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Background: The term classical hematology (CH), referring to a subspecialty focusing on non-cancer blood disorders, was officially adopted by the American Society of Hematology (ASH) in 2022. There is a perceived shortage of classical hematologists, although data are limited (Winter JN, Hematologist 2022). Prior studies have shown that <6% of hematology-oncology fellows pursue a practice subspecializing in CH after training (Todd RF, Blood 2004; Marshall Al, Blood Adv 2018). Moreover, mentorship is consistently cited as the most important factor guiding fellows' career decisions (Sharma D, Blood Adv 2019; Masselink LE, Blood Adv 2019). To help bridge the CH workforce gap, ASH has supported additional hematology-focused fellowship programs (HFFP) within select hematology-oncology fellowship programs. CH constitutes a large proportion of consults in US National Cancer Institute (NCI)-designated cancer centers (West CV, JCO Oncol Pract 2024). The goals of our study were: 1) to determine the proportion of adult hematologist-oncologists within NCI cancer centers who practice CH; and 2) to describe the physician characteristics of cancer centers with HFFP and compare these centers to those without HFFP. Methods: We included all NCI-designated cancer centers with a clinical program as of April 1, 2024. The only exception was St Jude Children's Hospital due to its pediatric focus. We obtained the practice profile of each internal medicine-trained adult hematologist-oncologist (henceforth, physician) as well as the availability of HFFP from the respective cancer center websites. We also searched the corresponding department of medicine and division of hematology at each affiliated academic institution to ensure inclusion of all physicians practicing CH. Each physician was classified into one of the following categories: classical hematologist (attending to only non-cancer conditions), general hematologist-oncologist (cancer and non-cancer conditions), and oncologist (cancer only). The number of hematology-oncology fellowship programs in the US was obtained from the Accreditation Council for Graduate Medical Education. Results: We included 64 NCI-designated cancer centers, 55 of which were considered as comprehensive cancer centers. There was a total of 4,616 physicians (3,891 oncologists [84.3%], 487 hematologists-oncologists [10.6%], and 238 classical hematologists [5.1%]). The median numbers of physicians, oncologists, general hematologist-oncologists, and classical hematologists per center were 55 (range, 16-275), 45 (range, 12-270), 5 (range, 0-48), and 3 (range, 0-13), respectively. The median proportions of classical hematologists and physicians practicing CH (general hematologist-oncologists plus classical hematologists) were 5.1% (range, 0-20.0) and 14.9% (range, 0-55.6%), respectively. There were 12 HFFP within NCI-designated cancer centers (18.8%). Most (11/12) centers with HFFP had >50 physicians (median 95 [range, 38-185]) and >5% classical hematologists (median 6% [range, 3.8-13.5%]); 11 centers with similar characteristics did not have HFFP. Centers with HFFP have significantly higher numbers of physicians (median 95.0 [range, 38-185] vs 49.5 [range, 16-275]; P=0.001) and classical hematologists (median 6.0 [range, 3-13] vs 2.0 [range, 0-11]; P<0.001) but similar proportions of classical hematologists (median 6.0% [range, 3.8-13.5] vs 4.5% [range, 0-20.0]; P=0.078) and physicians practicing CH (median 12.3% [range, 6.5-47.7] vs 15.7% [range, 0-55.6]; P=0.402) compared to those without HFFP. Conclusions: Among adult hematologist-oncologists at NCI-designated cancer centers, only 1 in 20 are classical hematologists, although 1 in 7 have CH as part of their practice. Within NCI-designated cancer centers, only 1 in 5 have an HFFP. These findings suggest that there is an opportunity for NCI-designated cancer centers to encourage and recruit physicians subspecializing in CH and a rationale to create additional HFFPs. These measures may help further alleviate CH workforce shortages and expand CH mentorship to meet the needs of an increasingly complex subspecialty within hematology.

