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545 Background: ILC is characterized by loss of E-cadherin expression, with distinct biological and clinical features, and is often perceived to be less sensitive to chemotherapy compared with IDC. Oncologists and pts may face a treatment dilemma regarding the benefits of adjuvant chemotherapy in pts with lower biologic risk but higher anatomic risk (N2/N3), stage III ILC. In this study, we sought to compare the benefit of adjuvant chemotherapy in pN2/N3 ILC compared with IDC. Methods: We used the National Cancer Database (NCDB) to identify adults with primary, non-metastatic, ER-positive/HER2-negative invasive breast cancer diagnosed between 2010 and 2022 who underwent upfront surgery. Patients receiving neoadjuvant systemic therapy were excluded. Analyses were limited to pathologic stage I–III disease with known nodal involvement (N2–N3) and tumor category (T1–4). Propensity score matching (1:3, caliper 0.2; using R 4.5.1) was performed to balance age, sex, race, insurance status, grade, pathologic stage, nodal category, tumor category, Charlson-Deyo comorbidity score, and year of diagnosis. Overall survival (OS) was assessed using Kaplan–Meier methods and Cox proportional hazards models used to estimate hazard ratios (SPSS v28). Results: After propensity matching, we analyzed 28,115 pts with pN2/N3 disease (ILC 9,603 and IDC 18,512). Upstaging from cN0 to pN2/3 was higher for ILC than IDC (20.3% vs 13.3%, p<0.001). ILC pts were more likely to undergo mastectomy compared to IDC (80.2% vs 71.2%, p<0.001). Receipt of adjuvant chemotherapy for pN2/N3 disease was similar between IDC and ILC (78.0% vs 78.4%, p=0.37), as was use of adjuvant radiation and endocrine therapy. Among patients receiving chemotherapy, treatment was associated with a 65% reduction in death in ILC (HR 0.35, 95% CI 0.32–0.38, p<0.001) and a 73% reduction in IDC (HR 0.27, 95% CI 0.26–0.29, p<0.001), compared with no chemotherapy. 5-year OS among chemotherapy-treated patients was lower for ILC compared with IDC (HR 1.4, 95% CI 1.33-1.49; p<0.001, Table 1). In contrast, no OS difference was observed between ILC and IDC among patients who did not receive chemotherapy (HR 1.03, 95% CI 0.96-1.11; p=0.38). Chemotherapy was associated with higher 5-year OS in both IDC (87.7% vs 58.9%) and ILC (84.3% vs 59.2%). Conclusions: Adjuvant chemotherapy was associated with a substantial improvement in 5-year OS among patients with pN2/N3 disease in both IDC and ILC. Pts with ILC and extensive nodal involvement benefit from adjuvant chemotherapy. 5-year survival of IDC and ILC. IDC (18,512) ILC (9,603) No Chemotherapy (4,078) Adjuvant Chemotherapy (14,434) No Chemotherapy (2,071) Adjuvant Chemotherapy (7,532) pN2 (18,669) 62.8% 90.1% 64.4% 87.6% pN3 (9,446) 48.3% 82.2% 51.4% 79.4% pN2/pN3 Combined (28,115) 58.9% 87.7% 59.2% 84.3% P <0.001, log rank.

