Jacob, Saya

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 Introduction: Metaplastic breast cancer (MpBC) is a rare, aggressive subtype of breast cancer that has limited evidence-based data to guide treatment. Historically, MpBC has had limited response to chemotherapy; however, the response of MpBC to antibody-drug conjugates (ADCs) remains poorly characterized. Methods: We performed a retrospective cohort study of patients (pts) with pathologic diagnosis of MpBC who received ADC therapy as part of standard of care in the metastatic setting across 4 NCI-designated cancer centers. The primary endpoints were objective response rate (ORR) at time of best response to ADC & real world PFS (rwPFS) of ADC compared to non-ADC therapy, defined as time from treatment start to time of progression or death. Results: We identified 48 pts with MpBC who received at least one ADC between 3/2016 and 10/2025. Median age was 54 years (range 31-77); all pts were biological females. Most pts had triple negative disease (n=39, 81%), 5 (10%) had HER2+ disease, 3 (6%) had hormone receptor positive disease & 17 (35%) were confirmed HER2-low (IHC 1+ or 2+, ISH nonamplified). The most common MpBC subtypes were with squamous differentiation (n=17, 35%), chondroid (n=11, 23%), matrix-producing (n=11, 23%) & spindle cell differentiation (n=10, 21%). Ten pts (21%) had de novo metastatic disease & 38 (79%) had recurrent disease. Most common metastatic sites were lung (n=33, 69%) & liver (21, 44%). 37/38 (97%) patients had curative intent anthracycline & taxane, with median disease-free interval of 16 months (range 2-241). 18 pts (38%) received curative intent immune checkpoint inhibitor. Most pts received ADC in the first (n=19, 40%) or second line (n=18, 38%) with Sacituzumab govitecan being the most common (n=38, 79%) ADC, followed by Trastuzumab deruxtecan (n=9, 19%). 7 pts (15%) received a second ADC. ORR at time of best response was 38% (n=18), with 4 pts experiencing complete response (1 patient who received ADC in 1L, 3 in the 2L) & 14 experiencing partial response. 3 pts (6%) experienced stable disease, & 27 pts (56%) experienced progressive disease as best response. Median rwPFS of pts receiving ADC in the first line was 2.3 months, compared to 4.3 months in those receiving non-ADC/chemotherapy (HR 1.34; 95% CI 0.72-2.49, p=0.89). Median rwPFS of pts receiving ADC in the second line was 2.6 months, compared to 2.3 months in those receiving non-ADC/chemotherapy (HR 0.56; 0.28-1.11; p=0.10). Toxicity resulted in dose reductions in 17 pts (35%), dose delays in 14 (29%), & ADC discontinuation in 2 (4%). Conclusion: In this multi-institutional cohort of pts with metastatic MpBC, ADC treatment yielded a 38% ORR, including four complete responses. However, rwPFS was poor overall & similar between ADC & non-ADC therapy. These findings highlight the need to develop new treatment strategies for MpBC, though a subset of pts may experience meaningful response to ADC. Citation Format: S. Jacob, S. Premji, S. Fisch, A. LeVee, S. Marion, D. Schmolze, J. Mortimer, L. Huppert, D. Idossa, A. Nayak, P. Wileyto, A. DeMichele, P. D. Shah. Efficacy of antibody drug conjugates in patients with advanced metaplastic breast cancer: a multi-institutional retrospective cohort study [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 PS1-09-18.

