Invasive Lobular Carcinoma Research Articles

Abstract PS08-02: Efficacy of Sacituzumab-Govitecan (SG) post Trastuzumab-deruxtecan (T-DXd) and vice versa for HER2low advanced or metastatic breast cancer (MBC): a French multicentre retrospective study

Abstract Background: Based on ASCENT, TROPICS-02 and DESTINY-Breast04 trials, SG and T-DXd recently became approved for HER2low MBC. Since the payloads of both SG and T-DXd belong to the same cytotoxic class (topoisomerase-1 inhibitor), cross-resistance is a potential concern. However, no data is available on the efficacy of one antibody drug conjugate (ADC) after another and the best therapeutic sequence has not been evaluated yet. Methods: We conducted a retrospective study in 19 French comprehensive cancer centres. All patients (pts) with HR+ or HR- and HER2low MBC treated with SG followed, immediately or not, by T-DXd (or vice versa) were included. HR expression was defined on the last available tumor sample. The study primary objective was to report the second ADC (ADC2) progression-free survival (PFS) in the whole population. Secondary objectives included first ADC (ADC1) progression-free interval (PFI) and overall survival (OS) in the whole population and subgroup analyses by HR status. Results: The individual data of 126 eligible women were obtained from 19 participating centres. Median age was 54.5 years (range: 30-80y). N=110 (87.3%) pts had invasive carcinoma of not special type, N=12 (9.5%) invasive lobular carcinoma and 4 (3.2%) other histological subtype. N=87 (69%) and 39 (31%) had HR+/HER2low and HR-/HER2low MBC, respectively. N=16 patients were germline mutation carriers (BRCA1 N=7; BRCA2 N=6; other genes on HBOC panel N=3). ADC1 was given as a median of third (range: 1-10) line of chemotherapy and ADC2 as fifth (range: 2-12) line. A large majority (N=94, 74.6%) of pts received SG as ADC1 (N=82 with HR- and N=12 with HR+ MBC) while N=32 (25.4%) received T-DXd as ADC1 (N=27 with HR+ and n=5 with HR- MBC). 53.2% (N=67) received ADC1 immediately followed by ADC2 while 46.8% (N=59) received ADC2 after 1 (N=40) or 2 (N=12) or ≥ 3 (N=6) other lines of chemotherapy. N=19 (15.07%) and N=26 (20.63%) had a meningeal and/or cerebral metastasis at the time of the initiation of ADC1 and ADC2 respectively. After a median follow-up of 3 months, ADC2 was discontinued in 63 pts of which 51 (82.3%) for progression disease and 4 (6.5%) for toxicity due to T-DXd. Importantly, 50% of pts (N=63) were still under ADC2 at the time of this first analysis. The observed median PFS for ADC2 and median PFI for ADC1 are presented in the Table below: Median OS was not reached independently of the sub-populations of pts. Population and sequential regimen Median (mo) PFI ADC1 Median (mo) PFS ADC2 Whole population (N=126) SG → T-DXd (N=94) T-DXd→SG (N=32) 4.5 (95%CI [3.4-5.1]) 2.7 (95%CI [2.1-3.3] HR-/HER2low (N=82) having received SG as ADC1 then T-DXd as ADC2 4.8 (95%CI [3.8-5.1]) 3.3 (95%CI [2.5-3.7]) HR+/HER2low (n=27) having received T-DXd as ADC1 then SG as ADC2 2.7 (95%CI [2.0-3.2]) 2.0 (95%CI [1.6-NR]) Conclusion: To the best of our knowledge, this is the largest cohort evaluating the efficacy of subsequent ADCs administration in HER2low MBC. In these heavily pre-treated pts, subsequent use of ADCs seem to be associated with shortened PFS in both HR+/HR- subgroups, independently of their administration order. Data will be updated and completed for the meeting. Moreover, the number of eligible pts will be increased. Table 1: median TPP and PFS2 in whole population and HR subgroups Citation Format: François Poumeaud, Mathilde Morisseau, Luc Cabel, Anthony Gonçalves, Charlène Rivier, Olivier Trédan, Elsa Volant, Jean Sebastien FRENEL, Sylvain Ladoire, William Jacot, Mathieu Jamelot, Hervé Fokatichoue, Luis Teixeira, Francois-Clement Bidard, Delphine Loirat, Christelle Levy, Bastien Cabarrou, Antoine Deleuze, Elise Deluche, Thomas Grellety, Frédéric Fiteni, Hervé Bischoff, Roman Vion, Stéphanie Becourt, Thibaut Reverdy, Alexandre de Nonneville, Florence Dalenc. Efficacy of Sacituzumab-Govitecan (SG) post Trastuzumab-deruxtecan (T-DXd) and vice versa for HER2low advanced or metastatic breast cancer (MBC): a French multicentre retrospective study [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PS08-02.

Abstract PO2-16-12: Real world evidence of neoadjuvant chemotherapy for breast cancer treatment in a Brazilian multicenter cohort: correlation of pathological complete response and overall survival

Abstract Introduction: Breast cancer is the most common malignancy among women in Brazil and worldwide. Neoadjuvant chemotherapy (NAC) has been increasingly used for the treatment of breast cancer conditions ranging from locally advanced tumors to early-stage triple-negative and HER-2 positive tumors. Nowadays only 5% of breast cancer patients are enrolled in clinical trials. Real-world data is important to evaluate how clinical trial treatments behave in the real world with all the heterogeneous patient characteristics of those treated differently from the homogeneity of clinical trials. Objectives: To evaluate the rates of pathological complete response (pCR) in patients undergoing neoadjuvant chemotherapy (NAC) for the treatment of breast cancer (BC) To examine the differences in pathological complete response (pCR) rates between HER-2 positive breast cancer patients with and without trastuzumab treatment, and between triple-negative breast cancer (TNBC) patients with and without platinum-based treatment, Additionally, we aim to assess the impact of pCR on overall survival (OS) and disease-free survival (DFS) using real-world data (RWD). Methods: This was a retrospective, multicentric cohort study, that included female patients over 18 years of age, with a diagnosis of non-metastatic breast cancer undergoing NAC. As an exploratory real-world data study, no confirmatory hypothesis was established, so no corrections for multiple comparisons were necessary. Overall survival (OS) and disease-free survival (DFS) were estimated by the Kaplan-Meier method calculated at five years. Additionally, we conducted a multivariate analysis to identify significant associations with pathologic complete response (pCR) and overall survival (OS). We employed a forest plot to visually represent these associations Results: From 2011 to 2020, 1,891 patients were included in the study, and 421 (22,3%) achieved pCR (ypT0 ypN0) and considering the presence of residual in situ carcinoma (DCIS) the pCR was seen in 467 patients (23,5) without significant difference (p=0,567) . The pCR rate varied between the subtypes: luminal A 17,0%, luminal B 21,3%, luminal HER2 23,0%, TNBC 22,5% and HER2 28,5% (p = 0,057). The type of neoadjuvant chemotherapy (NAC) regimen was correlated with pathological complete response (pCR). Among HER2-positive patients, those who received Trastuzumab had a significantly higher rate of pCR compared to those who did not receive it (p < 0.0001). Similarly, in patients with TNBC, those who underwent treatment with platinum-based regimens also showed higher rates of pCR (p < 0.0001). There were 694 deaths, and the 5-year OS rate was 62.9%. OS was also grouped according to pCR status, and pCR OS rate was 88,3% and non-pCR 58.1% significant difference observed (p < 0.0001). Five-year DFS of pCR was 92.2% and non-pCR 64.3% (p < 0.0001). Conclusion: this real-world data study evaluated the rates of pathological complete response (pCR) in breast cancer patients undergoing neoadjuvant chemotherapy (NAC). The results revealed varying pCR rates among different breast cancer subtypes, with HER2-positive and triple-negative subtypes showing higher rates. The use of Trastuzumab in HER2-positive patients and platinum-based regimens in triple-negative patients correlated with significantly higher pCR rates. Furthermore, achieving pCR was associated with improved overall survival (OS) and disease-free survival (DFS). These findings emphasize the importance of considering individual tumor characteristics and tailoring treatment strategies for breast cancer patients to optimize outcomes. Clinicopathological characteristics of patients AJCC, American Joint Committee on Cancer; IDC, invasive ductal carcinoma; ILC, invasive lobular carcinoma; TNBC triple negative breast cancer. NAC schemas and correlation with pCR. AC-T, doxorubicin + cyclophosphamide – taxane; AC-TPlatinum, doxorubicin + cyclophosphamide – taxane+carboplatin; AC-TH, doxorubicin + cyclophosphamide – taxane+herceptin. Citation Format: Marcelo Antonini, Andre Mattar, Fernanda Grace Bauk Richter, Gabriel Pannain, Andressa Amorim, Marina Diogenes, Odair Ferraro, Luiz Gebrim, Reginaldo Coelho Lopes, Juliana Real. Real world evidence of neoadjuvant chemotherapy for breast cancer treatment in a Brazilian multicenter cohort: correlation of pathological complete response and overall survival [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-16-12.

