Haddad, TC

Abstract Introduction: An Our Practice Advisory (OPA), formerly known as Best Practice Advisory (BPA), is an electronic health record (EHR) tool. OPAs identify key parameters to alert providers of potential interventions that could enhance quality of care. Such functionality is increasingly relevant given the rapid pace of new drug approvals. Within the Mayo Clinic system, we previously identified that amongst Mayo Clinic patients (pts) meeting the MonarchE criteria, 28% of pts did not undergo a documented discussion with their provider regarding the role of adjuvant abemaciclib (Premji, SABCS 2024). Further, a Flatiron study identified that only 40% of eligible pts received abemaciclib (Sandoval, Miami Breast 2025). To address this practice gap, in 2024 we began to implement EHR clinical decision support by creating an OPA trigger for pts eligible for an adjuvant CDK 4/6 inhibitor (CDK 4/6i). Here we report on ‘action taken’ versus not for the OPA and the most common reasons for re-prompts. Methods: The Mayo Breast Disease Group designed an OPA including pts who are within 14 months of a clinical or pathologic diagnosis of high-risk early-stage breast cancer. We leveraged structured data captured in the Epic staging forms (Epic Systems) to identify pts with clinical or pathologic T-stage, N-stage, grade, ± Ki-67/ multigene signature to identify ER+/HER2- pts eligible for adjuvant ribociclib or abemaciclib based on FDA approvals. The OPA was triggered by a patient encounter in oncology when endocrine therapy (but not CDK4/6i) was on the active medication list resulting in a hard stop. The OPA gathered limited details about whether adjuvant CDK4/6 inhibitors were discussed and whether the provider followed a link that resulted in prescribing one—considered an indicator of action taken. In this IRB-exempt quality improvement project, we describe the responses captured in the OPA trigger utilizing Epic tools. Results: The OPA went live on 1/10/2025. Over a 5-month period post OPA initiation, we identified 517 OPA alerts among 332 unique pts. Their median age was 62.5 years, and the majority were female (97%). The median time to resolve the OPA was 17.5 seconds (range 2-567 seconds). 12.6% (65/517) of the time there was ‘action taken’ by selecting the hyperlink to potentially start a treatment plan. Providers selected the following OPA pre-set responses: ‘re-prompt in one month’ 248 (48%), ‘patient not a candidate for therapy’ 48 (9%), ‘patient declines’ 69 (13%), ‘outside oncologist will prescribe’ 36 (7%), ‘not discussed’ 44 (9%), and unknown 72 (14%). The most common free text comments among the 517 OPA alerts (summarized) included: ‘revisit in future’ 108 (21%), ‘too early’ 65 (13%), ‘patient declines’ 66 (13%), ‘outside oncologist will start’ 31 (6%), ‘not a candidate’ 26 (5%), and ‘co-morbidities’ 18 (3%). Erroneous OPA prompting occurred in 14 (3%) who previously failed a CDK4/6i due to toxicity and in 18 (3%) for pts currently on a CDK4/6i. 30 (6%) OPA comments noted that they discussed or started therapy that day. Conclusion: The OPA offered clinical decision support and ensured that clinicians considered prescribing CDK 4/6i in all pts identified as eligible, and captured deferrals. Refinements are needed to ensure appropriate timing of OPA and minimize erroneous firing. The OPA remains active and captures the reason for deferral of adjuvant CDK 4/6i prescription. This data pairs real world decision making to better understand clinically meaningful application of improved invasive disease-free survival (iDFS). Citation Format: S. Premji, P. Advani, S. Chumsri, L. Mina, J. Taraba, J. Carroll, J. Hoppenworth, E. Cathcart-Rake, T. Haddad, B. Rudder, G. Choong, D. Idossa, C. O’Sullivan, S. Yadav, K. Ruddy, P. Peethambaram, T. Hobday, M. Goetz, R. Rao, B. Ernst, F. Batalini, R. Leon-Ferre, A. Tevaarwerk, K. Giridhar. Implementing an Our Practice Advisory (OPA) to provide clinical decision support for adjuvant CDK4/6 inhibitors in early-stage hormone receptor positive breast cancer: The Mayo Clinic Experience [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS5-11-10.