Abstract Introduction: Metaplastic breast cancer (MpBC) represents a rare subtype, constituting <1% of all breast cancer cases. It is pathologically characterized by epithelial and mesenchymal cellular components exhibiting a basal molecular pattern, hormone receptor and HER2-negativity, and high grade. Clinically, MpBC exhibits an aggressive course with early disease progression and poor survival. Antibody-drug conjugates (ADCs) have been shown to penetrate the central nervous system (CNS); however, little is known about the response of ADCs in MpBC, particularly in patients with CNS disease. Here we aimed to describe features of CNS disease in a subset of patients (pts) who received an ADC for MpBC . Methods: We conducted a multi-institutional retrospective observational study of pts with advanced MpBC treated with ADCs at 4 NCI-designated cancer centers (abstract #A-345). This analysis includes a subset of this cohort with CNS metastases, with the aim of examining the incidence, characteristics, and treatment patterns. Clinical outcomes were evaluated for pts with information available, including CNS median progression-free survival (mPFS; defined from initiation of systemic therapy to time of further documented CNS progression or death) and median real world PFS (rwPFS; defined from time of treatment initiation to documented disease progression or death). Results: We identified 48 pts with MpBC who received an ADC. Among them, we identified 15 (31%) who developed CNS metastases. Of these, the majority (n=11, 73%) had triple-negative breast cancer, and 4 (27%) had HER2-positive breast cancer. The median age was 50 years (32-75 years). The median interval from the initial MpBC diagnosis to CNS metastasis was 13 months (0-54 months). Excluding those with de novo CNS disease, the median interval from time of metastatic diagnosis to development of CNS metastasis [mets] was 3 months (0-22 months). 4 (27%) pts had de-novo metastatic disease, of which 2 (50%) presented with CNS disease. 4 (27%) pts had screening CNS imaging prior to their diagnosis of CNS metastatic disease. At the time of CNS disease diagnosis, 9 (60%) pts had oligometastatic intraparenchymal CNS disease (defined as <5 CNS mets), 5 (33%) had diffuse (>5 CNS mets) CNS disease, and 1 (6%) had leptomeningeal and intraparenchymal disease. Most pts 14(93%) with CNS disease were symptomatic at time of diagnosis. One pt underwent resection, 9 (60%) underwent stereotactic radiosurgery (SRS), 6 (40%) underwent whole brain radiation therapy (WBRT), and 1 pt received intrathecal chemotherapy with methotrexate. The median number of lines in the metastatic setting prior to documented CNS disease was 1 (range 0-3). The majority 13 (87%) underwent a change in systemic therapy at time of CNS disease diagnosis, with 60% changing to an ADC at the time of CNS diagnosis or progression. Among pts with progression of CNS disease warranting change in systemic therapy, the median time from first CNS event to further CNS progression was 6.5 months. Median CNS PFS was 3.5 months (range 1 -74 months) and median rwPFS was 4.4 months. For those patients who used ADCs after diagnosis of metastatic CNS diagnosis (12/15), median rwPFS was 4 months. Conclusions: Within this CNS sub-cohort study, we found that 31% of pts with MpBC developed CNS metastasis. The majority of pts had neurological symptoms at diagnosis, but most pts did not undergo routing screening for CNS disease. Given the high rate of CNS mets within a short timeframe from diagnosis with poor outcomes, CNS screening should be considered. The extremely short median CNS PFS and low median rwPFS of this cohort highlight the guarded prognosis associated with MpBC. Given the small sample size of this cohort, larger studies are warranted to validate these findings. Citation Format: S. Premji, S. Jacob, A. LeVee, S. Marion, S. Fisch, L. Huppert, J. Mortimer, D. Schmolze, A. Nayak, A. DeMichele, P. Shah, R. Leon-Ferre, D. Idossa. Central nervous system disease in patients with metaplastic breast cancer receiving antibody drug conjugates: a multi-institutional study [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 PS1-09-07.