Abstract PO5-08-05: Breast Cancer in PMS2 related Lynch Syndrome: evidence of a possible association?

Abstract Background: Lynch syndrome (LS) is a hereditary cancer predisposition syndrome caused by pathogenic variants (PVs) in mismatch repair genes, MLH1, MSH2, MSH6, and PMS2. LS is associated with increased risk of colorectal, and endometrial cancers but breast cancer risk is uncertain, with some studies suggesting MSH6 and PMS2 PVs may have a higher risk for breast cancer. Our study outlines the incidence and clinical characteristics of breast cancer in PMS2-related LS identified at a large academic center. Methods: Patients with PMS2 PVs identified between July 2009 and May 2023 were selected from a database at the Nancy and James Grosfeld Cancer Genetic Center at Beaumont Health. Data on demographics, genetic testing, cancer types, and breast cancer characteristics were retrospectively analyzed. Results: A total of 108 patients from 74 families were found to carry a pathogenic or likely pathogenic variant in PMS2, of whom the majority were female (75%) and Caucasian (85%). The median age at genetic testing was 52y (19 to 95y). The most common variant was c.137G > T (p.Ser46Ile), seen in 15 of 74 (20%) families. Forty-seven patients (46%) had a personal history of cancer, with a median age at diagnosis of 58y. Of these forty-seven patients, sixteen (34%) had multiple malignancies, including one patient with six separate cancers. The most common malignancies were breast (19; 40%), colon (16; 34%), followed by uterine cancer (7), pancreas (4), and prostate (3). The median age at breast cancer diagnosis was 53y, with a range of 41-78y. The most common histopathology was invasive ductal carcinoma (54%), followed by DCIS (31%), and invasive lobular carcinoma (15%). The majority of patients had breast tumors with stage 0 or 1 (75%), grade 2 (63%), ER-positive (92%), PR positive (67%), and HER2-negative (88%). One patient had triple-negative breast cancer. Sixty-seven percent of breast cancers were less than two centimeters, and 92% were lymph node-negative. Fifty-nine percent received radiation therapy and 53% received chemotherapy. Conclusion: Our study outlines the incidence and clinical characteristics of breast cancer in PMS2-related LS. Breast cancer was the most common malignancy in our cohort of PMS2 PV carriers, accounting for 40% of all cancers, supporting a possible association between PMS2 and breast cancer. The majority of PMS2-related breast cancers were invasive ductal type, early stage, intermediate grade, and hormone receptor-positive. Further studies with larger diverse cohorts of patients with LS are needed to better characterize a possible association in order to provide tailored breast cancer screening and management guidelines for this population. Citation Format: Ujjwal Karki, Tara Rangarajan, Dana Zakalik. Breast Cancer in PMS2 related Lynch Syndrome: evidence of a possible association? [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-08-05.

Abstract PO1-07-10: Blood Based Early Cancer Detection Assay

Abstract Background: Breast cancer screening programs utilizing mammography have been shown to be highly effective in identifying breast cancer in women over the age of 40. High breast density is an independent risk factor for breast cancer and makes mammograms more difficult to interpret, decreasing their sensitivity. In the spring of 2023, the FDA, who certifies all mammography facilities under the Mammography Quality Standards Act, updated its regulations to require that breast density status be reported to all individuals receiving a mammogram. The new guidelines now require individuals with dense breast tissue be notified of this status. The guidelines also recommend these women discuss additional screening options with their healthcare providers1. These additional screening options may include breast tomosynthesis, breast MRI, breast ultrasound, and/or molecular breast imaging. Many of these options require additional exposure to radiation, are expensive, and are not equitably available across the country. In addition, they all require a follow-up appointment. Compliance can be challenging given the top barriers to mammography cited include the need for transportation, child-care, and the ability to take time off from work2. Genece Health is developing a simpler and less expensive screening solution that identifies the presence of early to late-stage breast cancer using cfDNA from a single blood draw. The Genece Health assay utilizes an algorithm that leverages Artificial Intelligence and Machine Learning to analyze fragment size and end motif patterns in cfDNA as well as regional mutational density to detect presence of ctDNA originating from breast cancer. This algorithm provides highly sensitive and specific results in a preliminary data set. Methods: The preliminary data set, presented herein, is a cohort of over 50 retrospective breast cancer plasma samples and over 100 presumed normal samples. The breast cancer samples were collected at all stages of progression, from stage 0, or ductal carcinoma in situ (DCIS), through stage IV. The majority ( >50%) were from stage I breast cancer. 400 µL of double spun plasma, collected in Streck BCT devices, was processed to purify and isolate cfDNA. cfDNA was used to create WGS libraries that were sequenced on a NovaSeq 6000. Sequence data were analyzed using a bioinformatics pipeline that yields an ensemble probability that correlates to the presence or absence of ctDNA from breast cancer. Results: The Genece Health assay and algorithm performed with a specificity greater than 85%. With this specificity, the assay had a sensitivity greater than 85% in samples from stages II to IV and a slightly lower sensitivity in stage 0 and I samples. Follow-up analyses were conducted to stratify performance based on breast cancer type (e.g. invasive ductal carcinoma vs invasive lobular carcinoma) and HR, PR, and HER2 status (e.g. HER2-negatives vs HER2-positives). Conclusions: The presented preliminary data indicate that the Genece Health technology can be leveraged as a complement to mammography in indications, such as dense breast tissue, where there is an unmet need for an easy and cost-effective way to monitor for breast cancer. The ability to have a blood-based test to complement mammography could reduce the access barriers most cited by females in the United States. Follow-up studies with greater numbers of samples and additional training and optimizations of the algorithm will yield performance improvements that allow the assay to detect all types and stages of breast cancer.