Introduction Monoclonal antibodies (MoAbs) directed against CD38 are a mainstay in multiple myeloma (MM). Downregulation of CD38 expression is a resistance mechanism of antigenic escape, however, cell surface expression may return. While this tumor cell plasticity is likely driven by epigenetic mechanisms, it is unknown if MM cells can develop permanent resistance to anti-CD38 MoAb by acquiring genomic events leading to biallelic disruption of CD38 thus precluding re-treatment. Here, we report biallelic loss of CD38 as a recurrent mechanism of resistance, often via convergent evolution where distinct subclones are advantaged towards the same selective pressure. Methods We interrogated two sets of patients (Mayo Clinic; n = 31, Calgary University; n =19) with relapse following anti-CD38 MoAbs. Two additional cases of interest were selected from Heidelberg University. Whole genome sequencing (WGS, 60-100x) or whole exome sequencing (WXS), flow cytometry (flow), and bulk RNAseq were used to validate the effect of genomic events on CD38. Missense mutations predicted to affect CD38 MoAb binding were validated with site-directed mutagenesis of a CD38 plasmid, transduction into K562 MM cells, and CD38 MoAb binding assays. Results The prevalence of biallelic inactivation of CD38 at anti-CD38 MoAb relapse was 6% (3/50). An additional selected biallelic event was noted in the Heidelberg set. Each case is described in detail: MM-19 (Calgary) received daratumumab (Dara), lenalidomide, and dexamethasone (Dex), and then had a second exposure to Dara, following relapse. At this second relapse, WGS was performed on two independent extramedullary disease localizations in the liver. Both samples had unique, large deletions (>3 Mb) on chromosome 4 coupled with additional unique focal deletions involving CD38. Flow confirmed the presence of CD138+/CD38- plasma cell populations in both sites. A second case of convergent evolution was seen in a patient (Mayo) after seventh-line Dara/Len/Dex. WGS revealed a common deletion encompassing CD38. On the remaining allele, one subclone had a structural variation-mediated loss of CD38(cancer cell fraction; CCF 40%) while another harbored an L153H missense mutation (CCF 60%). Flow confirmed presence of two CD138+ clones; one with diminished CD38 expression. L153H was functionally validated to abrogate Dara binding, while maintaining CD38 expression. The third sample was collected after fifth-line Dara and sixth-line Dara/Bortezomib/Dex (Heidelberg) and represents another case of convergent evolution with a common loss of chromosome 4 and two subclones detected by WGS (P98Lfs*12, CCF 39% resulting in biallelic inactivation; R140G, CCF 61%). Bulk RNAseq revealed, in comparison to NDMM from CoMMpass, CD38 expression below the first decile. Notably, the R140G variant reduced binding affinity to Dara but not to Isatuximab (Isa). A fourth case (Mayo) relapsing after 6 months of Dara-based therapy similarly had a focal deletion of CD38 with an L18Sfs*16 frameshift deletion on the remaining allele associated with a 4.35-fold reduction in CD38 expression by RNAseq compared to pre-treatment. Interestingly, in 3/4 cases the CD38-negative clone emerged after a second exposure to anti-CD38 MoAb, suggesting emergence with the first exposure and then selection during the second. One other monoallelic event (C275Y; Heidelberg) was detected post-Isa. Copy number of the alternate allele is not known given targeted sequencing methodology, but the variant was seen to reduce binding affinity to both Dara and Isa. The prevalence of monoallelic loss of CD38 in newly diagnosed MM from MMRF CoMMpass was 7% (50/701) and two patients had mutations in CD38, but there were no cases of biallelic loss suggesting these events are driven by treatment pressure. Conclusion Distinction of the mode of CD38 loss is valuable for predicting outcome of re-challenge to anti-CD38 MoAbs. We see here an estimated 5-10% of anti-CD38 MoAb relapses are characterized by genomic antigen escape. Results here are in line with antigen escape to BCMA- and GPRC5D-directed immunotherapies (Lee et al, Nat Med 2023), suggesting that acquired antigen escape resulting from prolonged exposure to the selective pressures of immunotherapy is a recurrent mechanism of resistance in MM. Moreover, in select cases, non-overlapping resistance mutations provide rationale for switching agents at second exposure.