1083 Background: T-DXd and SG are both FDA-approved treatments for patients (pts) with HER2-low MBC, but little data exists on the sequential use of these ADCs. Methods: In this multicenter retrospective cohort study, we identified pts with HER2-low MBC treated sequentially with both T-DXd and SG in either order, with or without intervening therapies (IntTx), at 5 academic centers between 2020-2023. We previously reported real-world progression free survival (rwPFS) and real-world overall survival (rwOS) by HR-status and ADC sequence order. Here we provide updated rwPFS and rwOS data, as well as new subgroup analyses by age, sites of disease, and use of IntTx between ADCs for HR- and HR+ disease. Results: 84 pts with HER2-low MBC treated with both T-DXd and SG were included, including 56 pts with HR+/HER2-low MBC (66.7%) and 28 pts with HR-/HER2-low MBC (33.3%). Prior to the start of ADC1, median age was 58 yrs and 22 pts were >65 yrs (26.2%), 65 pts (77.4%) had visceral disease, and 14 pts (16.7%) had central nervous system (CNS) disease. 36 pts (42.9%) had an IntTx between ADCs. Table 1 shows updated rwPFS and rwOS data by HR-status and ADC sequence order. For pts with HR+ and HR- MBC, there was no difference in ADC1 rwPFS or ADC2 rwPFS by age ≤65 vs. >65 yr or by presence vs. absence of visceral disease. For pts with HR- MBC, ADC1 rwPFS and rwOS was shorter for pts with CNS disease vs. pts without CNS disease (rwPFS 5.4 mo (n=6) vs. 8.5 mo (n=22), p=0.03; rwOS 11.6 mo vs. 21.1 mo, p<0.01 respectively). For pts with HR+ and HR- MBC, there was no difference in ADC2 rwPFS with or without receipt of IntTx. There was no difference in time to treatment failure for first IntTx vs. ADC2 if no InTx was given. Conclusions: This is one of the largest multicenter cohorts of pts treated with sequential ADCs for HER2-low MBC. Median rwPFS was longer for ADC1 than ADC2 in all subgroups, regardless of HR-status, ADC sequence order, age ≤65 or >65 yr, presence of visceral disease, or use of IntTx. Among pts with HR-/HER2-low MBC, pts with CNS disease had shorter ADC1 rwPFS and rwOS than pts without CNS disease. [Table: see text]

Abstract Introduction: Interstitial Lung Disease (ILD) is a known adverse event associated with Antibody Drug Conjugates (ADCs), causing fibrosis of the lung. In the DESTINY-Breast 04, TROPICS-02, and ASCENT trials the rate of ILD/Pneumonitis was 12.1%, 0.4%, and 0% respectively. In these studies, the time to first cross-sectional imaging after initiation of ADC was 6 weeks. However, prior treatment with a topoisomerase-1 inhibitor ADC was not permitted in these studies, so the influence of sequential ADC treatments remains unknown. Here, we aimed to characterize the frequency and management of ILD in sequential use of ADCs in a multi-institution retrospective analysis. Methods: We identified patients (pts) with HR+/HER2-low and HR-/HER2-low MBC who had received both Trastuzumab-deruxtecan (T-DXd) and Sacituzumab govitecan (SG) monotherapy (in either order, with or without intervening therapies) who were treated at five academic centers between 2020-2023. Patients had received treatment with the ADC in either routine clinical treatment or as a prior participant on a clinical trial with ADC monotherapy. Information regarding ILD diagnosis, imaging, timing of onset, peak and resolution along with management information was collected and analyzed. Retrospective assessment of ILD toxicity was graded using CTCAE v5.0, based on available clinical and radiographic reports. Results: 10/60 pts who received ADC therapy in this multi-institutional cohort were diagnosed with ILD (all grades). No differences in age or BMI were observed in those who developed ILD versus those who did not, and 9/10 pts were White, 1 was Asian, with a median age of 59 years (47-79 years). Pertinent history in these pts included 3/10 had a prior smoking history, 8/10 had a prior cardiac or pulmonary comorbidity (including sleep apnea, lung