Abstract PO5-20-12: A Case of Bilateral Breast Cancer in a patient on Ocrelizumab

Abstract Background: Ocrelizumab is an anti-CD20 B cell depleting monoclonal antibodies that was FDA approved in 2017 for Relapsing-remitting multiple sclerosis and primary progressive multiple sclerosis based on two large phase III trials (OPERA I and ORATORIO)1. In these trials, patients being treated with Ocrelizumab developed more malignancies compared to placebo. Among these cancers, breast cancer was prominent occurring in about 0.5-0.8% of the patients in the Ocrelizumab group as opposed to 0% in the placebo group. Here we present a case of bilateral breast cancer in a patient with Multiple Sclerosis (MS) treated with Ocrelizumab. Case Presentation A 66-year-old woman with a long-standing history of relapsing-remitting multiple sclerosis (MS) presented to us with concerns of bilateral masses on a screening mammogram. She was diagnosed with MS 30 years prior to presentation and was initially treated with multiple immunomodulators. However, she had progression of disease and was started on Ocrelizumab two years prior to presentation. She was up to date with her screening mammograms which had been unrevealing till now. Family history was significant for breast cancer in her grandmother in her 70s. Her annual mammogram screening showed bilateral irregular masses. A subsequent right breast ultrasound showed three breast masses(1cm, 0.5cm and 0.5cm respectively) and her left breast showed a 0.5 cm mass. Biopsy from the right breast showed invasive ductal and lobular carcinoma(ER+, PR+, HER2-) and that from the left breast showed invasive lobular carcinoma(ER+, PR+, HER2-).She underwent bilateral mastectomies and sentinel lymph node biopsies. The surgical margins and lymph nodes were negative for malignancy hence radiation was not warranted. Genetic testing revealed one pathogenic variant in MSH3 but was negative for BRCA1 and 2. Since her Oncotype dx score was low, adjuvant chemotherapy was not offered. She was started on aromatase inhibitor and her Ocrelizumab was permanently discontinued. Discussion Ocrelizumab is one of the immunomodulator drugs for MS with a probable mechanism being B-cell depletion. The mechanism of how it causes breast cancer is unknown. However, suggested theory is that B cell inhibitors can increase the risk of breast cancer by inhibiting the potentially protective role of the B cells. The B cells are thought to play a role in the tumor micro-environments as antigen presenting cells and activators of natural killer and cytolytic T cells targeted toward lysis of tumors. Also, B cell presence, specifically CD20 B cells, is linked to a better prognosis in breast cancer. One study has also pointed out the importance of timing of anti-b cell therapy in relation to cancer morbidity. Treatment of mice with Anti-CD20 therapy prior to tumor challenge did not result in cancer metastasis. Whereas post tumor challenge, there was increased tumor cell survival and metastasis. Our patient although had a family history of breast cancer, did not have a genetic mutation that could have contributed to her breast cancer. Her breast cancer developed after her therapy with Ocrelizumab hence raising suspicion for causation. With rise in the use of immunosuppressive therapies, further data is needed to delineate pathogenesis. Women with MS have lower all-cause survival after breast cancer diagnosis than women without MS. Hence it is important to identify any risk factors or therapies that might be associated with increased risk of cancer. Citation Format: Kriti Mehra, Mohamad Hejazi. A Case of Bilateral Breast Cancer in a patient on Ocrelizumab [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-20-12.

Abstract PO5-26-07: Surgery for Invasive Lobular Carcinoma: A Patient Experience Survey from the Lobular Breast Cancer Alliance

Abstract The Lobular Breast Cancer Alliance (LBCA) is a nonprofit, patient advocacy organization committed to raising awareness and promoting research into invasive lobular carcinoma (ILC). While ILC accounts for 15% of breast cancers, knowledge about ILC remains limited. ILC’s hallmark is lack of E-cadherin, which results in non-cohesive formation and impacts accuracy of imaging tests and staging. Consequently, patients with ILC have higher rates of positive surgical margins, mastectomies, and axillary lymph node (LN) dissections. To understand the surgery experience of individuals with ILC, LBCA conducted an anonymous online survey from 6/21-7/2/23, distributed via the LBCA newsletter, social media, and partner organizations. Questions addressed pre-operative imaging, type of surgery, surgical margins, LN status, decision making about and patient experience with surgery. Analyses were limited to those respondents who had surgery. Study limitations include potential recall and selection bias. Results 1,482 individuals with a diagnosis of ILC completed the survey and 1,426 had undergone surgery. 76% were from North America, 11% from England, and 4% from Australia. Average age at diagnosis was 56 (range 31-86). At diagnosis, 38% were clinically stage 1; 37% stage 2; 17% stage 3; and 4% de novo metastatic. 75% had a mammogram that indicated dense breasts. Of 1,426 surgery respondents (SR), 95% reported that ILC was identified in only one breast at diagnosis. 80% had a pre-surgical MRI. MRI revealed larger tumors than seen on other imaging for 43% and revealed previously unseen contralateral ILC for 3%. 375 (26%) of SRs were diagnosed with ipsilateral disease and had a pre-surgical MRI that did not reveal new information about their ILC. Of these, post-surgical pathology reports indicated 16% had additional ipsilateral foci, 2% contralateral disease, and 40% had larger tumors than seen on pre-surgical imaging. 614 (43%) of SRs had one or more lumpectomy (L), 560 (39%) of SRs had a double mastectomy (DM), and 451 (32%) of SRs had a single mastectomy (SM). 123 (20%) of SRs who had one or more Ls, had a subsequent SM or DM. For those undergoing L (614), reasons for this choice included: recommendation from their care team (83%), wanted to keep their breast (25%), thought it was better for their overall survival (OS) (14%), and 13% indicated they wanted breasts but did not want reconstruction. Of the 560 women who had a DM, 60% indicated that they thought a DM would improve their OS, 50% were concerned about the risk of local recurrence, 47% doubted that imaging would detect future ILC tumors, and 45% noted concern that ILC is more likely to be bilateral. Of note, only 9% had ILC or ILC and another invasive breast cancer in both breasts at initial diagnosis and 31% who had a pre-surgical MRI changed their initial surgical treatment plan. Post surgery, pathology for DM group revealed larger tumors than seen on imaging (57%), and 6% had tumors found in a second breast that were not seen on imaging. For those 451 who had an SM, reasons for this choice included: 75% said it was what their care team recommended, 35% thought it would improve OS, 20% feared risk for local recurrence, and 15% doubted imaging would detect future ILC. Of 614 respondents who had L, 33% had positive margins at first surgery. Of those, 17% reported multiple Ls and M; and 24% reported clear margins were never achieved. Of the 1011 SM or DMs reported, 10% did not achieve clear margins after these surgeries. Conclusion The survey demonstrates the experience of a large cohort of women with ILC, reporting high rates of uncertainty about accuracy of imaging, high rates of repeat surgery, bilateral mastectomies, and positive margins. Patients are factoring concerns about potential extent of disease and future recurrence in their surgical decision making. These results support the need for improved pre-operative staging and imaging modalities specific to ILC. Citation Format: Laurie Hutcheson, Janice Axelrod, Tracy Cushing, Colleen Fitzwater, Rinath Jeselsohn, Gitte Joergensen, Maria Karsten, Miranda Kimm, Megan Kruse, Theresa Langdon, Julia Levine, Mason Mitchell-Daniels, Rita Mukhtar, Barbara Neilsen, Shani Paluch-Shimon, Therese Pross. Surgery for Invasive Lobular Carcinoma: A Patient Experience Survey from the Lobular Breast Cancer Alliance [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-26-07.