Introduction The pathogenic role of somatic non-coding (nc) single nucleotide variants (SNVs) is underexplored in multiple myeloma (MM) and additional characterization of these regions has the potential to provide significant new insights into disease progression. To investigate the role of ncSNVs and their relationship with MM pathogenesis, we have characterized a novel series of WGS from 294 cases of MGUS, SMM, and MM using computational tools optimized to identify functional driver SNVs in these regions. We hypothesize the ncSNVs that co-localize to sites of super-enhancers (SEs) active in plasma cells (PC) are sites of high functional impact SNVs and these mutations lead to the dysregulated expression of genes that should be silent at the terminally differentiated stage of PCs, providing a selective advantage that shapes the fitness of the MM genomic landscape. Methods We analyzed 294 high-coverage matched tumor/normal pairs (80x tumor and 40x normal) derived from 21 MGUS, 86 SMM, 167 NDMM and 40 RRMM. In addition to previously sequenced samples, newly sequenced patients were obtained from NYU Langone Health, Memorial Sloan Kettering Cancer Center, University of Alabama at Birmingham and University of Miami following IRB-approved informed consent. DNA was extracted from CD138+ purified bone marrow plasma cells using standard approaches. We used the MGP1000 (https://github.com/pblaney/mgp1000) to process sequencing data which employs a union-consensus mechanism for determining the final set of variants. We collected enhancer elements (E/SEs) active in GC B-cells, ABC-DLBCL and GBC-DLBCL (Bal, et al. Nature, 2022) and PC specific E/SEs (Loven, et al. Cell 2013). FunSeq2 was used to score ncSNVs. GRAM was used to predict how variants alter TF binding and gene expression in a subset of 6 cases with paired WGS in our series and will expand this analysis on a validation set of 263 NDMM and 93 RRMM cases from University-Hospital Heidelberg enrolled in the GMMG-HD6 clinical trial. Results We identified 1,952,232 high-quality SNVs with 18,199 (0.93%) accumulating in 280 focal sites we termed “mutationally enriched regions” or MERs. To discern SNVs in MERs with the highest potential for imparting a selective advantage, we clustered mutations based on the density of FunSeq2 impact scores which uses reference data contexts on sequence conservation, modification of transcription factor (TF) binding, and gene linkage to regulatory elements and network hubs from pan-cancer studies. We show that MERs are enriched for ncSNVs with high impact scores (mean=2.57) compared to random similarly-sized regions of the genome (Fisher's exact test P<9.7e-12, OR=10.10 [3.88-37.40]). The high impact ncSNVs (hi-ncSNVs) in MERs (n=220) account for 8.09% of all hi-ncSNVs and are present in 46.3% of cases (136/294) with some patients having up to 7. The proportion of cases carrying a MER hi-ncSNVs was similar across disease stages (MGUS=42.9%, SMM=46.5%, MM=40.7%, and RR=47.5%). Analysis of the VAF of MER hi-ncSNVs shows a minor shift towards more clonal versus subclonal mutations (53.6% vs 46.4% VAF>=0.25) suggesting some high impact mutations are acquired in the GC but additional hi-ncSNV are acquired later in PC development, providing evidence that hi-ncSNVs accumulate in MERs throughout disease progression. We mapped these hi-ncSNVs to associated genes then intersected the loci with E/SEs active in GCBs and PCs to determine their functional context. This approach identified 12 genes affected by hi-ncSNVs including the previously identified nc-drivers NEAT1, MIR142, ZCCHC7, and IGLL5 as well as the PC differentiation genes IRF8, BACH2, proliferation genes RHOH, SPRED2, known coding MM drivers CCND1, ZFP36L1, and chr1q genes BTG2 and CROCC. We predicted the effect of ncSNVs on expression through modulation of TF binding at this set of putative nc drivers in MM and identified a trend towards increase in expression of SPRED2, CCND1, NEAT1, and IGLL5 compared to non-mutated cases (P=0.089). We will present data on the validation of this set of genes on a larger set of data derived from the Heidelberg group. Conclusions We identified a set of 12 putative nc driver genes in MM that modify expression and have the potential to significantly alter the pathogenesis of MM by providing a selective survival advantage. We will present the impact of these by clinical stage and on outcome.