Abstract Intro: The 70-gene MammaPrint (MP) assay is prognostic for distant recurrence and predictive of benefit from adjuvant chemotherapy (CT) benefit established on surgical tissue of systemically untreated patients (pts). The MP index range is from -1 to +1 with higher index indicating lower risk of early recurrence. Risk is categorized as MP High Risk, MP Low Risk, and MP UltraLow Risk, and results can guide treatment decisions. Pts with MP index >0 are classified as Low Risk and derive little benefit from CT. There are clinical scenarios in which the only available tissue for MP or other genomic testing has been exposed to neoadjuvant endocrine therapy (NET). Few studies have investigated the impact of ET exposure on MP index. Methods: Pts were identified through the I-SPY Low Risk Registry (LRR), an observational sub-study which enrolled pts with hormone receptor positive (HR+)/HER2-negative early breast cancer ineligible for the I-SPY2 trial due to MP Low Risk or UltraLow Risk status, between 2010-2020. Pts were treated at the discretion of their provider. We conducted a retrospective analysis of MP index from paired tumor tissue obtained from systemically untreated diagnostic core biopsies and surgical specimens after NET. MP categories and index before and after NET were compared. Change in MP index was assessed for an association with changes in clinicopathologic factors obtained through the LRR using the paired-t test. Results: 28 pts with paired tumor samples were included in the analysis. Median age was 48 (range 31-75) and 18 (64%) were premenopausal. At baseline, 13 (46%) were clinically node-positive and 22 (76%) had ductal histology. Tumor grade was 1 in 6 pts (21%), 2 in 20 pts (71%), and 3 in 2 pts (7%). ER expression was >95% in 25 pts (range 60-100%) and PR expression was >90% in 14 pts (range 0-100%). NET regimens included tamoxifen +/- ovarian function suppression (OFS) in 3 pts (10.7%), aromatase inhibitor (AI) +/- OFS in 15 pts (53.6%), tamoxifen followed by or in combination with AI +/- OFS in 8 pts (28.6%), fulvestrant in 1 pt (3.6%) and OFS alone in 1 pt (3.6%). 11 (61%) of premenopausal pts received OFS. 96% (27/28) of pts were classified as Low Risk both pre- and post-NET. Only one pt had MP change from Low Risk to High Risk. Three pts had change from Low Risk to UltraLow Risk or vice versa. As a continuous variable, a small average increase in MP index was observed after NET; but, there was a range of responses. 19 pts (68%) had an increase in MP index after NET, while 9 pts (32%) had a decrease. In those with a decrease in MP index, the average ER expression decreased by -13.6%, whereas in those with an increase in MP index, ER expression was unchanged (-0.18%) (p=0.049). There was no significant difference in changes in PR expression between tumors with increased vs decreased MP indices. At a median follow-up of 35 months, 4 distant recurrences were observed. Of the 9 pts with a decrease in MP index, 3 pts (33%), including the one who changed from Low Risk to High Risk, experienced a distant recurrence. In contrast, in those with an increase in MP index, 1 of 19 (5%) experienced a distant recurrence. Conclusion: In pts with early-stage HR+/HER2- MP Low Risk or UltraLow Risk breast cancer, NET had minimal impact on the tumor MP classification. These data suggest that the MP assay could be used for tissue exposed to NET if untreated tissue is not available. Further investigation in larger cohorts is needed to validate these findings. The observation that there were more distant recurrences in pts with tumors that had an increase in MP after NET is hypothesis generating, and potentially clinically relevant if validated in a larger study. The potential of MP as a dynamic risk marker to stratify recurrence risk following NET is being evaluated in the ongoing I-SPY2 Endocrine Optimization Pilot. Citation Format: S. Jacob, C. Wu, A. Glas, C. Yau, L. Brown-Swigart, G. Hirst, T. Haddad, K. Giridhar, A. Elias, R. Mukhtar, L. Huppert, K. Albain, D. Yee, L. van’t Veer, L. Esserman, J. Chien. Impact of Neoadjuvant Endocrine Therapy on MammaPrint Index in Hormone Receptor-Positive, HER2-Negative MammaPrint Low Risk Early-Stage Breast Cancer [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS4-05-28.