Abstract Background: Clinical benefit with PARP inhibitors (PARPi) has been demonstrated in patients (pts) with HER2-negative (HER2−) metastatic breast cancer (mBC) and germline or tumor mutations in BRCA1 or BRCA2 (g/tBRCAm). Understanding real-world PARPi use and its impact on clinical outcomes may improve the treatment of pts with BRCAm HER2− mBC. Methods: This retrospective study captured data from US pts aged ≥18 years diagnosed with HER2− mBC from January 12, 2018, to March 31, 2024, in the deidentified electronic health record-derived Flatiron Health Research Database. PARPi use and outcomes were described by tumor subtype (hormone receptor-positive [HR+]/HER2− mBC or triple-negative mBC [mTNBC]), g/tBRCA status, disease stage at diagnosis (de novo or recurrent), line of therapy (LoT), and prior treatments. Real-world overall survival (rwOS) by PARPi use was estimated using the Kaplan-Meier method. Results: Of 848 pts with gBRCAm mBC, 352 (42%) received PARPi (Table), with consistent PARPi initiation rates of 42%-48% from 2018-2022. PARPi was initiated in 223/566 (39%) pts with gBRCAm HR+/HER2− mBC, 125/275 (45%) pts with gBRCAm mTNBC, and 4/7 (57%) pts with unknown tumor subtype. Among 304 pts with gBRCAm who had received ≥3 LoT by the end of follow-up, 93/225 (41%) pts with HR+/HER2− mBC and 18/78 (23%) pts with mTNBC received PARPi in the third LoT or later (3L+); 50/103 (49%) pts with de novo mBC and 54/184 (29%) pts with recurrent mBC received PARPi in 3L+. PARPi was also initiated in 13/231 (6%) pts with gBRCA variants of uncertain significance (VUS) and 176/662 (27%) pts with tBRCAm and non-gBRCAm/unknown gBRCAm status. Among 539/1573 (34%) pts with g/tBRCAm who received PARPi, 167 had not received prior chemotherapy in any setting; 40 of these pts (39 with HR+/HER2− mBC and 1 with mTNBC) received PARPi in 3L+. With a median follow-up of 17.0 months from initiation of 1L therapy, median rwOS was numerically longer among pts with gBRCAm who received PARPi versus pts who did not (HR+/HER2− mBC: 39.3 months [95% CI: 35.5-46.8], n=208 vs 24.2 months [95% CI: 21.4-33.0], n=259; mTNBC: 27.6 months [95% CI: 18.0-41.7], n=119 vs 16.9 months [95% CI: 14.5-31.9], n=81). Among pts with tBRCAm who were negative for gBRCAm, median rwOS was numerically longer in pts who received PARPi versus pts who did not. Conclusions: Pts with HR+/HER2− mBC had slightly lower rates of PARPi use, and received PARPi later, than pts with mTNBC. Although improved efficacy with PARPi use in earlier LoT has been demonstrated, many pts first received PARPi in 3L+, suggesting unmet potential to ensure timely testing and optimize treatment. Although immortal time bias and other factors should be considered, rwOS was numerically longer in pts with BRCAm HR+/HER2− mBC and with BRCAm mTNBC who initiated PARPi versus pts who did not. Further research into PARPi use and survival trends in pts with BRCAm and/or other actionable biomarkers in mBC is needed. Citation Format: S. Yadav, Q. Li, Z. Tan, K. E. Mishkin, J. F. Hayes, X. Xu, F. J. Couch. Real-world PARP inhibitor use and clinical outcomes in US patients with HER2-negative 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 PS2-02-08.