Abstract PO5-08-04: Characteristics of breast cancer in carriers of pathogenic variant in ATM in a large academic health center

Abstract Background: Pathogenic variants (PVs) in ATM are associated with an increased risk of breast, pancreas, and other cancers. The clinical and pathological characteristics of ATM-associated breast cancers have not been well defined. Methods: Patients who underwent multigene panel testing between December 2012 and May 2023 and were identified to harbor ATM PVs were included in the study. We analyzed demographics, germline findings, histopathology, genomic recurrence score, and management of ATM PV carriers with breast cancer. Results: A total of 222 individuals were identified to have PVs in ATM, of whom 184 (83%) were female. The majority were Caucasian (n = 179, 81%) and of those, 22 (12%) had Ashkenazi Jewish ancestry. The median age at genetic testing was 52y, with a range of 20-90y. A total of 111 patients (50%) had a personal cancer diagnosis, the most common of which was breast cancer (n = 70; 63%). The median age at breast cancer diagnosis was 53y, with a range of 25-84y. The most common histopathology was invasive ductal carcinoma (74%), followed by DCIS (21%), and invasive lobular carcinoma (5%). The majority of patients had breast tumors with stage 2 or 3 (78%), grade 2 or 3 (92%), ER and/or PR positive (92%) and HER2 negative (70%). One patient had triple-negative breast cancer. Forty-four percent of breast cancers were less than two centimeters, 23% were lymph node-positive, and 29% had lymphovascular invasion. Thirty-eight percent of patients underwent bilateral mastectomy, 54% received radiation therapy, 40% received adjuvant chemotherapy, 24% received neoadjuvant chemotherapy, and 70% received hormonal therapy. Of the 15 breast cancers with known 21-gene recurrence scores, 47% were intermediate (11-26), 33% were high (>=26) and 20% were low (< =10). Other notable cancers observed were pancreas (n = 9), colorectal (n = 6), prostate (n = 5), uterine (n = 4), melanoma (n = 4), and thyroid (n = 4). Conclusion: Our study outlines the clinical and pathological characteristics of ATM-associated breast cancer in a large academic center. The majority of breast cancers were invasive ductal type, early stage, intermediate or high grade, and hormone receptor-positive with an intermediate or high recurrence score. Despite the early stage, a significant proportion of patients underwent bilateral mastectomy. Further studies are needed to better elucidate the unique characteristics of breast cancer in ATM PV carriers in order to provide tailored management guidelines for this population. Citation Format: Ujjwal Karki, Tara Rangarajan, Dana Zakalik. Characteristics of breast cancer in carriers of pathogenic variant in ATM in a large academic health center [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-08-04.

Abstract PO5-13-12: Personalized circulating tumor DNA testing for recurrence detection and treatment response monitoring in patients with metastatic invasive lobular carcinoma

Abstract Introduction Metastatic invasive lobular carcinoma (mILC) presents unique challenges during treatment response monitoring. A higher frequency of metastases to the bone, gastrointestinal tract, uterus, meninges, ovary, and diffuse serosal involvement is observed in mILC. The challenge with mILC is that they can be difficult to detect clinically and radiographically, and consequently clinical progression can be difficult to determine with conventional imaging modalities like CT Scans, thus precluding many patients with mILC from enrolling into clinical trials. Therefore more accurate biomarkers are needed to better assess response to treatment in real time. In this study, we demonstrate the feasibility of longitudinal ctDNA testing for treatment response monitoring in patients with mILC. Methods In this real-world study, longitudinal plasma samples (n=219) from 60 patients with mILC, treated across 52 independent clinics between 7/22/21 and 6/15/23, were analyzed. A personalized, tumor-informed ctDNA assay (SignateraTM bespoke, mPCR-NGS assay) was used for detection and quantification of ctDNA in plasma samples. Results In this cohort, the median patient age at diagnosis of metastatic disease (baseline) was 62.9 years (range: 32.2-79.7). Of the 60 patients, 41 (68%) had ER+PR+HER2-, 7 (12%) ER+PR-HER2-, 4 (7%) ER+PR+HER2+, 2 (3%) ER+PR-HER2+, 1 (2%) triple negative breast cancer; receptor status was not available for 5 (8%) patients. CDH1 (75%) and PIK3CA (42%) were observed to be the top two genes with somatic, nonsynonymous mutations. Mutations in TP53 and TBX3 were observed in 13% of patients, mutations in AKAP9, IGFN1, RBM26, and RFC3 in 10% of patients, and mutations in ESR1 in 6.7% of patients. At variant level, PIK3CA p.H1047R (22%) and RBM26 p.Q701Tfs*23 (10%) were the top two somatic variants identified. The most common CDH1 variant, p.Q23*, was found in 5% of the cases. Of the 60 patients, 37 (61.7%) were ctDNA-positive at all time points while on treatment (chemotherapy/endocrine therapy/targeted therapy) with the first time point collected at a median of 6.7 months (range: 2.5-2307 months) from baseline. Of these 37, imaging/biopsy results after baseline were available for 32 patients, 86% (27/32) of whom progressed. Thirty-two of 37 persistently ctDNA-positive patients had serial ctDNA measurements available, of which 14 (43%) had significant increase in ctDNA levels (average: 47-fold increase, standard deviation: 98) from first to last time points. At some point during their care ctDNA was detectable in all (n=51) patients with evidence of clinical progression. Of the 60 patients, 14 (23.3%) were ctDNA-negative at all time points tested. None of the 14 persistently ctDNA-negative patients had evidence of disease recurrence or progression at the time of initial testing or throughout ctDNA monitoring. The first ctDNA time point was collected at a median of 33.1 months (range: 0.68-92 months) from baseline for these patients,a median of 3 time points was tested per patient (1-12). Of the remaining 9/60 patients, 3 (33%) had sustained ctDNA clearance for a median of 46 days (range: 0-224 days) in response to treatment, and 2 (22%) were initially ctDNA-negative but turned positive 105 and 156 days later, indicating potential resistance to treatment and molecular progression. Additional 4/9 (44%) had ctDNA levels consistently low levels (average: 0.42 mean tumor molecules/mL) while on treatment for a median of 260 days (range: 217-442) and showed no evidence of progression. Conclusions ctDNA status and dynamics correlate well with clinical status of patients with mILC, as determined by conventional monitoring tools such as imaging and biopsy. Our results indicate that personalized, tumor-informed, longitudinal ctDNA testing may serve as a useful tool for detection of progression and monitoring treatment response in mILC patients. Citation Format: Steffi Oesterreich, Antony Tin, Samuel Rivero-Hinojosa, Janie Fielder, Jenifer Ferguson, Ekaterina Kalashnikova, Angel Rodriguez, Minetta Liu, Adrian Lee. Personalized circulating tumor DNA testing for recurrence detection and treatment response monitoring in patients with metastatic invasive lobular carcinoma [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-13-12.

Abstract PO1-16-10: BRCA mutated Male Breast Cancer, hallmarks of a distinct disease. Data from the Spanish Male Breast Cancer Registry (GEICAM/2016-04)

