Abstract Context Most of the patients included in the clinical trials and real-world studies with osilodrostat only include patients with adrenocorticotropic hormone dependent Cushing syndrome (CS), while data on the efficacy and safety of osilodrostat in patients with adrenal CS is scarce. Objective To assess the efficacy and safety of osilodrostat in adrenal CS. Methods International study of patients with adrenal CS: patients treated with osilodrostat at any time were enrolled in the safety evaluation and those treated for longer than 4 weeks, in the efficacy evaluation. Patients were classified as responders if they experienced a reduction in urinary free cortisol (UFC) >50% (complete responders when UFC levels were below the upper limit of normal [ULN] and partial responders if there was a reduction >50% but not normalization). Results Twenty-eight patients with adrenal CS were enrolled: 16 with adrenocortical carcinoma and 12 with benign disease. Osilodrostat was used in monotherapy in 22 patients and in combination with metyrapone in 6 cases. In those patients treated for longer than 4 weeks (n = 21), 66.7% were classified as responders (28.6% with complete response and 38.1% with partial response), and for those treated for longer than 12 weeks, the rate of response increased to 87.5% The use of osilodrostat as a nonfirst-line therapy (odds ratio 15.0, P = .010) was a predictor of response. Osilodrostat led to a significant decrease in systolic blood pressure and body weight (P < .05). Nine patients developed one or more adverse events and in 56% (n = 5) led to osilodrostat discontinuation. Conclusion Osilodrostat controls hypercortisolism in 66.7% of patients with adrenal CS treated for longer than 4 weeks and in 87.5% of cases treated for longer than 12 weeks, with a positive impact on blood pressure and body weight. Patients who received osilodrostat after other previous steroidogenesis inhibitors have a higher probability of response.
Herbert Mayo (1796–1852): a pioneering neuroanatomist’s forgotten legacy
British anatomical physiology in the early 19th century evolved from the work of William Harvey, Thomas Willis, and William Hunter, who emphasized cerebral functional localization, integrating physiology and anatomy. This novel perspective was championed by Herbert Mayo (1796–1852). A student of Charles Bell at the Middlesex Hospital in London, Mayo subsequently became a surgeon there in 1818 and later a professor of anatomy and surgery. His experiments on the motor functions of the seventh cranial nerve and sensorimotor functions of the fifth cranial nerve brought him renown. Mayo, inspired by Johann Christian Reil, also conducted the first accurate brainstem dissections, developed innovative tissue preservation methods, and provided detailed descriptions of key fiber tracts. Mayo’s 1822–1823 Anatomical and Physiological Commentaries and 1827 A Series of Engravings Intended to Illustrate the Structure of the Brain and Spinal Chord in Man accurately depicted the corona radiata, cerebellar peduncles, and uncinate fascicle. In his 1842 book, The Nervous System and Its Functions , Mayo discussed the localization of higher brain functions. His dissections remained unmatched until Josef Klingler’s work in 1934. Despite the quality of his work, Mayo has been largely neglected, possibly because of his tumultuous relationship with Bell and later professional difficulties. Nevertheless, Mayo significantly contributed to white matter anatomy and led the search for cerebral localization, subsequently impacting neurosurgery. This article examines his life and work.