Abstract Background: Incorporation of Polygenic Risk Scores (PRS) can refine traditional breast cancer (BC) risk assessment models to provide precise estimates of BC risk. However, the impact of such an integrated model on BC risk estimates and clinical decision-making related to BC screening and preventive strategies in germline pathogenic variant (PV) carriers is not fully understood. Methods: The GENRE-2 is a prospective single-arm multisite clinical trial (NCT04474834) incorporating 313-PRS into standard BC risk assessment models to determine the impact of PRS on risk estimates and clinical decisions on prevention and screening. All women received pre- and post-PRS BC risk estimates and completed surveys on their screening and cancer prevention decisions before and after integrating PRS estimates. Herein, we report on the impact of integrating PRS into CanRisk-based BC risk estimates among women enrolled in GENRE-2 due to PVs in ATM, BRCA1, BRCA2, CHEK2, or PALB2. Women were categorized into average risk (&lt;20%), moderate risk (20-40%), or high risk (&gt;40%) for BC based on clinically relevant lifetime risk thresholds for supplemental MRI screening and risk-reducing bilateral mastectomies. Changes in categories of lifetime BC risk estimates were then evaluated before and after integration of PRS. Impact of PRS on patient decisions to undertake screening or preventive action (medication or prophylactic mastectomy) was evaluated based on pre- and post-PRS surveys. Results: Between 2020 and 2025, 933 women were enrolled, 633 received PRS results and completed a survey to date. Of those who received PRS results, 214 (33.8%) were PV carriers (ATM: 24, BRCA1: 54, BRCA2: 73, CHEK2: 54 and PALB2: 9). Among PV carriers, the CanRisk-based median 10-year and lifetime pre-PRS risk estimates were 6.0% and 23.9% for ATM, 22.5% and 77.5% for BRCA1, 17.9% and 77.6% for BRCA2, 7.1% and 26.6% for CHEK2, and 16.6% and 42.4% for PALB2, respectively. A total of 7 (29.2%) ATM PV carriers had a shift in lifetime BC risk categories after integration of PRS, with 1 (4.2%) shifting from average to moderate-risk, 3 (12.5%) shifting from moderate to average-risk category, and 3 (12.5%) shifting from moderate to high-risk category. Among CHEK2 PV carriers, 9 (16.7%) had a shift in lifetime risk categories, with 4 (7.4%) shifting from moderate to average-risk, 2 (3.7%) shifting from moderate to high-risk, and 3 (5.6%) shifting from high to moderate-risk. None of the BRCA1 and 4.1% of BRCA2 PV carriers had a shift in lifetime risk categories after PRS integration. Only 1 (11.1%) PALB2 PV carrier had a change in lifetime risk category after integration of PRS, although this was limited by a small sample. A significantly higher proportion of PV carriers with a high lifetime risk intended to take preventative action compared to the PV carriers with average lifetime risk (41.4% vs. 20.0%, p=0.007). Conclusions: Integration of PRS into BC lifetime risk estimates led to a clinically meaningful change in risk categories in 29.2% of ATM PV carriers and 16.7% of CHEK2 PV carriers, but in &lt;5% of BRCA1 or BRCA2 PV carriers. These findings suggest that PRS may be helpful for BC risk stratification in moderate-risk genes such as ATM and CHEK2 but may have limited clinical utility in high-risk genes such as BRCA1 or BRCA2. Citation Format: S. Yadav, C. Klassen, D. Stan, J. Fraker, S. Sahni, S. A. Khan, L. Khatri, C. Vachon, D. Schaid, J. P. Sinnwell, E. Carlson, L. Hasadsri, F. J. Couch, S. Pruthi. Impact of Polygenic Risk Scores on Breast Cancer Risk Assessment and Clinical Decision Making in Carriers of Germline Pathogenic Variants in ATM, BRCA1, BRCA2, CHEK2, and PALB2: Results from the Prospective Multisite GENRE-2 Clinical Trial [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 PD4-04.

Abstract Immune checkpoint inhibitor–associated immune thrombocytopenia (ICI-ITP) has been described in case reports and small case series, but comprehensive data on its incidence, risk factors, clinical features, treatment, and outcomes are lacking. We reviewed medical records of all adults initiating ICI therapy between 2016 and 2023 at 29 US hospitals across 7 major cancer centers to identify patients with ICI-ITP. Multivariable logistic regression was used to identify risk factors, and Cox modeling was performed to assess the association between ICI-ITP, its severity, and mortality. Among 86 467 patients, ICI-ITP occurred in 214 (0.25%). Independent risk factors included lower baseline platelet count, combination ICI therapy, stage IV cancer, and additional immune-related adverse events. ICI-ITP occurred at a median of 8 weeks (interquartile range [IQR], 4-18) after ICI initiation, with a median nadir platelet count of 41 × 109/L (IQR, 17 × 109/L to 64 × 109/L). Patients were treated with glucocorticoids (n = 106 [49.5%]), immune globulin (n = 39 [18.2%]), and thrombopoietin receptor agonists (n = 29 [13.6%]). Recovery occurred in 161 patients (75.2%) at a median of 2.3 weeks (IQR, 1.0-5.3). Of 76 patients rechallenged with ICIs, 23 (30.3%) developed recurrent ICI-ITP. ICI-ITP and its severity were associated with higher all-cause mortality, with a nearly threefold increase in risk among patients with severe ICI-ITP than those without ICI-ITP (adjusted hazard ratio, 2.96 [95% confidence interval, 2.14-4.08]). These findings establish ICI-ITP as a rare but clinically significant complication of ICI therapy, provide, to our knowledge, the first large-scale description of its risk factors and clinical course, and underscore the importance of timely recognition and management.