cancer, hypertension, hyperlipidemia, thrombosis, or stroke). Prior to receiving their first ADC, 7/10 patients had metastatic disease to the lung. All 10 patients were diagnosed with ILD during treatment with T-DXd. 4 pts initially received T-DXd, then developed ILD and then upon recovery, subsequently received SG. The remaining 6 pts initially received SG (with no reports of ILD), and then received T-DXd and subsequently developed ILD. In the entire cohort, the median time from ADC initiation to first CT scan was 8 weeks (range 1-22 weeks). Within the cohort that developed ILD, the median time from initiation of T-DXd to first CT scan was also 8 weeks (range 6-13 weeks). The median time to diagnoses of ILD was 3 months after initiation of T-DXd (range 0.4-14.5 months). Dyspnea was the most common presenting symptom in 9/10 pts and at diagnosis of ILD, dyspnea was graded as III in 6/10 pts, II in 3/10 pts, and I in 1/10 pts. Diagnostic evaluation included CT chest (9/10), pulmonary consultation (8/10), pulmonary function testing (2/10), and bronchoscopy (1/10). 4/10 patients presented at their highest-grade toxicity at diagnosis. All patients stopped T-DXd treatment, 7 were hospitalized, 7 required supplemental oxygen, and 8 were prescribed steroids for treatment. Of those receiving steroids, the most common starting dose was prednisone 1 mg/kg and doses ranged from 0.5 mg/kg to 9mg/kg prednisone equivalents. No patient received a secondary immunosuppressive agent. The steroid treatment duration ranged from 1-4 months. None of the 10 pts underwent re-challenge with T-DXd and 3/10 developed grade V ILD (death). Conclusion: We observed a 16.6% incidence of all grade ILD (5% grade V ILD) with T-DXd and 0% with SG. In this small cohort study, we did not observe a clear increased risk for ILD with sequential treatment of ADCs. Practice patterns were consistent with recommended diagnostic evaluation and steroid management. Additional strategies are needed to characterize pts most at risk for developing ILD and to identify situations where re-challenge may be safe. Citation Format: Sarah Premji, Laura Huppert, Reshma Mahtani, Samantha Fisch, Naomi Dempsey, Angelina Raimonde-Taylor, Saya Jacob, Laura Quintal, Jo Chien, Michelle Melisko, Ana Sandoval-Leon, Lauren Carcas, Manmeet Ahluwalia, Natasha Harpalani, Jenna Hoppenworth, Dame Idossa, Ruta Rao, Hope Rugo, Karthik Giridhar. Interstitial Lung Disease (ILD) in Sequential Antibody Drug Conjugate (ADC) use in patients with Metastatic Breast Cancer (MBC): A Multi-Institutional experience [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 PO4-12-06.

Abstract Introduction. T-DXd is FDA-approved for patients (pts) with hormone receptor positive (HR+) or HR- HER2-low (IHC 1+ or 2+, ISH-) MBC and SG is FDA-approved for pts with HR+/HER2- and triple negative MBC. However, several outstanding questions impact the use of these drugs in clinic, including: 1) what is the efficacy and safety of these agents in real-world populations with diverse pt characteristics not well represented in the pivotal phase III trials, and 2) what is the impact of sequential treatment with ADCs on the efficacy and safety of these agents. Methods. In this multicenter retrospective cohort study, we identified pts with HR+/HER2-low and HR-/HER2-low MBC who had received both T-DXd and SG monotherapy (in either order, with or without intervening therapies) treated at 5 academic centers between 2020-2023. Pts received treatment per standard of care or on a clinical trial with ADC monotherapy. We describe pt demographic and clinical characteristics, treatment history, key safety parameters, and response and survival data by HR+ status and ADC sequence order. Results. Sixty pts with MBC treated sequentially with T-DXd and SG were included in this analysis, including 45 pts with HR+/HER2-low MBC (75.0%) and 15 pts with HR-/HER2-low MBC (25.0%). Most pts were female (n=59; 98.3%), non-Hispanic (n=49, 81.7%), and white (n=43, 