Biparametric vs Multiparametric MRI for Prostate Cancer Diagnosis
Importance Multiparametric magnetic resonance imaging (MRI), with or without prostate biopsy, has become the standard of care for diagnosing clinically significant prostate cancer. Resource capacity limits widespread adoption. Biparametric MRI, which omits the gadolinium contrast sequence, is a shorter and cheaper alternative offering time-saving capacity gains for health systems globally. Objective To assess whether biparametric MRI is noninferior to multiparametric MRI for diagnosis of clinically significant prostate cancer. Design, Setting, and Participants A prospective, multicenter, within-patient, noninferiority trial of biopsy-naive men from 22 centers (12 countries) with clinical suspicion of prostate cancer (elevated prostate-specific antigen [PSA] level and/or abnormal digital rectal examination findings) from April 2022 to September 2023, with the last follow-up conducted on December 3, 2024. Interventions Participants underwent multiparametric MRI, comprising T2-weighted, diffusion-weighted, and dynamic contrast–enhanced (DCE) sequences. Radiologists reported abbreviated biparametric MRI first (T2-weighted and diffusion-weighted), blinded to the DCE sequence. After unblinding, radiologists reported the full multiparametric MRI. Patients underwent a targeted biopsy with or without systematic biopsy if either biparametric MRI or multiparametric MRI was suggestive of clinically significant prostate cancer. Main outcomes and measures The primary outcome was the proportion of men with clinically significant prostate cancer. Secondary outcomes included the proportion of men with clinically insignificant cancer. The noninferiority margin was 5%. Results Of 555 men recruited, 490 were included for primary outcome analysis. Median age was 65 (IQR, 59-70) years and median PSA level was 5.6 (IQR, 4.4-8.0) ng/mL. The proportion of patients with abnormal digital rectal examination findings was 12.7%. Biparametric MRI was noninferior to multiparametric MRI, detecting clinically significant prostate cancer in 143 of 490 men (29.2%), compared with 145 of 490 men (29.6%) (difference, −0.4 [95% CI, −1.2 to 0.4] percentage points; P = .50). Biparametric MRI detected clinically insignificant cancer in 45 of 490 men (9.2%), compared with 47 of 490 men (9.6%) with the use of multiparametric MRI (difference, −0.4 [95% CI, −1.2 to 0.4] percentage points). Central quality control demonstrated that 99% of scans were of adequate diagnostic quality. Conclusion and relevance In men with suspected prostate cancer, provided image quality is adequate, an abbreviated biparametric MRI scan, with or without targeted biopsy, could become the new standard of care for prostate cancer diagnosis. With approximately 4 million prostate MRIs performed globally annually, adopting biparametric MRI could substantially increase scanner throughput and reduce costs worldwide. Trial registration ClinicalTrials.gov Identifier: NCT04571840
Multiplex Spatial Proteomic Analysis of HER2–Positive Breast Tumors Reveals Unique Molecular and Immunologic Features Associated With Treatment Response
PURPOSE Predictive biomarkers to better tailor therapy for patients with early-stage human epidermal growth factor 2 (HER2)-positive breast cancer are a priority. We hypothesized that HER2 and immune-based biomarkers would be predictive of pathologic complete response (pCR) to preoperative trastuzumab/pertuzumab (HP). MATERIALS AND METHODS Patients with stage II/III, estrogen receptor (ER)-negative, HER2-positive breast cancer received neoadjuvant HP in the TBCRC026 clinical trial. The pCR after receiving HP alone was 22% (18/83). Tumor biopsies were performed at baseline. Secondary correlative objectives were to determine the relationship between HER2-based biomarkers and immune processes with pCR. NanoString code sets BC360 and IO360 were used to compare differential gene expression in baseline tumors that underwent pCR versus no pCR. NanoString GeoMx digital spatial profiling was used to assess immune protein abundance in intraepithelial and stromal segments. Stromal tumor-infiltrating lymphocytes and Ki67 were evaluated by hematoxylin and eosin and immunohistochemistry, respectively. RESULTS Intraepithelial HER2 protein abundance was significantly associated with pCR ( P = .001). Low HER2 abundance tumors were primarily basal-like, and essentially all (19/20) failed to achieve pCR. High HER2 abundance tumors that achieved pCR (14/51) exhibited a high degree of immune cell activity, whereas high HER2 abundance tumors that failed to achieve pCR tumors (37/51) were enriched for M-phase processes and epidermal growth factor receptor signaling. Baseline Ki67 was significantly higher in nonresponders ( P = .04). CONCLUSION ER-negative, HER2-positive breast cancer has unique molecular and immunologic features that may predict pCR after neoadjuvant HP. Validation of these potential biomarkers and composite biomarker analyses may guide design of future clinical trials.