Abstract Background: Routine laboratory testing prior to chemotherapy administration is a cornerstone of hematology and oncology practice, aimed at ensuring the safety and efficacy of treatment. However, over time, standardized protocols may accumulate excessive or low-yield laboratory tests that offer limited value to clinical decision-making. In 2018, Mayo Clinic implemented standardized treatment protocols using Epic Beacon, an electronic health record module that integrates chemotherapy regimens with associated laboratory testing and clinical workflows. While well-intentioned, these protocols may include redundant tests that delay treatment initiation, increase patient discomfort and anxiety, and burden providers with excessive in-basket communications. We hypothesize that many laboratory tests currently embedded within prechemotherapy workflows are unnecessary and can be safely omitted without compromising patient care. Methods: We conducted a retrospective cohort study evaluating the pre-treatment laboratory testing associated with the R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone) chemotherapy protocol within the Mayo Clinic Rochester Division of Hematology. The study included 100 patients diagnosed with diffuse large B-cell lymphoma who received treatment between January 1 and December 31, 2024. Patients were excluded if they had incomplete medical records or received treatment outside the Mayo Clinic system. Data was abstracted via chart review using the Mayo Data Explorer. We analyzed complete blood counts (CBC), which include 12 individual tests, and comprehensive metabolic panels (CMP), which include 16 individual tests, obtained prior to each treatment cycle. For each cycle, we assessed the proportion of abnormal laboratory results and the proportion of abnormal results deemed clinically relevant which were defined as those that prompted a treatment delay, dose reduction or early termination of a cycle. Results: The cohort comprised 100 patients with a mean age of 68.2 years (SD 13.4) and a median age of 71 years (IQR 58.75–77); 57 were male and 43 were female. Based on available documentation, disease stage was classified as limited (stage I/II; n=41) or extensive (stage III/IV; n=59). A total of 519 R-CHOP cycles were administered, including 419 subsequent cycles (cycles 2–6). Fifteen patients discontinued treatment early, although none of the discontinuations were attributable to abnormalities in pre-infusion laboratory testing. Among the 419 subsequent cycles, 34 (8.1%) experienced treatment delays, with only one delay resulting from a clinically significant laboratory abnormality (hyperglycemia). Additionally, 23 patients underwent regimen modification (dose reduction or drug holding), but none of these were due to pre-infusion lab abnormalities.Of the 411 comprehensive metabolic panels (CMPs) obtained prior to these cycles, 315 (76.6%) contained at least one abnormal value, yielding a total of 786 abnormal results. Similarly, 405 of 415 (97.6%) complete blood counts (CBCs) demonstrated at least one abnormality, generating 2,696 abnormal values in total. Despite the high frequency of abnormal findings, the overall clinical yield was minimal, with only 1 of 826 pre-infusion laboratory panels (0.12%) leading to a modification in clinical management. Conclusion: Routine pre-infusion laboratory testing prior to R-CHOP chemotherapy frequently identifies abnormal results. However, these abnormalities are rarely clinically significant and do not affect treatment decisions. These findings support the reconsideration of current testing protocols to reduce unnecessary testing, enhance workflow efficiency, and minimize patient and provider burden without compromising safety.