Abstract Significance: Emergence of resistance to endocrine therapies represents a major challenge in theclinical management of estrogen receptor positive (ER+) breast tumors. CDK4/6 inhibitors(palbociclib, ribociclib, abemaciclib) have improved survival when combined with endocrine therapy. Nonetheless, resistance to CDK4/6 inhibitors eventually occurs. One of the emerging mechanisms ofresistance toward endocrine therapy and CDK4/6 inhibitors is characterized by the enrichment ofbreast cancer stem cells (CSCs) that show stem-like features such as self-renewal capacity, highCD44 expression and ALDH activity. We have demonstrated that Aurora-A kinase (AURKA) has apivotal role in promoting cancer cellular plasticity and clonal expansion of endocrine resistantCD44high/ALDHhigh CSCs. Our preclinical studies on AURKA-driven tumor stemness provided thetherapeutic foundation for a Phase-II clinical trial (TBCRC041) of the AURKA inhibitor, alisertib, whichdemonstrated clinically meaningful activity in patients with endocrine and CDK4/6 inhibitors resistantER+ metastatic breast cancer (MBC). Despite such activity, alisertib resistance finally occurred. Therefore, we hypothesize that up-regulation of IL6R/STAT3 and PR stemness oncogenic pathwaysmay sustain the clonal expansion of CD44high/ALDHhigh CSCs after tumor progression on AURKAinhibitors. Experimental Design: We used variant MCF-7 breast cancer models that show resistance toendocrine therapy (letrozole and fulvestrant) and alisertib (MCF-7 LR/FR, MCF-7 LR/FR-AlisR) todefine in vitro and in vivo the efficacy of stemness-targeted therapies to enhance alisertib activity byimpairing the enrichment of hormone refractory CD44High/ALDHHigh CSCs. Parental MCF-7 cells wereused as control. We employed exclusive PDX-derived 3D-Mammospheres (MPS) that wereestablished from the Phase-II clinical trial TBCRC041 to test the efficacy of stemness-targetedtherapies in enhancing the therapeutic activity of alisertib. In Vitro Studies: Immunofluorescence andimmunoblot assays were used to assess the expression of breast cancer stemness biomarkers. Enrichment of ALDHHigh CSCs was measured using Red-Aldefluor kit. Cell proliferation and Red-Annexin-VHigh apoptotic cells were quantified in real-time using IncuCyte S3. In Vivo Studies: 1x106breast cancer cells were injected into the mammary fat pad of NSG-female mice and treated withfulvestrant, alisertib and tocilizumab as monotherapy or in combination. Control groups were treatedwith saline solution placebo. Drug Treatments: Tocilizumab and Onapristone were used to inhibit theIL6R/STAT3 and PR stemness pathways, respectively. Results: Our study demonstrates for the first time that nuclear STAT3/PR complex mediatesAURKA-induced expression of KLF4 stemness gene and enrichment of endocrine resistantCD44high/ALDHhigh CSCs. Alisertib resistant MCF-7 LR/FR cells showed increased expression ofIL6R, T288-AURKA, S727-STAT3 and S294-PR compared to alisertib naïve cells. MCF-7 LR/FR-AlisR-derived 3D-MPS had increased KLF4 and CD44 expression. Alisertib resistant PDX modelsalso showed high levels of CD44, IL6R/STAT3 and KLF4 expression. Remarkable, pharmacologicalblockade of PR and STAT3 transcriptional regulatory networks enhanced the efficacy of alisertib byreducing the enrichment of CD44High/ALDHHigh CSCs. Conclusions: These findings provide the strong preclinical rationale for the development of novelcombinatorial therapeutic strategies targeting IL6R/STAT3 and PR stemness pathways to enhancethe efficacy of AURKA inhibitors that will result in the selective eradication of CD44High/ALDHHighCSCs with consequent benefits on the overall survival of patients with advanced ER+ breast tumorsrefractory to endocrine therapies and CDK4/6 inhibitors.輀 Citation Format: A. B. D'ASSORO, M. Drago, T. Haddad, M. GOETZ, K. Giridhar, K. Kalari, L. Manzella, P. Vigneri, F. Drago, C. Vancheri, C. Lange, J. Ingle. Stemness-targeted therapies to enhance the efficacy of AURKA inhibitors in endocrine resistant er+ breast cancer [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS2-11-08.

Abstract Introduction Serial assessments of circulating tumor cells (CTCs) in metastatic breast cancer (MBC) provide independent prognostic significance for progression free survival and overall survival. A low CTC burden (<5 CTCs / 7.5mL blood) at baseline is favorable prognostically, and reduction of CTCs during treatment indicates response to treatment (Janni, CCR 2025). Despite increasing evidence supporting its clinical validity, real-time serial CTC enumeration has not been utilized broadly in clinical practice in the U.S. The ACT-MBC study is a prospective observational study to evaluate the impact of serial CTC testing on treatment decisions and response assessment (NCT05662345). Provider (physician or advanced practitioner) perception of CTC testing is measured with questionnaires at baseline (PQ1), and for each pt during the first restaging visit (PQ2), and at the end of the study (PQ3). We previously reported PQ1 results (Giridhar, SABCS 2024). Here, we report on results of PQ2. Methods ACT-MBC prospectively enrolled patients (pts) at Mayo Clinic Rochester and Mayo Clinic Health