Introduction: Survival of children with relapsed/refractory (r/r) acute myeloid leukemia (AML), myelodysplastic syndromes (MDS) and juvenile myelomonocytic leukemia (JMML) remains dismal, and successful treatment approaches are limited. Myeloid leukemias frequently have high telomerase expression, and neoplastic progenitor cells have relatively shorter telomeres compared to normal tissues due to the balance between frequent malignant cell division and compensatory increased telomerase activity. In one study, the 5-year overall survival (OS) in children with AML and lower telomerase activity was 88% compared to 43% for those with higher activity, suggesting potential prognostic and therapeutic importance of telomerase in this population (Verstovsek Cancer 2003). Imetelstat is a first-in-class telomerase inhibitor approved by the FDA in 2024 for the treatment of adult patients with low-to-intermediate-1 risk myelodysplastic syndromes (LR-MDS) with transfusion-dependent anemia who are r/r/ineligible for erythropoiesis-stimulating agents. . Imetelstat has also been shown to drive AML cells into ferroptosis (Bruedigam Nature Cancer 2024). The Children's Oncology Group (COG) previously conducted the ADVL1112 Phase 1 study of imetelstat monotherapy in children with r/r solid tumors or lymphomas (Thompson CCR 2013). Imetelstat was administered intravenously on Days 1 and 8 of a 21-day cycle. The recommended phase 2 dose (RP2D) was 268 mg/m2. Imetelstat was well-tolerated with no grade >3 non-hematologic toxicities and one dose-limiting thrombocytopenia observed in a subject treated at the RP2D. In preclinical studies, imetelstat was active against leukemia stem cells in pediatric AML patient derived xenograft models (Barwe J Clin Med, 2022). Methods: PEPN2312 is an open-label, multi-center phase 1 study of imetelstat in combination with fludarabine/high dose cytarabine (FLA) for patients with AML in second or greater relapse, refractory to re-induction after first relapse, or r/r MDS or JMML (NCT06247787). The primary objective of this study is to estimate the maximum tolerated dose (MTD) and/or RP2D of imetelstat in combination with FLA in this patient population. Secondary objectives include toxicity assessment, pharmacokinetics, clinical response/minimal residual disease assessments per standard criteria, and OS. Exploratory analyses will be conducted to analyze telomerase activity in peripheral blood mononuclear cells, conduct pharmacodynamic studies, and evaluate any changes in cytogenetic and mutational abnormalities. Eligible patients must be between the ages of 1 to 18 at the time of study enrollment with Lansky/Karnofsky performance status of ≥50. Patients with leukemia must have platelet count >25,000/µL and hemoglobin >8 g/dL (transfusions allowed). Patients known to have a congenital bone marrow failure syndrome are excluded. This study will use the Rolling 6 design to estimate the MTD/RP2D. The starting dose of imetelstat (DL1) is 212 mg/m2 IV over 2 hours (80% of the single-agent RP2D) given on days 1 and 8 of a 28-day cycle in combination with FLA administered days 2-6. Premedication for infusion reactions with an antihistamine and corticosteroid are required prior to each dose of imetelstat. Patients may receive up to 2 cycles of therapy in the absence of progressive disease or unacceptable toxicity as graded by CTCAE version 5.0. Response assessment will be performed via morphology and central flow cytometry analysis for patients with AML and standard response criteria for patients with JMML or MDS (Niemeyer Haematologica 2015; Zeidan Blood 2023). One dose escalation to 268 mg/m2 (DL2) will be explored if DL1 is deemed safe. Intra-patient dose escalation is not permitted. Pharmacokinetic sampling will be performed during cycle 1. Once the MTD/RP2D is determined, further assessment of safety and preliminary activity of imetelstat and FLA chemotherapy will occur in an expansion cohort of up to 6 additional patients treated at the MTD/RP2D. PEPN2312 was activated in July 2024 and will enroll at 21 participating COG/PEP-CTN sites.