Abstract Abstract Introduction: Leukemia, a heterogeneous group of hematologic malignancies, has established associations with modifiable risk factors such as tobacco use. Despite the widespread implementation of tobacco control measures over the past three decades, disparities persist in tobacco-attributable leukemia mortality across sex and socio- demographic strata. This study aimed to quantify and compare long-term global and regional trends in mortality due to tobacco-associated leukemia between 1990 and 2021, with a focus on sex-based and income-level disparities. Methods: We obtained age-standardized mortality rates (ASMRs) for leukemia attributable to tobacco use from the Global Burden of Disease (GBD) 2021 dataset for 204 countries and territories. ASMRs were analyzed for the years 1990 and 2021 and stratified by sex (male, female, both) and socio-demographic index (SDI) regions (high, high-middle, middle, low- middle, low). Temporal trends were assessed using Average Annual Percent Change (AAPC) with corresponding 95% confidence intervals (CI). Additionally, univariate linear regressions by location were conducted to quantify associations between time and mortality. Results: Globally, tobacco-related leukemia mortality decreased substantially between 1990 and 2021. The overall ASMR declined from 0.64 to 0.40 per 100,000 population (AAPC: –1.51%; 95% CI: –1.59 to –1.43). Sex-disaggregated data revealed a more favorable reduction in females (from 0.23 to 0.12; AAPC: –2.25%; 95% CI: –2.41 to –2.09) compared to males (from 1.20 to 0.77; AAPC: –1.45%; 95% CI: –1.51 to –1.39), suggesting persistent gender disparities in tobacco exposure and/or access to care. These trends were statistically significant (p &lt; 0.001), and global univariate regression confirmed a significant negative slope (–0.0088; p = 0.021). Marked regional differences emerged by SDI status. High-SDI countries experienced the steepest declines in mortality. In these regions, ASMRs dropped from 1.16 to 0.69 among both sexes combined (AAPC: –1.70%; 95% CI: –1.80 to –1.61), with females improving from 0.56 to 0.31 (AAPC: –1.90%; 95% CI: –2.03 to –1.76) and males from 2.07 to 1.17 (AAPC: –1.88%; 95% CI: –1.96 to –1.80). The associated regression slope (–0.0183) was statistically significant (p = 0.0014), with an R² of 0.10, indicating a strong temporal association. High-middle SDI regions showed moderate progress: ASMRs declined from 0.62 to 0.45 among both sexes (AAPC: –0.99%; 95% CI: –1.10 to –0.88). Reductions were steeper in females (0.12 to 0.07; AAPC: –1.32%; 95% CI: –1.55 to –1.09) than in males (1.40 to 0.96; AAPC –1.19%; 95% CI: –1.29 to –1.09). However, regression slopes were not statistically significant (p = 0.18), suggesting heterogeneous trends within this group. Low-SDI regions, in stark contrast, exhibited minimal improvements. Between 1990 and 2021, ASMRs decreased marginally from 0.098 to 0.074 (AAPC: –1.01%; 95% CI: –1.10 to –0.91), with male mortality decreasing from 0.17 to 0.12 (AAPC: –1.22%; 95% CI: –1.32 to –1.13) and female rates from 0.037 to 0.027 (AAPC: –0.88%; 95% CI: –1.04 to –0.72). However, the regression slope (–0.00084) was not statistically significant (p = 0.17), and the effect size (R² = 0.02) suggested only a weak temporal association. Middle and low-middle SDI countries also demonstrated underwhelming progress. In low- middle SDI settings, the combined-sex ASMR dropped from 0.21 to 0.16 per 100,000, with a weak negative slope (–0.0012; p = 0.43), and an AAPC of –0.83% (95% CI: –0.95 to –0.71). These results highlight stagnation and growing inequities in health burden mitigation. Conclusion: From 1990 to 2021, global mortality due to tobacco-attributable leukemia significantly declined, with the greatest improvements seen in high-SDI countries and among females. However, regions with lower income levels lagged, showing minimal or no significant decline in mortality despite decades of global tobacco control efforts. The pronounced disparities by sex and socioeconomic status underscore the need for context- specific, equity-focused tobacco cessation initiatives and leukemia screening programs, especially in underserved populations. Without urgent intervention, the global burden of leukemia attributable to tobacco may continue to disproportionately affect those with the fewest resources and weakest health infrastructure.