Abstract Background: Male breast cancer (MBC) accounts for approximately 0.25% of all male cancers and < 1% of all BCs. Its incidence is increasing by 1.1% per year. Most population studies indicate that 10-15% of MBC patients (pts) have a germline BRCA2 mutation (BRCA2 mut). Around 5-10% of BRCA2mut male carriers will develop BC at their lives. Preliminary evidence suggests that BRCA2mut MBC pts tend to have a more aggressive disease. Here we present comparative series of MBC with and without BRCA to gain insight on differences between both groups. Methods: GEICAM/2016-04 (NCT03800355) is a retrospective, observational study which includes data from MBC pts diagnosed between 2000 and 2019 throughout Spain. This analysis includes the 1st unselected 186 pts included in the study, who had BRCA1/2 genes mutational status assessed within clinical practice. BC clinical subtypes are defined: luminal (HR+, HER2-), Triple Negative (TN) (HR-, HER2-), and HER2+ (HR+ or HR-); subtype is unknown in 6% pts. Results: 186 validated pts with BRCA1/2 testing were identified, representing the 24% of pts available in the database at the cut-off date (6-Mar-2023). 36 (19%) pts had germline BRCA1/2 mut (4 pts in BRCA1, 31 pts in BRCA 2 and 1 pt in both BRCA1 and BRCA2), and 150 (81%) pts had BRCA1/2 wild type (wt) or a variant of uncertain significance (VUS)/unknown (UK). Median age at BC diagnosis was 62 (34-87) years, 98% pts were Caucasian, and the median body mass index was 27 (18-46) Kg/m2 (overweight). Prior cancer history was reported in 6% BRCA1/2mut BC pts and 11% BRCA1/2wt or vus/uk, and family history included: 56% BC, 8% ovarian cancer, and 14% prostate cancer (PC). PC as part of prior medical history, cancer family history, and 2nd non-breast primary malignancy, was most frequent in BRCA1/2wt or vus/uk pts, with no statistical differences. At first diagnosis, stages III-IV were higher in BRCA1/2mut pts (28% vs. 17%, p=0.0093). Morphologically, invasive carcinoma of no special type (NST) was the most common pattern (92% in BRCA1/2mut vs. 86% in BRCA1/2wt or vus/uk), and lobular invasive carcinoma was not reported up-to-date. Histological grade 2 was the most frequent (54%), but grade 3 was present in 17/36 BRCA1/2mut pts. 88% pts received adjuvant treatment, 7% (neo-)adjuvant, 2% neoadjuvant and 3% did not receive any systemic therapy. Breast conserving surgery was performed in 4% (5/140) BRCA1/2wt or vus/uk EBC pts, and mastectomy was performed in 55% (n=6/11) de novo metastatic pts. In the advanced setting (n=38), visceral lesions were more frequent in BRCA1/2mut pts. Additionally, 92% BRCA1/2mut pts had ≤ 3 organs involved while one third of BRCA1/2wt or vus/uk pts had ≥ 4 metastatic locations. With a median follow-up of 64 months (mo.), median iDFS and DDFS were higher, but not statistically significant, in BRCA1/2wt or vus/uk pts vs. BRCA1/2mut pts. In advanced setting, median PFS to 1L-3L do not show statistically significant differences between both groups. Regarding OS, no differences were also observed, but the median values were not reached. Further detailed information according to BRCA1/2 mutational status and BC subtypes is included in the table below. Conclusions: In this subset analysis of GEICAM/2016-04, BRCA1/2mut pts had some features of worse prognosis, with a more prevalent de novo metastatic disease. No statistically significant differences were observed in outcomes in both early-stage and advanced setting vs. BRCA1/2wt or vus/uk pts. <graphic> Citation Format: Noelia Martínez-Jáñez, Purificación Martínez, Cristina Hernando, Sabela Recalde, Alfonso Sánchez, David Morales, Marta Santisteban, Isaura Fernández, Sonia Del Barco, Esther Zamora, Vega Iranzo, Tamara Martos, Eduardo Martínez-de Dueñas, Silvia Antolin Novoa, Severina Domínguez, Paula Domínguez, Mª José Echarri, Ana Santaballa Bertrán, Xavier Mira, Andrea Blasco, Susana Bezares, Ander Urriticoechea. BRCA mutated Male Breast Cancer, hallmarks of a distinct disease. Data from the Spanish Male Breast Cancer Registry (GEICAM/2016-04) [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-16-10.

Abstract PO1-07-12: Inverse modeling with surface temperature accurately detects the presence of breast cancer

Abstract Breast cancer affects over 250,000 women in the United States every year. Patient outcomes including overall survival significantly decline with large sized tumors and nodal involvement on initial presentation. The introduction of mammogram screening has been instrumental in the early detection of cancer. However, it has lower sensitivity in dense breast tissue and limited specificity which leads to unnecessary additional invasive testing. Several methods such as magnetic resonance imaging (MRI), computed tomography (CT) and ultrasound imaging are used as adjunctive methods. However, there is still a need for cost-effective techniques without additional radiation exposure for breast cancer screening for use with mammography. We propose an adjunctive screening method using surface temperature measurements and inverse breast modeling for early detection of breath cancer. Methods: We enrolled patients who presented with mammogram detected breast tumors that were confirmed to be cancerous lesions by biopsy. We used prone position steady state infrared imaging of bilateral breasts to measure surface temperatures and multi-view MRI images to create patient specific 3D breast models. The inverse technique applies Levenberg-Marquard algorithms (LMA) and utilizes commercial software for thermal transport modeling. The inverse technique predicts a heat generation map normalized for baseline surface temperatures to localize the presence of an underlying tumor. Results: A total of 25 breast tumors (diameter range from 5 to 27 mm) from 24 patients were included in the analysis with a median patient age of 67 years. One patient had bilateral breast tumors. Mammogram data showed inclusion of mixed breast tissue composition including dense and extremely dense breast tissue. LMA accurately detected the tumor in all 25 patients with maximum absolute errors of 7 mm in location of the tumor in the breast and 1.78 mm in diameter. The accuracy of detection was not affected by tumor histology which included invasive ductal and lobular carcinomas, ductal and lobular carcinoma in-situ and atypical ductal hyperplasia. No heat sensitive tumors were detected in the 23 contralateral breasts which acted as internal negative controls. Conclusion: Infrared temperature profiles and inverse modeling successfully detected malignant breast tumors with no missed tumors or false positive results and could be used as adjunctive screening along with mammography, especially in patients with dense breast tissue. Citation Format: Nithya Sritharan, Carlos Gutierrez, Isaac Perez-Raya, Jose-Luis Gonzalez-Hernandez, Alyssa Owens, Donnette Dabydeen, Lori Medeiros, Satish Kandlikar, Pradyumna Phatak. Inverse modeling with surface temperature accurately detects the presence of breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-07-12.

Abstract PO1-01-12: A retrospective cohort study on the effect of adding adjuvant ovarian function suppression to endocrine therapy in premenopausal women with T1-T2 tumor hormone-positive breast cancer on survival and disease recurrence

Abstract Background: Breast cancer is the most common diagnosed cancer in women and is the leading cause of cancer death. Young women diagnosed with breast cancer are at higher rates of adverse outcomes in terms of survival and recurrence. Hormone sensitive breast cancer is the commonest subtype of breast cancer in this group. To date, the standard adjuvant treatment is endocrine therapy for both pre and post-menopausal women. Recent published studies have recommended adding ovarian function therapy to premenopausal women who are at high risk of recurrence. In this study we evaluated the impact of adding adjuvant ovarian function suppression for premenopausal women with small (T1 and T2) hormone receptor positive node negative breast cancer who did not receive any form of chemotherapy on overall survival and disease-free recurrence. Methods: We performed a retrospective study where we evaluated the electronic medical records of 4431 premenopausal women diagnosed with breast cancer in Asan Medical Center in Seoul, South Korea. All the analyzed patients were operated from the period of January 2006 till December 2019. The inclusion criteria were age of 55 and below, T1 and T2 tumors with N0 disease who received selective estrogen receptor modulators (SERM - Tamoxifen) and didn’t receive neo or adjuvant chemotherapy. We compared patients who received SERM (Tam Only) only to patients who received SERM and ovarian function suppression (Tam + OFS) medications. The primary endpoint was overall survival (OS), and the secondary endpoint was mortality and disease-free survival (DFS). We used chi-square test for categorical variables and t-test for continuous variables. The p-value was set as p< 0.05 as statistically significant. Kaplan Meier curve and log rank test were used to analyze the data for overall survival, disease-free survival and mortality. We performed an additional subgroup analysis adjusted to age, tumor size, Ki67%, progesterone receptor, HER2 status and type of operation. Results: There was equal distribution of cases between tamoxifen only group and tamoxifen + OFS group (2121 versus 2310 respectively). The median age in each group was 45 years of age. Tumor size of ≤0.5cm was the commonest in the tamoxifen only group whereas tamoxifen + OFS group had majority of cases with tumor size of 1 - 2cm. Both groups had a Ki-67% of 10-20%. Histologic grade of 2 and nuclear grade of 2 were most commonly representative in the comparing groups. Invasive ductal carcinoma was the most common histological subtype (93-94%) and invasive lobular carcinoma accounted for 5-6% of cases. Regarding immunohistochemistry results, 91-93% of patients were progesterone receptor positive and 68-73% were HER2 negative. The majority underwent breast conserving surgery compared to mastectomy. We have also looked at the pattern of prescribing OFS treatment in the Tamoxifen + OFS group regarding the length of treatment. Nearly 80% of patients received OFS treatment for a period of 1-2 years whereas only 5.2% received < 1 year and 1.8% >2years. After adjusting to age, tumor size, Ki67%, PR receptor and HER2 status, the result was only significant for higher risk of DFS in the TAM + OFS group in Ki67 < 20%. The OFS+TAM had more DFS and mortality events compared to TAM only group. However, the only significant result was the overall survival favoring tamoxifen only group with a p-value of 0.039 and HR of 1.05-7.99. Conclusion: Adding ovarian function suppression to tamoxifen in premenopausal hormone positive node negative T1-T2 tumors didn’t show any benefit in terms of disease-free interval and overall survival. Further studies are advised to assess the benefit of adding ovarian function suppression to this group of patients Table 1: baseline characteristics of Table 2: Disease Free Survival Subgroup Analysis Citation Format: Sarah Al Safi, Hee Jeong Kim, Seonok Kim, Sae Byul Lee, Jisun Kim, Tae-Kyung Yoo, Il-Yong Chung, Beom Seok Ko, Byung Ho Son. A retrospective cohort study on the effect of adding adjuvant ovarian function suppression to endocrine therapy in premenopausal women with T1-T2 tumor hormone-positive breast cancer on survival and disease recurrence [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-01-12.