Systems sites (Mankato, Albert Lea and Eau Claire). Pts with MBC were enrolled at time of progressive disease during any line of therapy (TNBC) or ≥2nd line metastatic therapy for ER+/HER2- disease. Pts were tested for CTCs using the FDA-cleared CellSearch® assay which included enumeration and biomarker testing on CTCs for ER, HER2, and PD-L1. The treating clinician determined the regimen and timing of restaging scans. CTC testing was performed once per cycle (every 3-4 weeks) with results returned to the treating provider within 7 days. We descriptively summarized PQ2 responses from providers who had at least one on-treatment CTC result available by the first restaging visit. We report the proportion (90% CI) of providers who agreed or strongly agreed that assessing CTCs enhanced their ability to determine response to therapy and that the CTC results helped guide their decision to continue or change therapy (co-primary endpoints) while accounting for within provider correlation. Results As of June 25, 2025, 15 providers enrolled a median of 2 pts each (range: 1 to 15 pts) and completed PQ2 surveys on 40 pts. 7 providers (47%) practiced in the community setting and 4 (27%) were nurse practitioners. Most pts were female (98%), White (98%), and had ER+/HER2- MBC (80%). Baseline (C1) CTC results were elevated (≥5 CTCs) in 24 (60%) pts (CTC range 0-609). At C2 (n=39), CTC values remained undetected in 7 pts, decreased in 21 pts, increased in 8 pts, and remained unchanged in 3 pts. At PQ2 (n=40), based on clinician interpretation of radiographic findings, results showed 2.5% of pts with complete response, 20% with partial response, 25% with stable disease, 17.5% with mixed response, and 35% with progressive disease. Clinicians reported that CTC results were concordant with imaging results in 34 (85%) responses, discordant with imaging in 7.5% of responses, and unclear in the remaining 7.5% of responses. Most clinicians (82.5%) agreed or strongly agreed that assessing CTCs enhanced their ability to determine response to therapy (90% CI: 68.3%, 96.7%). Further, 70% of providers agreed or strongly agreed that the CTC results helped guide their decision to continue or change therapy (90% CI: 50.8%, 89.2%). 32.5% of the time, CTCs results influenced the timing of the first restaging scans. In 11/25 pts without progressing disease, CTC results influenced the timing of future scans. In the 7/8 pts with a mixed response at first restaging scans with decreasing CTCs, 4 remained on the same systemic therapy. Conclusions Oncologists in academic and community practice responded that serial CTC assessments enhance ability to determine response of therapy, guide decisions to continue or change treatments, and influence timing of radiographic assessments. Citation Format: K. V. Giridhar, D. Zahrieh, M. Hanna, A. Singh, E. Al-Hattab, P. Schumacher, J. Carroll, J. Hoppenworth, T. Haddad, A. Tevaarwerk, B. Rudder, G. M. Choong, S. Basu, R. A. Leon-Ferre, T. O'Brien, A. Lewis, F. de Snoo, L. Stork-Sloots, F. K. Kuhr, S. Lazaro, R. Prendergast, D. S. Spinner, M. P. Goetz. Assessing the impact of real-time serial circulating tumor cell results on the management of patients with metastatic breast cancer [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS4-03-10.

Abstract Cyclin dependent kinase 4 and 6 inhibitors (CDK4/6i) are standard first line (1L) and second line (2L) treatments of ER+ MBC. However, the optimal treatment strategy after progression on a CDK 4/6i is unknown. Given concern for rapid disease progression after discontinuation of CDK4/6is (Bashour, J Cancer 2017), further data on responses to subsequent lines of therapy post CDK4/6i are needed. We performed a single institution retrospective review of patients (pts) with ER+ MBC who received 1L or 2L CDK4/6i to examine the prescribing patterns and clinical responses to post-CDK4/6i treatment. Methods: We identified 136 ER+ MBC pts prescribed a CDK4/6i at Mayo Clinic Rochester (from 12/2014 to 2/2018) on 1L or 2L who received at least 30 days of therapy and ≥ two clinic visits during treatment. For the 1L and 2L cohorts we assessed the time to treatment failure during (TTF-1) and after CDK4/6i therapy (TTF-2). TTF was defined as time from start of therapy to discontinuation for any cause. Additionally, we assessed overall survival (OS) post CDK4/6i discontinuation (defined as the date of TTF-1 to death or last follow up). Results: The study cohort included 81 and 55 pts treated with 1L and 2L CDK4/6is, respectively. In the 1L cohort, palbociclib/letrozole (82.3%) and palbociclib/fulvestrant (13.6%) were most commonly prescribed. Treatment was discontinued in 39/81 pts due to: progression (84.6%), intolerability (7.7%), and other (7.7%). The median TTF-1 was 19.7 mo (95% CI 11.2 – 25.4 mo). Subsequent treatment and response data were available in 37/39 pts that progressed on 1L CDK4/6i. The most commonly prescribed regimens included single-agent hormonal therapy (29.7%), everolimus/exemestane (27.0%), and single agent chemotherapy (21.7%). The overall median TTF-2 were as follows: everolimus/exemestane 13.2 mo [95%CI 0.33 mo – not reached (NR)]; single agent hormonal therapy 