Abstract INTRODUCTION Immune checkpoint inhibitors (ICIs) have emerged as a cornerstone of cancer therapy. However, despite their efficacy, ICIs can cause a unique spectrum of autoimmune toxicities known as immune-related adverse events (irAEs). In contrast to irAEs involving other organ systems, hematologic irAEs such as ICI-associated immune thrombocytopenia (ICI-ITP) are less common. As a result, existing data on ICI-ITP are largely confined to isolated case reports, single-center case series, and pharmacovigilance databases lacking granular clinical data. To address this key knowledge gap, we sought to comprehensively characterize the incidence, risk factors, clinical features, treatments, and outcomes associated with ICI-ITP. METHODS We performed a multicenter cohort study of adult patients who initiated ICI therapy at 29 hospitals across 7 major cancer centers in 11 geographically diverse states in the US between 2016-2023. ICI-ITP was defined as a decline in platelet count to &lt;100 x109/L in the absence of an alternative more plausible etiology of thrombocytopenia. Patients with hematologic malignancies were excluded, as were those who received cytotoxic chemotherapy within 30 days prior to thrombocytopenia onset. For each patient identified as having ICI-ITP, we collected data on demographics, comorbidities, medications, laboratory values, treatments, and outcomes. All data were extracted by manual chart review. To identify risk factors for ICI-ITP and to examine its association with death, for each case of ICI-ITP we also collected data on two control patients who initiated ICI therapy at the same site and in the same year but without development of ICI-ITP. We used multivariable logistic regression to identify independent risk factors for ICI-ITP and its recovery (the latter defined according to criteria established by the ITP International Working Group). We used a multivariable Cox model to examine the association between ICI-ITP and its severity with all-cause mortality. RESULTS We identified a total of 214 patients who developed ICI-ITP among 86,648 examined (0.25%). The incidence was highly consistent across sites (range, 0.15–0.30%). Risk factors for ICI-ITP included simultaneous receipt of two different classes of ICIs, additional irAEs, and a lower baseline platelet count. ICI-ITP developed at a median of 8 weeks (IQR, 4–18) following ICI initiation. The median nadir platelet count was 41 x109/L (IQR, 17–64). Six out of 214 patients (2.8%) developed a major bleed, and 16 patients (7.5%) developed a clinically relevant non-major bleed. Cell-bound anti-platelet antibody testing was positive in 6 of 8 patients (75.0%) for whom it was assessed, and median circulating thrombopoietin levels (201 pg/mL [IQR, 178–295]) were similar to those seen in primary ITP. Treatments used included glucocorticoids (49.5%), immune globulin (18.2%), and thrombopoietin receptor agonists (13.6%). Overall, 161 patients (75.2%) recovered from ICI-ITP at a median of 2 weeks (IQR, 1–5) following ICI-ITP onset. Predictors of recovery included additional irAEs and a higher nadir platelet count. Treatment response was observed in 57.0%, 56.4%, and 58.3% of patients within 60 days following initiation of glucocorticoids, immune globulin, and thrombopoietin receptor agonists, respectively. Of 76 patients rechallenged with an ICI, 23 (30.3%) developed recurrent ICI-ITP at a median of 9 weeks (IQR, 2–15); 17 of these 23 patients (73.9%) recovered. Finally, ICI-ITP and its severity were monotonically associated with a higher risk of death (adjusted hazard ratio 2.96 [95% CI, 2.14–4.08] for those with severe ICI-ITP compared to those without ICI-ITP). CONCLUSION In this multicenter study involving patients treated with ICIs at 29 hospitals across the US, we identified 214 patients with ICI-ITP. For the first time, we characterize in detail the incidence, risk factors, clinical features, treatments, and outcomes of ICI-ITP, a relatively novel disease entity. We found that more than half of patients responded to conventional ITP-directed therapies, and that most patients rechallenged did not develop recurrent ICI-ITP. We also found that ICI-ITP was independently associated with an increased risk of death, including a nearly 3-fold increased risk in those with severe ICI-ITP. These findings highlight ICI-ITP as a rare but clinically significant complication of ICI therapy that hematologists must be equipped to recognize and manage.