Selective Elimination of Breast Surgery for Invasive Breast Cancer
Importance Neoadjuvant systemic therapy (NST) has been associated with pathologic complete response (pCR) in up to 60% of breast cancers (BCs). The findings of this trial question the necessity of surgery. Objective To report preplanned 5-year efficacy outcomes evaluating radiotherapy alone without breast surgery in patients selected with image-guided vacuum assisted biopsy (VAB). Design, Setting, and Participants This single-arm, prospective, phase 2 nonrandomized clinical trial was conducted at 7 US medical centers and included women 40 years or older with cT1-2N0-1M0 ERBB2 -positive (formerly HER2 -positive) or triple-negative invasive BC who showed residual breast lesions after NST of less than 2 cm on imaging. Enrollment was from March 6, 2017, to November 9, 2021. Data analysis was from October to December 2024. Intervention Image-guided VAB of the tumor bed (9G with a minimum of 12 cores) was performed after standard NST. Patients with clinically node-negative disease at diagnosis and no residual cancer in the breast on post-NST VAB underwent whole-breast radiotherapy with a boost without breast or axillary surgery. Patients with initial documented nodal disease and a breast pCR on VAB underwent targeted axillary dissection, while those with residual cancer when undergoing VAB had standard breast and axillary surgery. Patients were monitored with physical examinations and mammography every 6 months. Main Outcome Measures The primary outcome was ipsilateral breast tumor recurrence. Results Fifty patients (median [IQR] age, 62 [55-77] years) were enrolled and underwent post-NST VAB. Twenty-nine (58%) and 21 (42%) patients had ERBB2 -positive and triple-negative invasive BC, respectively. Breast pCR on VAB was identified in 31 patients (62%; 95% CI, 47.2%-75.34%), and axillary pCR was identified among all 8 patients with initial nodal metastases and breast pCR on VAB who underwent targeted axillary dissection. At a median follow-up of 55.4 (IQR, 44.0-63.5) months, the ipsilateral breast tumor recurrence rate was 0%, and disease-free and overall survival rates were 100% for patients without breast surgery. Conclusions and Relevance The results of this nonrandomized clinical trial that reported preplanned 5-year outcomes suggest that omission of breast surgery in select patients after NST may be feasible, with no recurrences seen. More confirmatory studies are necessary before this new approach alters surgical practice. Trial Registration ClinicalTrials.gov Identifier: NCT02945579
A phase 1 study of the CDK9 inhibitor voruciclib in relapsed/refractory acute myeloid leukemia and B-cell malignancies
Abstract The antiapoptotic protein, myeloid cell leukemia-1 (Mcl-1), contributes to the pathophysiology of acute myeloid leukemia (AML) and certain B-cell malignancies. Tumor dependence on Mcl-1 is associated with resistance to venetoclax. Voruciclib, an oral cyclin-dependent kinase (CDK) inhibitor targeting CDK9, indirectly decreases Mcl-1 protein expression and synergizes with venetoclax in preclinical models. This dose escalation study evaluated voruciclib in patients with previously treated hematologic malignancies. Initially, voruciclib was administered daily, continuously, on a 28-day cycle (group 1). After 2 patients with prior allogeneic stem cell transplantation had a dose-limiting toxicity (DLT) of interstitial pneumonitis at 100 mg, voruciclib administration was changed to days 1 to 14 of a 28-day cycle (group 2). Forty patients, 21 with AML and 19 with B-cell malignancies, were enrolled. Patients had a median of 3 prior lines of therapy (range, 1-8). Dose escalation in group 2 was stopped at 200 mg, a dose that achieved plasma concentrations sufficient for target inhibition, without DLTs observed. The most common adverse events were diarrhea (30%), nausea (25%), anemia (22%), fatigue (22%), constipation (17%), dizziness (15%), and dyspnea (15%). In AML, 1 patient achieved a morphologic leukemia-free state, and 2 had stable disease. Voruciclib treatment led to a decrease in MCL1 messenger RNA expression, downregulation of myelocytomatosis (MYC) and NF-κB transcriptional gene sets, and reduced phosphorylation of RNA polymerase 2. Voruciclib on intermittent dosing was well tolerated, with no DLTs, paving the way for evaluation of the combination of voruciclib with venetoclax for patients with previously treated AML. This trial was registered at www.clinicaltrials.gov as #NCT03547115.