3.1 mo (95%CI 1.4 – 5.4 mo); and single agent chemotherapy 4.1 mo (95%CI 1.4 - 5.4 mo). With a median post-CDK4/6i follow up of 11.2 mo, we observed 8 deaths and the median OS-post CDK4/6i was NR. In the 2L cohort, common regimens were palbociclib/letrozole (63.6%) and palbociclib/fulvestrant (27.3%). Treatment was discontinued in 30/55 pts due to: progression (73.3%), intolerability (13.3%), and other (13.3%). The median TTF-1 in the 2L cohort was 8.3 mo (95%CI 4.6 – 12.7 mo). Subsequent treatment data were available in 24/30 pts and included single-agent hormonal therapy [n=7 (29.2%); median TTF-2 4.7 mo; 95%CI 1.9 – 14.0 mo], everolimus/exemestane [n=6 (25.0%); median TTF-2 3.2 mo, 95% CI 0.8-10.1 mo)] and single agent chemotherapy [n=6 (25.0%); median TTF-2 2.6 mo; 95%CI 1.7 mo – NR)]. With a median post-CDK4/6i follow up 18.7 mo in the 2L cohort, we observed 11 deaths, and the median OS-post CDK4/6i was 11.8 mo (95%CI 11.8 mo – NR). Conclusions: Single and combination-based endocrine strategies are commonly administered post-CDK4/6i without clinical evidence for rapid deterioration. The observation of a median treatment duration lasting >12 months in patients receiving everolimus/exemestane post-CDK4/6i supports ongoing studies evaluating drugs that target PI3K/mTOR pathway in combination and following progression on a CDK4/6i. Citation Format: Giridhar KV, Choong GM, Leon-Ferre RA, O'Sullivan CC, Ruddy KJ, Haddad TC, Hobday TJ, Peethambaram PP, Moynihan TJ, Loprinzi CL, Liu MC, Suman VJ, Goetz MP. Clinical management of metastatic breast cancer (MBC) after CDK 4/6 inhibitors: A retrospective single-institution study [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-18-09.

Abstract Background: Invasive lobular carcinoma (ILC) of the breast has distinct histological and molecular variations compared to invasive ductal carcinoma (IDC), including absence of the adhesion protein E-cadherin. Recently, molecular subtypes within ILC have been described, with an analysis from The Cancer Genome Atlas (Ciriello et al) identifying three distinct groups within ILC based on gene expression—reactive-like, immune-related, and proliferative. In this study, we applied this 60-gene classifier to a locally advanced cohort of ILC and mixed ILC/IDC cases from patients screening for the I-SPY 2 neoadjuvant chemotherapy trial. Methods: The I-SPY 2 TRIAL is open to women with more locally advanced, clinically/molecularly (as assessed by MammaPrint) high risk breast cancer. HR+HER2- MammaPrint Low risk patients ineligible for I-SPY 2 randomization are invited to join a MP Low risk registry. 131 ILC and mixed ILC/IDC tumors from these cohorts (I-SPY 2: n=80; low risk registry: n=51) with pre-treatment Agilent microarrays were available for analysis. We used the Classification to Nearest Centroid technique to assign TCGA subtype to our cohort. We assessed association between TCGA subtype, clinical covariates and response to therapy using a chi-square test. We also evaluated the Euclidean distance between each sample and the three subtype centroids. In an exploratory analysis, we used consensus clustering based on the 1000 most varying genes within the HR+HER2- I-SPY ILC cases to generate new unsupervised groupings, and assessed the concordance with the TCGA reactive-like, immune-related and proliferative subtype assignments. Results: Of the 131 patients included, most (79%) were HR+HER2-, 11% were HR+HER2+, 2% were HR-HER2+ and 8% were HR-HER2- for a total of 10% HR-. 66 were pure ILC, while 65 were mixed ILC/IDC. Upon applying the TCGA 60-gene classifier, the distribution of ILC subtypes was as follows: 33 (25%) were classified as reactive-like, 50 (38%) were immune-related, and 48 (37%) were proliferative. 64% of triple negative cases were reactive-like; while the HR+HER2- and HER2+ cases were more likely to be in the proliferative or immune-related subtype (p=0.037). Among the 80 I-SPY 2 cases, the overall pathologic complete response rate was low (16%) but equivalent to the overall HR+HER2- I-SPY2 population (16%). This did not differ across the groups defined by the TCGA ILC subtypes (p=0.79). Interestingly, a subset of cases assigned as reactive-like and immune-related were of similar distance to the proliferative subtype centroid as patients assigned to the proliferative subtype. When we used consensus clustering to identify new subsets within our locally advanced ILC cohort, our unsupervised groupings had only 32% concordance with the TCGA ILC subtype assignments. Conclusion: The low concordance between our consensus cluster groupings and the TCGA subtype groupings may reflect underlying differences within a locally advanced cohort of ILC cases, like I-SPY, that may not be captured in the 60-gene classifier developed from the overall lower stage TCGA cohort. These findings suggest that considerable molecular heterogeneity exists in lobular cancers, which merits further investigation. Citation Format: Zhu Z, Yau C, Chien AJ, Haddad T, Esserman LJ, van't Veer L, Mukhtar RA, I-SPY2 Consortium. Molecular subtypes of invasive lobular breast cancer in the I-SPY2 TRIAL [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr PD7-06.