Abstract PS16-03: Intratumoral dosing of INT230-6 in Early-Stage Breast Cancer Patients Induces Tumor Cell Necrosis and Immunomodulatory Effects: A Phase II Randomized Window-Of-Opportunity Study – the INVINCIBLE Trial

Abstract Background: Larger tumors pose an increased risk for breast cancer (BC) recurrence post-surgery. In addition, most BC outside of the triple negative subtype are considered immunological quiescent and minimally responsive to immunotherapies. One potential method to combat disease recurrence risk and induce immune activation pre-surgery is through a local therapy that could cause cell death to expose tumor antigens, provide adjuvants for anti-tumor immune priming, and thus potentially increase responsiveness to immunotherapies or rates of pathological complete response in combination with chemotherapy. We have conducted a randomized, Phase 2 presurgical Window-Of-Opportunity trial for intratumoral (IT) INT230-6 comprising vinblastine, cisplatin and a diffusion enhancer (SHAO) in patients with early-stage operable BC, the INVINCIBLE trial (NCT04781725). Previous in vivo and clinical studies demonstrated that INT230-6 induces cancer cell death and halts replication while maturing dendritic cells and recruiting T-cells into the tumor. In this trial, IT injections of INT230-6 were conducted to 1) evaluate the safety of regional cytotoxic use on BC, 2) assess the drug’s ability to cause necrosis, 3) assess immune response within the tumor, microenvironment and systemically prior to surgical resection, and 4) understand the genetic pathways involved in immune activity. Methods: Women awaiting surgery for newly diagnosed early-stage intermediate or high-grade T1-T2 invasive BC were recruited to the trial. The study has two parts. Part I was a randomized (2:1) open label trial comparing 1-3 doses of INT230-6 injected weekly versus no treatment prior to surgery to evaluate safety, feasibility, and optimal drug dosing. Part II was a double-blinded randomized (2:1) trial where patients received one IT dose of INT230-6 vs saline injection IT. Results: We successfully recruited 91 patients with age ranges of 40-77 yrs (mean of 60 yrs) with tumor size ranging from 1.1 - 4.8 cm (mean 2.5 cm; SD 0.9 cm). The most common (>10%) AEs were injection site pain, injection site reaction and nausea/vomiting. Approximately 90% of AEs were grade 1. In the study INT230-6 induced necrosis in 64% of subjects (37 out of 58, range 0 to 100%); whereas saline induced partial necrosis in 25% of patients (5 out of 20, range 0 to 10%). The table below shows the results of necrosis for INT230-6 use in the entire study compared to saline injection for all subjects and those with tumors of size T2. A single injection of INT230-6 caused necrosis in various histologies, including invasive lobular carcinoma. Gene expression analysis showed significant differential gene expression between the baseline biopsy and surgical specimens using INT230-6. Pathway analysis identified genes associated with TCR signaling, B cells and T cell activation that were significantly upregulated in the post INT230-6 treatment samples. There was a relative increase in CD4 and CD8 T cells and B and mast cells. Conclusion: Preliminary evidence shows that a single dose of INT230-6 can cause significant intratumoral necrosis compared to saline especially in tumors >2. cm. INT230-6 stimulates an immune response in breast cancers prior to surgery with minimal adverse effects and good tolerability. Given its immune activation properties, INT230-6 shows promising potential in future breast cancer neoadjuvant studies. Table 1: INVINCIBLE Study Tumor Necrosis Results Intratumoral INT230-6 injection compared to IT saline injection Citation Format: Angel Arnaout, Lewis Bender, Megan Hopkins, Vanessa Lopez Ozuna, Linda Liao, Susan Robertson, Vida Talebian, Kianoosh Keyhanian, Arif Awan, Franco Abbate, Ian Walters, Gregory Pond, John Bartlett, Lazlo Radvanyi, Melanie Spears. Intratumoral dosing of INT230-6 in Early-Stage Breast Cancer Patients Induces Tumor Cell Necrosis and Immunomodulatory Effects: A Phase II Randomized Window-Of-Opportunity Study – the INVINCIBLE Trial [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PS16-03.

Abstract PO5-02-13: Distinct differences in the prognostic implication of tumor size for invasive lobular carcinoma of breast when compared to invasive ductal carcinoma

Abstract Purpose Invasive lobular carcinoma (ILC) is the second common types of breast cancer and its clinicopathological feature and outcomes differ from invasive ductal carcinoma (IDC). However, in terms of survival outcomes, there are conflicting data on the prognostic implication of the ILC when compared to that of IDC. This study aims to evaluate the survival outcomes of patients diagnosed with ILC at single center and compared them with those of IDC. Methods We reviewed the data of the 13,034 IDC patients and 935 ILC patients who were treated between January 2005 and December 2022 at Seoul National University Hospital. We investigated the overall treatment outcomes of two histologic types with a special focus on the tumor size and lymph nodes. Result ILC exhibited distinct characteristics compared to IDC, including a larger tumor size (2.6 ± 1.8 vs. 1.9 ± 1.1 cm, p < 0.001) and a higher hormone receptor positivity (97.4% vs. 79.3%, p < 0.001). Additionally, the presence of lymphovascular emboli was lower in ILC (8.0% vs. 24.6%, p < 0.001). While IDC patients showed slightly better overall survival (OS) than ILC (10-year OS, ILC 89.9% vs. IDC 91.1%, the difference was not statistically significant (p = 0.85). However, distant metastasis-free survival (DMFS) was significantly higher in ILC (10-year DMFS, ILC 93.2% vs. IDC 89.9%, p = 0.001). Age at diagnosis, tumor size, presence of lymphovascular emboli, high expression of Ki-67, and higher pathologic N stage were poor prognostic markers for ILC. Multivariate analysis for DMFS showed that age, high expression of Ki-67 and higher pathologic N stage were poor prognostic markers for ILC. Tumor size was not an independent prognostic factor for DMFS (HR: 0.92, 95% CI: 0.72-1.17, p = 0.491) and for OS (HR: 1.18, 95% CI: 0.99-1.41, p = 0.060) in ILC. Conclusion Our data suggest that the tumor size, which is a well-known prognostic factor in IDC, carries distinctly different prognostic implication in ILC. These observation indicate that adjuvant treatment decisions based on tumor size can be tailored to different histologic subtypes of breast cancer. Citation Format: Ik Beom Shin, Eunhye Kang, Ji-Jung Jung, Hawjeong Lee, Jin Young Byeon, Yunhee Choi, Changjin Lim, Jong-Ho Cheun, Hong-Kyu Kim, Han-Byoel Lee, Wonshik Han, Hyeong-Gon Moon. Distinct differences in the prognostic implication of tumor size for invasive lobular carcinoma of breast when compared to invasive ductal carcinoma [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-02-13.