Pembrolizumab in Children, Adolescents, and Young Adults with High-Risk Classic Hodgkin Lymphoma (cHL) with Slow Early Response to Front-Line Chemotherapy: Updated Results from the Phase 2 Keynote-667 Study
Background: Overall survival rates now exceed 90% for children, adolescents, and young adults with cHL, but patients with slow early response (SER) to front-line chemotherapy are at an increased risk of relapse. The approaches used historically to treat patients with SER included dose intensification and radiotherapy (RT), which can be associated with long-term toxicity. The open-label, phase 2 KEYNOTE-667study (NCT03407144) is designed to evaluate the efficacy and safety of consolidation with pembrolizumab plus chemotherapy with or without RT followed by pembrolizumab maintenance in patients with cHL and SER to front-line chemotherapy. The study includes 2 groups: patients with low-risk cHL (stage IA, IB, or IIA without bulky disease) and patients with high-risk cHL (stage IIEB-IVB). Prior analysis of the high-risk group showed that consolidation with pembrolizumab plus cyclophosphamide, vincristine, prednisone/prednisolone, and dacarbazine (COPDAC-28) followed by pembrolizumab maintenance had manageable safety and promising activity in patients with high-risk cHL and SER to front-line vincristine, etoposide, prednisone/prednisolone, and doxorubicin (OEPA). Here, we present updated results for patients with high-risk cHL and SER to OEPA. Methods: Patients eligible for the high-risk group were aged 3-25 years and had newly diagnosed stage IIEB, IIIEA, IIIEB, IIIB, IVA, or IVB cHL; measurable disease; and a Lansky Play-Performance Scale (aged <16 years) or a Karnofsky Performance Status (aged ≥16 years) score of ≥50. All patients in the high-risk group received 2 cycles of OEPA followed by early response assessment (PET and CT/MRI). Patients with a rapid early response (ie, Deauville score [DS] 1-3) received nonstudy therapy. Patients with a SER (ie, DS 4 or 5) received consolidation therapy with pembrolizumab 2 mg/kg up to 200 mg (aged 3-17 years) or 200 mg (aged 18-25 years) IV Q3W plus COPDAC-28 for 4 cycles. Patients then underwent late-response assessment (LRA; PET and CT/MRI). Patients with PET-positive disease at LRA (ie, DS 4 or 5) received RT (28.8 Gy) to late PET-positive residua. Patients with PET-negative disease (ie, DS 1-3) received no RT. All patients received maintenance pembrolizumab for up to 17 cycles. The primary end point was objective response rate (ORR) by blinded independent central review (BICR) per Cheson 2007 IWG criteria. Secondary end points included the rate of PET negativity after consolidation and safety. Results: 84 patients with high-risk cHL and SER to front-line OEPA received consolidation with pembrolizumab plus COPDAC-28. Median time from treatment allocation to data cutoff (Feb 29, 2024) was 24.3 months (range, 5.7-48.4). As of the data cutoff, 55 patients had completed consolidation and maintenance therapy, 20 were ongoing, and 9 had discontinued treatment (due to adverse events [AE], n = 3; progressive disease, n = 2; withdrawal by patient, n = 2; complete response [CR], n = 1; physician decision, n = 1). Patients received a median of 17 doses of pembrolizumab (range, 2-17) and the median time on pembrolizumab was 11.1 months (range, 0.5-11.8). The median age of patients was 14 years (range, 4-22), 78 (93%) were aged 3-17 years, 45 (54%) were male, 44 (52%) had bulky disease, and 53 (63%) had Ann Arbor stage IV disease. Of 84 patients who received consolidation, 80 (95%) had an LRA. The ORR among these patients was 99% (95% CI, 93-100; 57 CR and 22 partial response). 56 patients (70%) with a LRA were PET negative by BICR; 55 (69%) were PET negative by investigator review and did not receive RT. Treatment-related AEs were reported in 61 patients (73%); grade 3 or 4 treatment-related AEs occurred in 16 patients (19%). Three patients (4%) discontinued treatment due to treatment-related AEs. No patients died due to treatment-related AEs. Immune-mediated AEs occurred in 10 patients (12%). Conclusion: After additional follow up, consolidation with pembrolizumab plus COPDAC-28 with or without RT followed by pembrolizumab maintenance continued to demonstrate promising activity and manageable safety in patients with high-risk cHL and SER to front-line OEPA. Among the 80 patients with an LRA, 70% were PET negative by BICR and 69% were PET negative by investigator review and were spared RT. These results continue to support pembrolizumab plus COPDAC-28 consolidation as a treatment option that may augment response in patients with high-risk CHL and SER to front-line OEPA.