Abstract Background: Combining cyclin dependent 4/6 kinase inhibitors (CDK4/6i) with endocrine therapy (ET) has resulted in clinically significant improvements in progression-free survival (PFS) in persons with hormone-receptor (HR)-positive metastatic breast cancer (MBC). However, nearly all patients will progress on CDK4/6i and ET and the mechanisms associated with primary and secondary resistance are mostly unknown. The identification of biomarkers associated with response to CDK4/6i is therefore a major research priority. PROMISE is a multicenter prospective cohort study designed to perform a comprehensive “omic” assessment of blood, tumor, urine and the fecal microbiome to identify alterations in molecular or cellular features associated with primary endocrine resistance (e.g. disease progression ≤ 12 months on treatment) and acquired resistance to CDK4/6i. Additionally, patient derived xenografts (PDX) and organoids are generated to test new drug strategies designed to reverse resistance to CDK4/6i and ET. Methods: Eligible participants include women for whom palbociclib is recommended in combination with either letrozole (first-line) or fulvestrant (second-line) therapy for HR-positive MBC. As of July 2018, 14 patients have been enrolled; the target accrual is 250 patients, who will be followed over the course of 36 months and followed for at least 12 months after the close of enrollment. Blood and tumor biopsies are obtained at baseline, at the end of cycle 2, and at progression. Whole exome sequencing (germline and tumor) and RNAseq (whole transcriptome) are performed on tumor samples in a CAP/CLIA lab (TEMPUS) and results will be provided back to all patients for later use. Additionally, PDX and organoids are generated from tumor biopsies at baseline and during progression. Blood, stool, and urine samples are collected for additional correlative studies. The primary objective of this trial is to identify novel genomic variants and pathways associated with early progression (≤ 12 months) among women with advanced HR-positive breast cancer treated with palbociclib and ET. Secondary objectives include identification of the biomolecular features within the gut (stool) microbiome and exploration of the metabolomics and proteomics of ER-positive MBC. Results from the interrogation of these biospecimens will be critical to gain insights into treatment resistance. Funding is provided by Mayo Clinic Center for Individualized Medicine, TEMPUS, and an ASCO Career Development Award (COS). ClinicalTrials.gov Identifier: NCT03281902. Citation Format: O'Sullivan CC, Suman VJ, Kalari KR, Moyer A, Sung J, Moreno-Aspitia A, Northfelt DW, Liu MC, Haddad TC, Chumsri S, Couch FJ, Weinshilboum RM, Wang L, Goetz MP. Genetic analysis in blood, urine, stool and tumor samples from patients with advanced or metastatic estrogen receptor positive and HER2 negative breast cancer receiving palbociclib and endocrine therapy (PROMISE) [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr OT3-02-08.

Abstract Background: Stage III triple negative(TN) inflammatory breast cancer(IBC) is associated with a poor prognosis evidenced by a 15 month(mo) median disease free survival(DFS) and overall survival(OS) of 34 mo. The substantial incidence of developing distant metastasis may be due to the prevalence of cancer cells with stem cell-like features (e.g. CD44+/CD24-) in TNIBC. The transcriptional pathway JAK2/STAT3 is associated with the survival of CD44+/CD24- cells, and preclinical data demonstrates overexpression of activated STAT3(pSTAT3) in > 95% of TNIBC. Preclinical studies have shown that ruxolitinib (Incyte®Corporation), an approved JAK1/JAK2 inhibitor, suppresses pSTAT3 in IBC patient derived xenograft models, and when combined with paclitaxel, results in a synergistic reduction in tumor weight. Given the lack of a known therapeutic target in TNIBC, this preoperative proof of principle study exploits the survival mechanism of CD44+/CD24- stem cells prevalent in this disease, by combining ruxolitinib(Rux) with paclitaxel(T) followed by doxorubicin/cyclophosphamide(AC). Methods: Up to 64 pts with newly diagnosed stage III TNIBC (cT4d, any N, M0) are eligible if they have adequate organ function and are willing to undergo 2 research biopsies(rbx) of the affected breast. Following baseline rbx, pts are randomized to a 7 day(d) run-in phase of Rux vs Rux(15 mg bid) + T(80mg/m2/wkx1). A 2nd rbx is obtained after the run-in phase. Pts randomized to RuxT continue to receive a total of Tx12 wks+Rux. Pts randomized to Rux alone, are re-randomized to receive Tx12 wks+Rux vs Tx12wks alone. Following T, all pts receive AC (A-60mg/m2,C-600mg/m2) every 14d x 4. Pts proceed to modified radical mastectomy (MRM) followed by chest wall/regional lymph nodes radiation therapy. Correlatives: To assess the effect of JAK inhibition with Rux on pSTAT3 and STAT3 related gene expression, molecular and genomic markers (e.g. RNA-seq, ChIPseq, FISH) will be determined in each rbx and residual tumor at MRM. The relative frequency and topology of CD44+/CD24- cell population and pSTAT3 