Abstract PO5-20-10: Treatment with CDK4/6 Inhibitor in a Patient with Metastatic Breast Cancer Causing Myelophthisis

Abstract Background: Symptomatic bone marrow metastasis causing myelophthisis is a rare manifestation of metastatic breast cancer, indicating a poor prognosis due to significant cytopenias. CDK4/6 inhibitors are first-line therapies for metastatic hormone-positive breast cancer but remain an unclear choice in breast cancer patients with significant cytopenias due to associated hematological adverse effects. We present a case of biopsy-proven hormone-positive breast cancer with bone marrow infiltration causing profound pancytopenia. CDK4/6 inhibitors were safely administered despite their cytopenic effects. Case Presentation: A 59-year-old female presented after an abnormal annual mammogram and biopsy showed calcifications stromal fibrosis, cyst formation, and usual ductal hyperplasia in the right upper outer quadrant. One month later, she presented to an outside hospital with gingival bleeding, epistaxis, progressive dyspnea on exertion, and generalized weakness. Labs showed severe anemia with a hemoglobin of 4.8 g/dL (baseline 12.1 g/dL), thrombocytopenia with platelets of 5 K/mm (baseline 215 K/mm), LDH of 879, reticulocyte count of 5%, and negative direct Coombs test. Peripheral smear showed no schistocytes, but showed nucleated RBCs, severely reduced platelets, and occasional giant platelets. The patient was treated for presumed ITP, and the presence of nucleated RBCs prompted bone marrow biopsy which confirmed metastatic invasive lobular carcinoma breast cancer (ER 90-95%, PR 90-95%, HER2 1+). She was discharged on letrozole 2.5 mg daily with close outpatient oncologic follow-up. One week later, she presented to our institution with persistent symptomatic anemia and thrombocytopenia. Inpatient systemic therapy was begun using dose-reduced Palbociclib (75mg) and letrozole with close CBC monitoring while also receiving packed red blood cells (goal >6.5) and platelet transfusions (goal >10). Repeat bone marrow biopsy showed extensive marrow fibrosis, but no significant hematopoietic elements. ADAMTS13 was 134%, ruling out TTP, and she was treated again for presumed ITP with dexamethasone and IVIG, Throughout the 4-week admission, her right breast mass decreased in size and she was discharged after completing 3 weeks of Palbociclib with biweekly outpatient transfusions. During follow-up, the patient’s hemoglobin and platelets slowly started to respond allowing her to become transfusion-independent and allowing dose escalation. Restaging scans 2 months after hospitalization showed an overall improvement of disease burden. The patient continued to do well for almost 18 months, however, later redeveloped visceral crisis and is responding to chemotherapy. Discussion: There is limited data on the management of breast cancer with bone marrow infiltration at presentation. A wide range of survival data in different case reports exists, ranging from 5 to 44 months. However, chemotherapy was used in these studies rather than CDK4/6 inhibitors. By far, cytopenias are the most concerning grade 3 and 4 side effect of Palbociclib. Data from the PALOMA-1 trial suggest that hematologic toxicities, specifically neutropenia, were different from those associated with cytotoxic chemotherapies and are more transient and reversible in nature. Studies have examined the in vitro mechanism of bone marrow suppression in Palbociclib versus cytotoxic chemotherapy, and its cytostatic effect on neutrophil precursors allows for hematological toxicities to be transient. With strong supportive care measures, patients in bone marrow visceral crisis can be safely treated with cytopenic CDK4/6 inhibitors. Citation Format: Nikita Dahake, Jordan Senchak, Jalil Nasibli, Jason Incorvati. Treatment with CDK4/6 Inhibitor in a Patient with Metastatic Breast Cancer Causing Myelophthisis [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-20-10.

Abstract ED02-03: Innovative approaches at the diagnosis and treatment of invasive lobular carcinoma

Abstract Invasive Lobular Carcinoma (ILC) represents a unique subtype of breast cancer characterized by distinctive clinical and molecular features. This presentation aims to delve into innovative approaches in the diagnosis and treatment of ILC, focusing on novel techniques in imaging, unique molecular findings, signaling pathway alterations, targetable biomarkers, and microenvironment profiling that can pave the way for the development of novel therapies. Imaging Techniques in ILC: Accurate diagnosis is the foundation for effective treatment. ILC often presents diagnostic challenges due to the fact that lobular cells tends to infiltrate the affected organs in a diffuse manner instead of forming a discrete tumor mass making diagnostic imaging such as screening mammograms and CT scans less precise. This presentation will explore cutting-edge imaging techniques such as contrast-enhanced mammography, novel radioisotopes for positron emission tomography (PET) such as Fluoroestradiol F18 (FES), Fluciclovine and prostate-specific membrane antigen (PSMA) for improved detection and characterization of ILC lesions. Furthermore, we will discuss emerging modalities like radiomics and artificial intelligence, which hold promise in enhancing early diagnosis and risk assessment. Molecular Insights into ILC: ILC is distinguished by its unique molecular profile, notably the loss of E-cadherin expression. We will delve into recent advancements in understanding the molecular landscape of ILC, including genomic alterations, epigenetic changes, and the role of signaling pathways providing insights into potential therapeutic vulnerabilities. Targetable Biomarkers and Pathways: Identification of targetable biomarkers is essential for the development of precision therapies in ILC. This presentation will highlight promising targets, including ERBB2 (HER2), ROS1, TROP2, AKT1 along with other novel biomarkers. Microenvironment Profiling: The tumor microenvironment plays a pivotal role in cancer progression and therapy response. We will discuss recent advancements in characterizing the ILC microenvironment, including the immune cell infiltrate and stromal components. Understanding the dynamic interplay between the tumor and its microenvironment can inform the development of immunotherapies and combination strategies tailored to ILC. In conclusion, this presentation will provide a comprehensive overview of the latest innovations in ILC diagnosis and treatment. Our exploration of advanced imaging techniques, molecular findings, targetable pathways, biomarkers, and microenvironment profiling will shed light on the exciting potential for personalized therapeutic approaches in the management of ILC. By staying at the forefront of these developments, we can pave the way for improved outcomes and enhanced quality of life for patients with ILC. Citation Format: J. Mouabbi. Innovative approaches at the diagnosis and treatment of invasive lobular carcinoma [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr ED02-03.