Background The American Society of Clinical Oncology (ASCO) launched the Diversity in Oncology initiative in 2017 to address the need for increased minority representation in the hematology-oncology workforce. A recent series of reports, titled “State of the Oncology Workforce in America,” published in JCO Oncology Practice in 2021 and 2022, focused on this issue. Notably, these reports did not include any data regarding the representation of Asian minorities in the field. Therefore, our objective was to assess the proportion of Asian professionals within the hematology-oncology workforce, encompassing both practitioners and trainees. Methods We conducted a comprehensive search for publicly available data regarding Asian representation among US hematology-oncology practitioners and trainees in both adult and pediatric fields. Our primary data sources included the 2020 US Census, the Association of American Medical Colleges, the Accreditation Council for Graduate Medical Education, and various professional societies. We defined practitioners to include hematologist-oncologists, gynecologic oncologists, radiation oncologists, surgical oncologists, hematopathologists, hematology-oncology nurse practitioners, hematology-oncology physician assistants, and nurses specializing in hematology-oncology. Trainees encompassed fellows and residents. Additionally, we gathered comparable data on the US population, medical students, adult internal medicine residents, gynecology residents, pediatric residents, pathology residents, surgery residents, nurses, nurse practitioners, and physician assistants. To provide a comprehensive overview of the hematology-oncology workforce, we utilized data from 2020 to 2022, and whenever possible, we collected longitudinal data on trainees over the years. Results As of 2020, Asians represented 6.2% of the US population. Among hematology-oncology physician practitioners, the percentage of Asian individuals ranges from 14.7% to 32.1%, including 32.1% of adult hematologist-oncologists, 20.4% of pediatric hematologist-oncologists, 25.9% of radiation oncologists, 14.7% of gynecologic oncologists, and 7.0% of hematology-oncology physician assistants. In the realm of physician trainees, Asian representation is between 17.9% and 35.3%, with 35.3% of adult hematology-oncology fellows, 20.0% of pediatric hematology-oncology fellows, 26.4% of radiation oncology residents, and 17.9% of gynecologic oncology fellows. Additionally, the proportion of Asian residents from which hematology-oncology fellows are drawn ranges from 14.9% to 35.9%. Specifically, 35.9% of internal medicine residents, 22.0% of pediatric residents, 14.9% of gynecology residents, 26.6% of pathology residents, and 19.2% of surgical residents are Asian. Furthermore, 26.7% of medical students identify as Asian. Notably, the proportions of Asian hematology-oncology trainees and medical students have remained relatively stable from 2005 to 2022. Data on hematopathologists, surgical oncologists, and non-physician practitioners are limited, although Asian representation among hematology-oncology physician assistants is 7.0% and among nurses is 7.2%. Conclusions Asians comprise a large segment of the hematology-oncology workforce in the US. While only 1 in 20 people in the US are Asians, between 1 in 3 and 1 in 5 hematology-oncology physician practitioners and trainees, are Asians. Data are limited for non-physician practitioners. Asian minority representation should be highlighted and considered as an example of success in diversity in hematology-oncology workforce. This framework should be embraced moving forward to continue advancing minority representation throughout the field of hematology-oncology.