expression by IHC will also be assessed in these tumor specimens. IL-6 and CRP plasma concentrations will be measured at baseline, prior to T and AC and prior to MRM. Statistics: The primary endpoint is change in markers of JAK/STAT inhibition. If the proportion of rbx exhibit a biologic response to Rux alone (i.e. change from pSTAT3 expression to pSTAT3 negative) is <10%, then Rux alone is minimally effective on JAK inhibition vs alternative hypothesis that Rux inhibits JAK if the proportion of biologic response is ≥33%. If ≥5/25 rbx treated with Rux alone have a biologic response then the hypothesis that biologic response is ≤10% is rejected with an error rate of 0.098 (target 0.10). If ≤4/25 rbx have a biologic response then the hypothesis that biologic response is ≥33% is rejected with an error rate of 0.05 (target 0.10). Biologic response of rbx with Rux alone will also be compared with the proportion of biologic response to RuxT (33% vs. 66% based upon presumed synergy with RuxT). Secondary endpoints are clinical: pathologic complete response in breast/lymph nodes, Residual Cancer Burden, DFS and OS. Clinical Trial Information: NCT02876302. Citation Format: Overmoyer B, Regan M, Polyak K, Brock J, Van Poznak C, King T, Haddad T, Stearns V, Hwang S, Winer E. TBCRC 039: Phase II study of combination ruxolitinib (INCB018424) with preoperative chemotherapy for triple negative inflammatory breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr OT3-05-01.

Abstract Background: AI's are more effective than TAM in ER+ breast cancer. In AI refractory MBC, the response rate to TAM is 0% (Osborne 2011). Z-Endx is an active metabolite of TAM and among TAM treated women in the adjuvant and metastatic settings, reduced CYP2D6 metabolism and low Endx concentrations (Css <20 nM) have been associated with increased likelihood of disease recurrence. Preclinical studies have demonstrated greater Z-Endx exposure and anti-tumor activity with oral Z-Endx compared to equivalent doses of oral TAM (Reid 2014) Methods: We conducted a phase I trial to determine the maximum-tolerated dose (MTD) and evaluate the toxicities, clinical activity, and pharmacokinetics (PK) of Z-Endx in patients (pts) with ER+, AI refractory MBC. Unlimited prior endocrine regimens were allowed. An accelerated titration schedule was applied (2 pts/dose level) until moderate toxicity or DLT, followed by a 3+3 design and then to expansion cohorts (40, 80, and 100 mg/day). Z-Endx was administered orally once daily (28 day cycle). Eye exams were performed at baseline, and end of cycles 2 and 6. PK was performed during cycle 1 and prior to subsequent cycles. For pts in the expansion cohorts, tumor biopsies were obtained at baseline for DNA sequencing (Foundation Medicine). Plasma cholesterol levels were obtained at baseline and after 1 cycle. Results: From March 2011 to Dec 2014, 41 pts (38 evaluable), median age 60, received Z-Endx once daily encompassing 7 dose levels (20-160 mg/daily). The median number of prior hormonal regimens was 2 and 3 for the dose escalation and expansion cohorts, respectively. Dose escalation was stopped at 160 mg/day given MTD not reached and attainment of mean Endx Css of 3.6 uM. Cycle 1 DLT (PE) was observed in one patient (60 mg). No eye toxicity was observed. PK demonstrated mean Endx Css of > 1 uM at all dose levels ≥ 40 mg/day. Antitumor activity was observed at multiple dose levels including 3 confirmed partial responses and an additional 7 with stable disease for ≥6 cycles. Of these 10 pts, 9 had prior progression on both AI and fulvestrant and 3 additionally on TAM. After 1 cycle, total and LDL cholesterol decreased > 20 points in 54% and 40% of pts, respectively. Tumor sequencing in the expansion cohorts (n=14) did not identify ESR1 mutations; however, ESR1 amplification was identified in 1 pt with prolonged stable disease (>200 days). Of 6 pts with rapid progression (≤2 cycles), 4/6 had either CCND1 amplification (n=1) or at least one of the following activating mutations: ERBB2 L755S (n=1), AKT1 E17K (n=1), MTOR E1799K (n=1). Conclusions: The direct administration of Z-END provides substantial drug exposure, acceptable toxicity, and "proof of principle" antitumor activity in endocrine resistant MBC. While the MTD was not determined, the goal of achieving Endx Css concentrations of > 1 uM was achieved. Tumor sequencing identified pts with predicted and confirmed endocrine resistance. A randomized phase II comparing endoxifen (80 mg/day) with TAM in AI refractory MBC was recently activated (NCT02311933). Supported in part by CA 133049, CA186686, CA15083, CA116201, and CA15083. Citation Format: Goetz MP, Suman VJ, Reid JM, Northfelt DW, Mahr MA, Dockter T, Kuffel M, Buhrow SA, Safgren SL, McGovern RM, Collins JM, Streicher H, Hawse JR, Haddad TC, Erlichman C, Ames MM, Ingle JN. Final results of a first-in-human phase I study of the tamoxifen (TAM) metabolite, Z-Endoxifen hydrochloride (Z-Endx) in women with aromatase inhibitor (AI) refractory metastatic breast cancer (MBC) (NCT01327781). [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr PD2-03.