Abstract Background: Atypical Hemolytic Uremic Syndrome (aHUS) remains a diagnostic challenge as it shares overlapping features of Thrombotic Thrombocytopenic Purpura (TTP) and Shiga-toxin mediated HUS (STM-HUS). It is caused by complement activation in the alternative pathway and is mostly related to genetic defects in complement-related factors or acquired autoantibodies. Early recognition and treatment have excellent outcomes. Case Presentation: A 74-year-old female with Hypertension presented with a 3-week history of non-bloody diarrhea and was found to have acute kidney injury (AKI) with creatinine 5.27 mg/dL (baseline 0.5), anemia (7.5 g/dL), and thrombocytopenia (123×10⁹/L) and normal liver function. CT imaging of the abdomen revealed uncomplicated sigmoid diverticulitis and mesenteric lymphadenopathy. She was treated with intravenous fluids and started on antibiotics with ceftriaxone and metronidazole for diverticulitis. Despite fluid resuscitation, renal function deteriorated, necessitating initiation of intermittent hemodialysis. Due to anemia, thrombocytopenia and AKI further workup with peripheral smear pursued showed schistocytes, helmet cells, and keratocytes. Hemolysis labs showed LDH 1433 U/L, undetectable haptoglobin, and a negative direct Coombs test. Methylmalonic acid level was normal. Homecystine level was elevated. These findings were consistent with microangiopathic hemolytic anemia. Coagulation profile was normal. Given concern for TTP, ADAMTS13 was obtained but returned at 68%, ruling out TTP. Shiga toxin PCR was negative, ruling out STM-HUS. Complement level checked showed low C3 and C4, suggesting complement activation and consumption. Total complement, Factor 8, factor B, monoclonal protein were within normal. A renal biopsy was initially postponed due to uncontrolled hypertension. Eculizumab was started. Renal biopsy later done confirmed aHUS. Following initiation of eculizumab, the patient's renal function progressively improved, and she was able to discontinue hemodialysis. Laboratory markers of hemolysis stabilized, with normalization of LDH, haptoglobin, homocystine and complement. She completed the induction phase of eculizumab and entered a long-term monitoring phase, with labs every 2 weeks for 6 months, then monthly for 36 months. No relapses were noted to date and is off dialysis. Conclusion: Differentiating aHUS from TTP and STM-HUS is critical, as management strategies differ significantly. Prompt initiation of eculizumab can reverse renal injury and prevent further organ damage.