Introduction: Over 80,000 new cases of Non-Hodgkin's Lymphoma (NHL) are diagnosed annually, but modifiable risk factors are largely unknown. Circadian disruption has been identified as a risk factor for several cancers, including breast and prostate cancer, and affects immune cells such as Natural Killer (NK) cells and T-helper cells. Disruptions in circadian rhythms can lead to aberrant immune cell trafficking and proliferation. Despite this biological connection, evidence linking circadian disruptions to NHL remains inconclusive. Only single Mendelian Randomization (MR) study (PMID: 32895918) has explored the causal relationship between sleep traits and overall NHL risk, without examining NHL subtypes. Studies have shown distinct risk factor profiles among NHL subtypes. Therefore, this study aims to investigate the causal relationship between sleep traits and NHL subtypes in European populations using MR. Methods: We conducted a two-sample MR analyses using genome-wide association studies (GWAS) summary data on sleep traits and NHL subtypes. The GWAS summary statistics on sleep traits were obtained from publicly available UKBiobank datasets. The sleep traits analyzed included chronotype (N=449,734), insomnia (N=237,627), sleep duration (N=446,118), daytime sleepiness (N=452,071), short sleep (N=411,934), and long sleep (N=339,926). Only independent, genome-wide significant SNPs (p < 5×10-8) were considered as valid instruments. The NHL subtype-specific summary statistics came from the InterLymph including follicular lymphoma (FL: N=6,508 cases / 64,183 controls), mantle cell lymphoma (MCL: N=1,169 cases / 61,603 controls), and Waldenström macroglobulinemia/lymphoplasmacytic lymphoma (WM/LPL: N=1,697 cases / 59,333 controls). Our primary analysis used the random-effects inverse-variance weighted (IVW) method. In addition, we employed MR-Egger to adjust for directional pleiotropy. Heterogeneity in the MR results was evaluated with Cochran's Q statistic. Results: The IVW method did not identify any statistically significant causal association between sleep traits and the risk of NHL subtypes (FL,MCL,WM/LPL), but did yield several intriguing associations. Chronotype (early rising) showed a tendency towards a marginally an increased NHL risk across subtypes [Odds ratio (OR) range: 1.07 - 2.56]. Conversely, a decreased risk was noted for long sleep (≥ 9 hours vs. 7-8 hours) [OR range: 0.19 - 0.62], insomnia [OR range: 0.72 - 0.88], and short sleep (excludes MCL) [OR range: 0.12 - 0.72]. Confidence limit for long sleep was wide due to small number of variants (N=8). The MR-Egger regression analysis did not provide evidence of significant directional horizontal pleiotropy. The F-statistics for all sleep traits were greater than 10 indicating absences of weak instrument bias. Conclusions: Our study found no statistically significant associations between sleep traits and three NHL subtypes (FL, MCL, WM/LPL) in European populations. However, we observed potential influences of chronotype, long and short sleep, and insomnia on NHL risk. These findings align with and extend previous MR study by providing subtype-specific insights. Future directions include expanding our analysis to additional NHL subtypes, generating polygenic risk scores, and conducting stratified analyses using the InterLymph population. These efforts aim to further elucidate the complex relationship between sleep characteristics and NHL risk across diverse subtypes and populations.

BACKGROUND While there has been improved gender representation in dermatology, there remains areas for improvement, especially in leadership positions. Studies have evaluated diversity in various dermatology subspecialties, but evaluation of gender diversity in cosmetic dermatology is lacking. OBJECTIVE To evaluate the temporal trends in gender diversity within the American Society for Dermatologic Surgery (ASDS) Cosmetic Dermatologic Surgery Fellowship Programs from 2013 to 2022. To discuss strategies for improvement. MATERIALS AND METHODS The ASDS Cosmetic Dermatologic Surgery Fellowship program directors and fellows were reviewed from 2013 to 2022. Gender was determined through online professional websites and biographies. The number and proportion of each gender was determined for each year, and the change over time was calculated. RESULTS The number of fellowship positions and program directors has increased from 2013 to 2022. Most of the fellows have been women. The average yearly rate of change for fellows is +1.67 and +0.67 for men and women. Most of the fellowship directors have been men. The average yearly rate of change is +1.56 and +0.44 for men and women. CONCLUSION Gender inequalities remain across leadership positions and further studies are necessary to better determine why these discrepancies exist and how to improve this inequality.

