), luminal AR (LAR), mesenchymal (M) and mesenchymal-stem like (MSL). Spatial transcriptomics (ST) interrogates gene expression in spatially defined spots. Here, we aimed to assess the contribution of tumor and stroma compartments in defining each TNBC molecular subtype by comparing bulk tumor RNAseq, pseudo-bulk (PB) derived from ST, tumor and stroma ST spots.

Methods Spatially resolved gene expression profiles were obtained from 94 TNBC samples using ST, spots with artifacts or less than 500 reads being excluded from further analysis. Forty-one TNBC samples were manually annotated by a breast pathologist into 3 different classes: tumor, stroma and the rest. Manual histological annotation was used to build a classifier to assign each ST spot to tumor or stroma compartment. Bulk RNAseq data was obtained from consecutive sections for all tumors using RiboZero kit. PB profiles were obtained by summing the reads from all the spots of a given tumor, as well as from all spots classified as tumor and stroma compartment. A linear booster classifier was used to classify the spots based on gene expression. Each bulk and PB was assigned to one of 5 TNBC molecular subtypes.

Results PB data derived from ST analysis identified 18 BL, 26 IM, 10 LAR, 27 M and 13 MSL among the 94 TNBC tumor samples. An 87% concordance in the subtyping was observed between the bulk and PB data, with half of the discordant cases being between BL and IM subtypes. All LAR and BL tumors, as well as most M (96%) were consistently classified using tumor spots only whereas all MSL (100%) and the majority of LAR (91%) and IM (92%) samples were concordant using stroma spots only. In half of the IM samples, the signal derived from both the tumor and the stroma compartments while in the other half derived from the stroma. Misclassification mainly occurred between BL and IM subtypes, as well as between M and MSL. LAR subtype appeared to be the most stable one.

Conclusion The use of spatial transcriptomics allowed to show the relative contribution of the tumor and stroma compartments for TNBC molecular classification. The LAR, BL and M subtypes were driven by signals from the tumor compartment while MSL was driven by the stroma compartment. The IM signal was derived by both the tumor and stroma compartments.

Citation Format: David Venet, Xiaoxiao Wang, Floriane Dupont, Ghizlane Rouas, Linnea Stenbeck, Annelie Mollbrink, Denis Larsimont, Joakim Lundeberg, Françoise Rothé, Christos Sotiriou. Contribution of the tumor and stroma compartments for TNBC molecular classification using spatial transcriptomics analysis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 609.

Infiltrative tumour growth pattern correlates with poor outcome in oesophageal cancer

Objective

Oesophageal cancer (OEC) is an aggressive disease with a poor survival rate. Prognostic markers are thus urgently needed. Due to the demonstrated prognostic value of histopathological growth pattern (HGP) in other cancers, we performed a retrospective assessment of HGP in patients suffering from invasive OEC.

Design

A first cohort composed of 89 treatment-naïve operated patients with OEC from The Cancer Genome Atlas (TCGA) public database was constituted, from which H&E images and RNA-sequencing data were retrieved. Next, a second cohort composed of 99 patients with OEC treated and operated in a Belgian hospital was established. H&E-stained sections and extracted tumorous RNA were obtained from the samples. HGP were assessed on H&E slides as infiltrative (IGP) or expansive (EGP). TCGA RNA-sequencing data were analysed through the gene set enrichment analysis and Cytoscape softwares. Real-time quantitative PCR (qPCR) experiments were performed to assess gene expression in the Belgian cohort.

Results

IGP patients displayed a grim prognosis compared with EGP patients, while IGP was found as associated with numerous lymphovascular emboli and perinervous infiltrations. Analyses of the TCGA expression data showed that angiogenesis, epithelial-to-mesenchymal transition (EMT) and inflammation were significantly upregulated in IGP compared with EGP samples. qPCR experiments of three genes appearing as highly upregulated in each pathway showed no difference in expression according to the HGP.

Conclusion

The current study demonstrates the poor prognostic value carried by IGP in OC and suggests angiogenesis, EMT and inflammation as key carcinogenetic pathways upregulated in this pattern.