71.7%). Median age at start of ADC #1 was 56.6 years (range 23-82). Prior to treatment with ADC #1, most pts had visceral disease (n=45, 75.0%) and 16 (26.7%) had central nervous system metastases. Among pts with HR+/HER2-low MBC, median time from MBC diagnosis to treatment with ADC #1 was 49.0 months, with 4 median lines of prior therapy in the metastatic setting (2 endocrine, 2 chemo). Approximately half of the HR+ pts received T-DXd prior to SG (n=22, 48.9%; median 3.0 prior lines of therapy for MBC, range 1-9) while the other half received SG prior to T-DXd (n=23, 51.1%; median 4.5 prior lines of therapy for MBC, range 1-10). 44% (n=20) received an intervening therapy between ADCs. For HR+ pts who received T-DXd prior to SG, response and survival data is as follows for T-DXd and SG respectively: Overall response rate (ORR) [54.5% and 21.1%], time to next treatment (TTNT) [4.3 mo and 1.6 mo], and real-world overall survival (rwOS) [19.8 mo and 4.9 mo]. For HR+ pts who received SG prior to T-DXd, response and survival data is as follows for SG and T-DXd respectively: ORR [78.3% and 42.9%], TTNT [8.6 mo and 2.8 mo], and rwOS [22.3 mo and 7.3 mo]. Among pts with HR-/HER2-low MBC, median time from MBC diagnosis to treatment with ADC #1 was 8.2 months with 2 median lines of prior therapy in the metastatic setting (2 chemotherapy); 66.7% (n=10) received prior immunotherapy. Most HR- pts received SG prior to T-DXD (n=14, 93.3%) and 40.0% (n=6) received an intervening therapy between ADCs. For HR- pts who received SG prior to T-DXd, response and survival data is as follows for SG and T-DXd respectively: ORR [64.3% and 38.5%], TTNT [6.2 mo and 2.7 mo, and rwOS [15.7 mo and 6.5 mo]. In terms of key safety parameters during treatment with T-DXd, 13.3% of pts (8/60) required a dose reduction. 16.7% (10/60) were diagnosed with interstitial lung disease (ILD)/pneumonitis of any grade including 3 pts with grade 3-4 ILD (5.0%) and 3 pts with grade 5 ILD (5.0%). During treatment with SG, 40.0% of pts (24/60) required a dose reduction. 83.3% (50/60) received growth factor support (24 pts primary prophylaxis; 26 pts secondary prophylaxis); 9 pts (15%) required treatment delay due to neutropenia. Conclusion. This study represents the largest multicenter series to date of pts treated with sequential ADCs for HR+/HER2-low or HR-/HER2-low. ORR was higher and TTNT was longer for ADC #1 than ADC #2 in all subgroups, regardless of HR+ status and ADC sequence order. An additional ~30 pts will be reported at time of final analysis. Future prospective studies are planned to further clarify the efficacy and safety of sequential ADC use and to identify biomarkers of response and resistance. Key demographic, clinical and treatment characteristics in pts with HR+ and HR- HER2-low MBC treated sequentially with T-DXd and SG (in either order, with or without intervening therapies) Abbreviations: T-DXd (trastuzumab deruxtecan), SG (sacituzumab govitecan), MBC (metastatic breast cancer), ADC (antibody drug conjugate), HR (hormone receptor), HER2 (human epidermal growth factor receptor 2), CNS (central nervous system), ET (endocrine therapy), ORR (overall response rate), TTNT (time to next treatment), rwOS (real world overall survival), CI (confidence interval) * Several pts on ADC #2 with ongoing treatment and first scan pending, hence smaller denominator for response assessment Citation Format: Laura Huppert, Reshma Mahtani, Samantha Fisch, Naomi Dempsey, Sarah Premji, Angelina Raimonde-Taylor, Saya Jacob, Laura Quintal, Jo Chien, Michelle Melisko, Ana Sandoval-Leon, Lauren Carcas, Manmeet Ahluwalia, Natasha Harpalani, Jenna Hoppenworth, Dame Idossa, Ruta Rao, Karthik Giridhar, Hope Rugo. Multicenter retrospective cohort study of the sequential use of the antibody-drug conjugates (ADCs) trastuzumab deruxtecan (T-DXd) and sacituzumab govitecan (SG) in patients with HER2-low metastatic breast cancer (MBC) [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 PS08-04.