Abstract Glioblastoma (GBM) is an aggressive form of brain cancer with poor survival despite standard of care. Checkpoint inhibitors aimed to revive dysfunctional T cells have significantly improved outcomes in other cancers, but have failed GBM. GBM patients have severe peripheral immunosuppression, including severe lymphopenia, immune organ atrophy, and defective T cell responses. This immunosuppression is a critical barrier to patient survival and the success of immunotherapies. Using parabiosis, we demonstrated that serum-derived factors were sufficient to drive hallmark features of immunosuppression, including inhibition of ex vivo T cell proliferation. This factor was nonsteroidal in nature and had molecular weights greater than 100kDa. Mass-spectrometry and pathway analysis of the suppressive serum implicated proteins involved in DNA response elements, cell death, and DNA-histone complexes. We hypothesized that the factor is cell-free DNA (cfDNA). Confirming this, serum levels of cfDNA are increased in glioma-bearing mice. Moreover, exposure to cfDNA from serum of glioma-bearing mice was sufficient to directly and potently inhibit T cell proliferation ex vivo. Interestingly, exposure to genomic DNA was not sufficient to induce proliferation defects in T cells, highlighting the unique features of cfDNA. Importantly, reducing cfDNA content using DNaseI partially restored proliferation capacity. We determined that the T cell proliferation defects were independent of DNA sensing mechanisms through AIM2, implicating a novel pathway of DNA sensing in T cells. Finally, to determine the origin of the cfDNA, we employed methyl-seq. The chromatin signature most closely represented neutrophils. This highlights a potential role for neutrophils-derived cfDNA as a targetable strategy in GBM. Together, we contend that cfDNA induces immunosuppressive effects in GBM and devising strategies to reduce circulating cfDNA could be a therapeutic approach to improve T cell functions and outcomes in GBM patients.

PURPOSE The nodal burden of patients with residual isolated tumor cells (ITCs) in the sentinel lymph nodes (SLNs) after neoadjuvant chemotherapy (NAC) (ypN0i+) is unknown, and axillary management is not standardized. We investigated rates of additional positive lymph nodes (LNs) at axillary lymph node dissection (ALND) and oncologic outcomes in patients with ypN0i+ treated with and without ALND. METHODS The Oncoplastic Breast Consortium-05/ICARO cohort study (ClinicalTrials.gov identifier: NCT06464341 ) retrospectively analyzed data from patients with stage I to III breast cancer with ITCs in SLNs after NAC from 62 centers in 18 countries. The primary end point was the 3-year rate of any axillary recurrence. The rate of any invasive recurrence was the secondary end point. RESULTS In total, 583 patients were included, of whom 182 (31%) had completion ALND and 401 (69%) did not. The median age was 48 years. Most patients (74%) were clinically node-positive at diagnosis and 41% had hormone receptor–positive/human epidermal growth factor receptor 2–negative tumors. The mean number of SLNs with ITCs was 1.2. Patients treated with ALND were more likely to present with cN2/3 disease (17% v 7%, P < .001), have ITCs detected on frozen section (62% v 8%, P < .001), have lymphovascular invasion (38% v 24%, P < .001), and receive adjuvant chest wall (89% v 78%, P = .024) and nodal radiation (82% v 75%, P = .038). Additional positive nodes were found at ALND in 30% of patients, but only 5% had macrometastases. The 3-year rates of any axillary and any invasive recurrence were 2% (95% CI, 0.95 to 3.6) and 11% (95% CI, 8 to 14), respectively, with no statistical difference by type of axillary surgery. CONCLUSION The nodal burden in patients with ypN0(i+) was low, and axillary recurrence after ALND omission was rare in patients selected for this approach. These results do not support routine ALND in all patients with ypN0(i+).