Abstract Background: During tumor progression, activation of Aurora A kinase (AURKA) is associated with epithelial to mesenchymal transition (EMT) reprogramming and expansion of a subpopulation of tumor initiating cells harboring a CD44+/CD24low/- phenotype [D'Assoro, Oncogene 2014]. These cells are characterized by their capacity to self-renew, resist drug therapies, and promote distant metastases. In ER+ breast cancer (BC) models, activation of AURKA is associated with down-regulation of ERα expression and resistance to endocrine therapy. Alisertib, a selective inhibitor of AURKA, can reverse EMT and restore tumor ERα expression and sensitivity to endocrine therapy [Opyrchal, PLoS One 2014]. As a single agent in HR+ advanced BC, alisertib was associated with a 6-month clinical benefit rate of 54% and median PFS of 7.9 months [Melichar, Lancet Oncol 2015]. The objectives of this phase I trial were to determine the maximum-tolerated dose (MTD) and evaluate the toxicities and clinical activity of alisertib with fulvestrant in patients (pts) with HR+ advanced BC. Methods: In this standard 3+3 dose-escalation phase I study, pts were assigned to two different oral doses of alisertib (40-50 mg BID on days 1-3, 8-10, 15-17 q 28-day cycle) in combination with standard dose fulvestrant (500 mg IM on day 1 and 15 of cycle 1 and then day 1 q 28-day cycle thereafter). Eligibility included HR+ advanced BC, postmenopausal status, measurable disease or nonmeasurable bone disease by RECIST v1.1, ECOG performance status ≤ 1, unlimited prior endocrine therapies, and ≤ 2 chemotherapy regimens in the metastatic setting. Results: Ten pts enrolled September 2014 - April 2015, and 9 were evaluable for the primary endpoint (one excluded due to ineligibility). The median pt age was 59 (range 48, 73). Prior endocrine therapies included AI (9, 100%), fulvestrant (6, 67%), and everolimus/exemestane (5, 56%). Eight pts (89%) had prior chemotherapy. A median of 4 cycles of therapy have been administered (range 1+, 9+). There were no severe (grade 3+) toxicities reported during cycle 1 at either dose level, thus the MTD was not reached. The cycle 1 grade 1/2 adverse events regardless of attribution were fatigue (6, 67%), neutropenia (5, 56%), anemia (5, 56%), leukopenia (4, 44%), diarrhea (3, 33%), nausea (3, 33%), and mucositis (1, 11%). As of June 3, 2015, 2 pts have discontinued treatment due to disease progression, and 7 remain on treatment with stable disease (Table). One pt with bone only disease had a near CR on PET scan. Dose LevelAlisertib Dose (BID)Treatment Cycles≥ Grade 3 Toxicity, All CyclesProgression-Free Survival (days)1 (n=3)40 mg4, 7+, 9+ 117, 170+, 223+2 (n=6)50 mg1+, 2, 3+, 3+, 4+, 5+grade 4 neutropenia (1 pt)28+, 56, 56+, 57+, 112+, 116++ indicates patients still receiving treatment Conclusion: Alisertib in combination with fulvestrant was well-tolerated. The recommended phase II dose is 50 mg twice daily on days 1-3, 8-10, and 15-17 q 28-day cycle with standard dose fulvestrant. Promising antitumor activity was observed. Correlative tissue evaluation of AURKA expression and other EMT biomarkers is underway. Funding: This work was funded by Takeda Oncology and supported by NIH Grant K12 CA90628 [TCH]. Citation Format: Haddad TC, D'Assoro AB, Suman VJ, Opyrchal M, Goetz MP, Ingle JN. A phase I trial to evaluate the safety of the addition of alisertib to fulvestrant in hormone receptor positive (HR+), advanced breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P6-13-04.