611 Background: Patient reported outcomes (PROs) capture direct feedback from patients in clinical trials. The NIH Patient-Reported Outcomes Measurement Information System (PROMIS) is an open source and validated PRO platform. Data on PROMIS score trajectories over time for breast cancer patients undergoing neoadjuvant chemotherapy (NAC) are limited. Methods: We administered paper surveys to patients enrolled on the I-SPY2 trial, a multicenter, randomized phase 2 trial comparing novel agents to standard NAC in high-risk breast cancer. PRO domains included PROMIS Physical Function, Anxiety, Depression, Applied Cognition and Fatigue. Surveys were administered at baseline (post-consent), C1D1, inter-regimen (~12 wks into NAC), pre-surgery and at 1, 6, 12, and 24 months post-surgery. Responses were scored using the HealthMeasures Scoring Service to generate a standardized T score, with a score of 50 representing the general US population mean. Higher Anxiety, Depression and Fatigue scores represent worse symptoms; higher Physical Function and Applied Cognition scores represent better symptoms. We calculated average scores by time-point and compared changes from baseline to various grouped time points using a paired t-test. Results: From 1/2012 to 7/2020, 1631 patients enrolled in I-SPY 2 with 959 completing the baseline survey. 62% had at least two “on-treatment” surveys, and 52% had at least one follow-up time-point. Average baseline PROMIS scores for Physical Function, Anxiety, Depression, Applied Cognition and Fatigue were 46.7, 55.1, 47.2, 53.3 and 46.0 respectively. Between baseline and the latest on-treatment time point we observed improvement in Anxiety (-5.2) and worsening in Physical Function, Applied Cognition and Fatigue (-5.4, -6.9 and +8.2 respectively). Between baseline and the latest post-surgery time point, we saw improved Anxiety (-5.9) and worsened Physical Function, Applied Cognition and Fatigue (-5.9, -3.6 and +4.3). Depression changed minimally. Conclusions: Using PROMIS, patients on I-SPY2 experienced worse Physical Function, Applied Cognition and Fatigue but improved Anxiety during and after treatment compared to baseline. While changes in Applied Cognition and Fatigue recovered partially after treatment, Physical Function scores did not, suggesting potential for longer term impact on quality of life. Clinical trial information: NCT01042379 . [Table: see text]

3036 Background: The presence of HER2 expressing (HER2+) circulating tumor cells (CTCs) occurs often in metastatic breast cancer (MBC) patients (pts). We have previously showed that the ratio among CTCs expressing high level of HER2 and the total number of HER2+ CTCs (circulating HER2 ratio, cHer2 ratio) has a prognostic role in MBC patients. Here we further investigate the role of the cHER2 ratio in the process of metastatic spread. Methods: Under IRB-approved study we prospectively analyzed blood samples of patients with MBC enrolled before starting a new line of therapy. Samples were collected from pts treated at Northwestern University (Chicago, IL) between 2016 and 2020. CTCs were enumerated through CellSearch (Menarini Silicon Biosystems, Bologna, Italy) and characterized for HER2 expression using the CellSearch CXC Kit. HER2+ CTCs were divided in 3 different categories (1+,2+,3+) leaning on fluorescence intensity. Pts with <5 CTCs (stage IV indolent) were excluded from the analysis. The cHER2 ratio, defined as the sum of 2+ CTCs and 3+ CTCs divided by the total number of HER2+ CTCs, was used to split the remaining pts in 2 different cohorts: cHER2 ratio high (> 0.75) (cHER2high) and cHER2 ratio low (≤0.75) (cHER2low). The frequency of each metastatic site (i.e. liver, lung, central nervous system, bone, lymph nodes, skin/soft tissue, serosa) and the total number of different sites involved (1-7, ≤2 and >2 sites) were compared among the two sub-populations and analyzed through Fisher exact test. Results: Out of 98 pts enrolled, 77 were classified as cHER2low and 21 as cHER2high. We observed a higher frequency of oligometastatic pts (≤2 sites involved) in the cHER2high cohort (16, 76%), compared to only 29 (37%) in the cHER2low (p<0.005). Moreover, the cHER2 ratio was associated with a tropism toward specific sites of disease spread with higher incidence of liver, lung and lymph nodes metastases in the cHER2low cohort (p<0.05). No other statistical associations were observed in respect of specific organ tropism. The frequency of involvement for each metastatic site among the two cohorts are reported in the table. Conclusions: Measuring CTCs enumeration and HER2 expression we identified two cohorts, cHER2high and cHER2low, associated with distinct patterns of metastatic spread. The cHER2low pts were correlated to multiple sites of metastatic involvement, with particular tropism toward liver, lung and lymph nodes. These results confirm the prognostic role of the cHER2 ratio, suggesting a peculiar biological meaning of the HER2+ 1+ CTCs.[Table: see text]