572 Background: Neoadjuvant endocrine therapy (NET) is sometimes used to shrink hormone receptor-positive (HR+) breast cancers to improve breast conservation rates and reduce axillary nodal burden. At the beginning of the COVID-19 pandemic, several organizations endorsed NET use to mitigate the harm of surgery delay when cancer operations were less available due to infection transmission concerns. However, the real-world patterns of NET during this period are understudied. This study investigated the alteration of NET utilization patterns during the COVID-19 pandemic in the United States using the National Cancer Database (NCDB). Methods: We identified patients diagnosed with stage I-III invasive HR+/human epidermal growth factor receptor 2-negative (HER2-) breast cancer between 2018-2022 in the NCDB. Estrogen receptor and/or progesterone receptor positivity was required for inclusion in the cohort. Receipt of NET was defined as initiation of endocrine therapy ≥ 14 days before the patient’s first surgical procedure. The study cohort generation and statistical analysis were conducted using Stata and R 4.4.3. A two-tailed p value < 0.05 was considered statistically significant. Results: 495,098 patients were included in the cohort, 195,371 in 2018-2019 (pre-pandemic), 91,686 in 2020 (early pandemic), 106,157 in 2021 (mid-pandemic), and 101,884 in 2022 (late pandemic). NET utilization was increased in the early pandemic compared to the pre-pandemic (seen in 5.8% vs 2.4% of the cohort, Chi-square p value < 0.001), but this use fell back to 3.4% in the mid-pandemic and 3.5% in the late-pandemic. The median (IQR) duration of NET was 15.7 (6.4-26.6) weeks in the pre-pandemic, 9.3 (5.4-18.7) weeks in the early pandemic, 13.2 (5.8-25.7) weeks in the mid-pandemic, and 12.0 (6-24.6) weeks in late pandemic (Kruskal-Wallis p value = 0.001). The transient increase in NET utilization during the early pandemic was more pronounced among patients with tumors < 5 cm and node-negative disease. Conclusions: Our study identified a significant shift in the utilization of NET for HR+/HER2- breast cancer during the COVID-19 pandemic. Pandemic-era NET policies produced a short-lived practice change that was only partially sustained once surgical access normalized. NET utilization (%) by subgroup and year for stage I-III HR+/HER2- breast cancer. Variable Category 2018-2019 2020 2021 2022 Overall NET Use 2.4 5.8 3.4 3.5 Age Group (years old) <50 2.2 4.9 3.9 4.0 >=50 2.4 6.0 3.3 3.4 Tumor Size <5 cm 2.0 5.5 2.9 3.1 >=5 cm 9.0 9.7 11.2 11.6 Histology Subtype Ductal 2.2 5.5 3.3 3.4 Lobular 3.6 7.1 4.4 4.8 Ductal/Lobular 2.6 6.2 4.3 3.6 Other 1.9 6.7 2.5 2.6 KI67 <20% 2.5 6.4 3.4 3.3 >=20% 2.3 5.5 3.5 3.7 Tumor Grade Well differentiated 1.9 5.8 2.4 2.6 Moderately differentiated 2.7 6.1 3.9 3.9 Poorly differentiated/undifferentiated 2.9 4.8 4.3 4.8 Node Positivity Positive 5.2 5.6 9.3 9.5 Negative 2.0 5.8 2.6 2.7

Acute myeloid leukemia (AML) is an aggressive hematologic malignancy characterized by the clonal proliferation of myeloid precursors and rapid progression. Historically consisting of intensive chemotherapy, AML management has evolved significantly due to advances in molecular diagnostics and risk stratification. This review discusses current therapeutic paradigms in AML, emphasizing the growing role of personalized medicine across age and risk groups. For younger, fit patients, intensive regimens such as the “7 + 3” protocol remain the standard, often enhanced by targeted agents like FMS-like tyrosine kinase 3 (FLT3) and IDH inhibitors. Older or unfit individuals benefit from low-intensity treatments such as hypomethylating agents combined with venetoclax, now considered a frontline standard of care. The use of liposomal chemotherapy (CPX-351), measurable residual disease (MRD) monitoring, and maintenance therapy further refine post-remission strategies. Emerging therapies, including menin inhibitors, antibody–drug conjugates, and immunotherapies like CAR-T cells and vaccines, offer additional options, especially in relapsed/refractory settings. This comprehensive review outlines the current landscape and future directions in AML therapy, emphasizing the transition toward individualized, mutation-driven treatment strategies.