Invasive lobular carcinoma of the breast; clinicopathologic profile and response to neoadjuvant chemotherapy over a 15-year period

IntroductionInvasive lobular carcinoma (ILC) accounts for 5–15% of invasive breast cancers. Typical ILC is oestrogen receptor (ER) positive and human epidermal growth factor receptor 2 (HER2) negative. Atypical biomarker profiles (ER- and HER2+, ER+ and HER2+ or triple negative) appear to differ from typical ILCs. This study compared subtypes of ILC in terms of clinical and pathological parameters, and response to neoadjuvant chemotherapy (NACT) according to biomarker profile. MethodsAll patients with ILC treated in a single centre from January 2005 to December 2020 were identified from a prospectively maintained database. Clinicopathologic and outcome data was collected and analysed according to tumour biomarker profile. ResultsA total of 582 patients with ILC were treated. Typical ILC was observed in 89.2% (n = 519) and atypical in 10.8% (n = 63). Atypical ILCs were of a higher grade (35% grade 3 vs 9.6% grade 3, p < 0.001).A larger proportion of atypical ILC received NACT (31.7% vs 6.9% p < 0.001). Atypical ILCs showed a greater response to NACT (mean RCB (Residual Cancer Burden Score) 2.46 vs mean RCB 3.41, p = 0.0365), and higher pathological complete response rates (15% vs 0% p = 0.017). Despite this, overall 5-year disease-free survival (DFS) was higher in patients with typical ILC (91% vs 83%, p = 0.001). ConclusionsAtypical ILCs have distinct characteristics. They are more frequently of a higher grade and demonstrate a superior response to NACT. Despite the latter, atypical ILCs have a worse 5-year DFS which should be taken into consideration in terms of prognostication and may assist patient selection for NACT.

Histological Patterns and Mammographic Presentation of Invasive Lobular Carcinoma Show No Obvious Associations.

Invasive lobular carcinoma of the breast has different mammographic appearances, including spiculated or lobulated masses, architectural distortion, increased breast density, and the possibility of also being occult. Histologically, the morphology is also variable, as several patterns have been described beside the classical one, including the solid, the alveolar, the trabecular, the one with tubular elements, and others. Of 146 ILC cases, 141 were reviewed for mammographic appearance and 136 for histological patterns by two radiologist and two pathologists, respectively; 132 common cases were analyzed for possible associations between mammographic presentation and the histological patterns. Interobserver agreement on the presence or absence of a given mammographic morphology ranged from 45% (increased density) to 95% (occult lesion); the most common radiomorphology was that of a spiculated mass. Interobserver agreement on the presence or absence of a given histological pattern ranged between 79% (solid) and 99% (classical) but was worse when semi-quantification was also included. The mammography-pathology correlation was less than optimal. Multifocality was more commonly detected by histology. The identification of a mammographic mass lesion often coincided with a mass-like lesion on the histological slides and vice versa, but nearly half of the mammographically occult lesions were felt to have masses on histological slides assessed grossly. Histological patterns showed no obvious associations with one or the other mammographic appearance.

Innovation in Breast Cancer Treatment and it's Potential in Pakistan.

Breast cancer is the second most common cancer globally, following lung cancer. It is a major health concern affecting both men and women, although it is more commonly diagnosed in women. Breast cancer is responsible for a significant number of cancer-related deaths worldwide, as it ranks fifth globally. Breast cancer surpasses all other types of cancer in its worldwide impact, and the occurrence of breast cancer is on the rise.1 Breast cancer can be divided into histological subtypes depending on the appearance of the cells under the microscope. The most common types include invasive ductal carcinoma, invasive lobular carcinoma, and ductal carcinoma in situ. A study conducted in 20222 highlighted the novel approach to inhibit PI3K/AKT pathway using a highly potent oral inhibitor Capivasertib. In preclinical trials it has shown promising outcomes by suppressing tumor growth and reducing the phosphorylation of biomarkers such as PRAS40, GSK3b, and S6. Furthermore, phase I/II trials that evaluated the used of capivasertib along with other antineoplastic agents such as paclitaxel, fulvestrant or Olaparib showed enhanced efficacy with manageable side effects as the toxicity profile was within the acceptable range. Another trial also demonstrated clinically significant activity of capivasertib in rare cancers such as AKT1 E17K-mutated tumor.3 Research conducted in Karachi indicates a notable increase in the prevalence of breast cancer across women of various age groups. Furthermore, the study anticipates a continued upward trend in the coming years.4 The study observed not only a rise in the age-specific incidence rate among Pakistani women but also forecasted a sustained elevation in the peak age of onset, particularly in post-menopausal women. A substantial concern for Pakistan is reflected in the fact that breast cancer constitutes 28.7% of newly diagnosed cancer cases in women, highlighting the gravity of this health issue.5 Researchers have made great strides in the treatment of many types of breast cancer, but the battle continues many fronts. However, the success of several biological drugs such as Capivasertib in treatment of people with a specific tumor promises the potential targeted treatments in the most vulnerable of regions such as Pakistan.

Correlation between sentinel lymph node biopsy and non-sentinel lymph node metastasis in patients with cN0 breast carcinoma: comparison of invasive ductal carcinoma and invasive lobular carcinoma

BackgroundSome studies have suggested that axillary lymph node dissection (ALND) can be avoided in women with cN0 breast cancer with 1–2 positive sentinel nodes (SLNs). However, these studies included only a few patients with invasive lobular carcinoma (ILC), so the validity of omitting ALDN in these patients remains controversial. This study compared the frequency of non-sentinel lymph nodes (non-SLNs) metastases in ILC and invasive ductal carcinoma (IDC). Materials Methods: Data relating to a total of 2583 patients with infiltrating breast carcinoma operated at our institution between 2012 and 2023 were retrospectively analyzed: 2242 (86.8%) with IDC and 341 (13.2%) with ILC. We compared the incidence of metastasis to SLNs and non-SLNs between the ILC and IDC cohorts and examined factors that influenced non-SLNs metastasis. Results: SLN biopsies were performed in 315 patients with ILC and 2018 patients with IDC. Metastases to the SLNs were found in 78/315 (24.8%) patients with ILC and in 460 (22.8%) patients with IDC (p = 0.31). The incidence of metastases to non-SLNs was significantly higher (p = 0.02) in ILC (52/78–66.7%) compared to IDC (207/460 − 45%). Multivariate analysis showed that ILC was the most influential predictive factor in predicting the presence of metastasis to non-SLNs. Conclusions: ILC cases have more non-SLNs metastases than IDC cases in SLN-positive patients. The ILC is essential for predicting non-SLN positivity in macro-metastases in the SLN. The option of omitting ALND in patients with ILC with 1–2 positive SLNs still requires further investigation.

Integration of Pathological Criteria and Immunohistochemical Evaluation for Invasive Lobular Carcinoma Diagnosis: Recommendations From the European Lobular Breast Cancer Consortium

Invasive lobular carcinoma (ILC) is the second most frequent type of breast cancer (BC) and its peculiar morphology is mainly driven by inactivation of CDH1, the gene coding for E-cadherin cell adhesion protein. ILC-specific therapeutic and disease-monitoring approaches are gaining momentum in the clinic, increasing the importance of accurate ILC diagnosis. Several essential and desirable morphologic diagnostic criteria are currently defined by the World Health Organization, the routine use of immunohistochemistry (IHC) for E-cadherin is not recommended. Disagreement in the diagnosis of ILC has been repeatedly reported, but interpathologist agreement increases with the use of E-cadherin IHC. In this study, we aimed to harmonize the pathological diagnosis of ILC by comparing 5 commonly used E-cadherin antibody clones (NCH-38, EP700Y, Clone 36, NCL-L-E-cad [Clone 36B5], and ECH-6). We determined their biochemical specificity for the E-cadherin protein and IHC staining performance according to type and location of mutation on the CDH1 gene. Western blot analysis on mouse cell lines with conditional E-cadherin expression revealed a reduced specificity of EP700Y and NCL-L-E-cad for E-cadherin, with cross-reactivity of Clone 36 to P-cadherin. The use of IHC improved interpathologist agreement for ILC, lobular carcinoma in situ, and atypical lobular hyperplasia. The E-cadherin IHC staining pattern was associated with variant allele frequency and likelihood of nonsense-mediated RNA decay but not with the type or position of CDH1 mutations. Based on these results, we recommend the indication for E-cadherin staining, choice of antibodies, and their interpretation to standardize ILC diagnosis in current pathology practice.