A Phase 1 Study of the Oral CDK9 Inhibitor Voruciclib in Combination with Venetoclax in Relapsed/Refractory (R/R) Acute Myeloid Leukemia (AML)
Background: Venetoclax in combination with hypomethylating agents (HMA) or low dose cytarabine is the standard of care for patients (pts) with newly diagnosed AML ineligible for intensive chemotherapy. However, responses are transient, and loss of response is associated with poor outcome. The antiapoptotic protein Mcl-1 promotes cell survival in AML and its overexpression is associated with resistance to venetoclax. Voruciclib, a potent oral CDK9 inhibitor (CDK9i), indirectly decreases Mcl-1 protein expression, and has synergistic activity with venetoclax in AML preclinical models. In the initial part of this study in 40 pts with R/R AML and B-cell malignancies, voruciclib at doses up to 200 mg administered on days 1-14 in a 28-day cycle was well tolerated, had no dose limiting toxicities (DLTs), and showed biologic and clinical activity in heavily pretreated pts (Blood 2023:142; Supp 1:4286). We hypothesized that voruciclib in combination with venetoclax may achieve greater antileukemic effect. Methods: Pts with R/R AML were eligible if aged ≥18 years, ECOG performance status ≤1, adequate organ function, and no prior CDK9i therapy. Dose escalation followed a 3+3 design, and DLTs were assessed in Cycle 1. Voruciclib was administered at 7 dose levels between 50 mg and 300 mg on days 1-14 of 28-day cycles. Venetoclax was administered at 200 mg on days 1-21 and 400 mg on days 22-28. Disease response was assessed by the 2017 ELN criteria. Mcl-1 protein expression and phosphorylation of RNA Pol IISer2 were evaluated in PBMC in cycle 1. The study is registered at clinicaltrials.gov (NCT03547115). Results: Enrollment in this portion of the study is complete with 41 pts. Median age was 67 years (range 34-89). Median number of prior lines of therapy was 2 (range 1-7), with 93% of pts having received venetoclax and HMAs, 51% having received an anthracycline, and 20% having had prior allogeneic hematopoietic stem cell transplant (HSCT). 2017 ELN risk was adverse in 73% of pts and intermediate in 17%. The median duration on therapy was 1.5 months (range 0.2 to 9+). No DLTs were observed, and based on PK/PD analysis, dose escalation was stopped at 300 mg without reaching the maximum tolerated dose. The most common adverse events (all grades/grade ≥3) were nausea (32%/0%), febrile neutropenia (27%/24%), dyspnea (22%/2%) diarrhea (22%/2%), hypokalemia (22%/5%) and thrombocytopenia (22%/20%). Seven pts died during treatment, 5 due to an infection and 2 due to hemorrhagic events. Anti-leukemic activity was observed in 10 (31%) of 32 pts treated with voruciclib at doses from 100-300 mg; 2 pts had CRi (one referred to HSCT and one with 6 months of remission prior to progression), 1 pt had MLFS (ongoing at 9 months), and 7 pts had stable disease lasting ≥3 months. Among 25 pts with circulating peripheral blood blasts, 18 (75%) showed a significant reduction of circulating blasts by day 14 of the first cycle; however, circulating blasts increased again in 8 of 18 pts during single agent venetoclax administration on days 15 to 28. Voruciclib pharmacokinetics (PK) was dose proportional. At 300 mg steady state, mean AUC0-24 was 21,526 ng x hr/mL and mean Ctrough was 644 ng/mL, exceeding concentrations needed for target inhibition in preclinical models. Voruciclib did not affect venetoclax PK. Pharmacodynamic studies including Mcl-1 protein expression and RNA Pol IISer2 phosphorylation in PBMC by flow cytometry showed on target effects and is reported separately. Conclusion: The combination of voruciclib with venetoclax is well-tolerated and has activity in pts with AML and disease progression after venetoclax. Because of the rebound in peripheral blasts after 14 days off voruciclib, voruciclib administered on days 1-21 per cycle merits further evaluation.
Adjuvant Trastuzumab Emtansine Versus Paclitaxel Plus Trastuzumab for Stage I Human Epidermal Growth Factor Receptor 2–Positive Breast Cancer: 5-Year Results and Correlative Analyses From ATEMPT
PURPOSE Long-term outcomes of patients with stage I human epidermal growth factor receptor 2 (HER2)–positive breast cancer receiving adjuvant trastuzumab emtansine (T-DM1) remain undefined, and prognostic predictors represent an unmet need. METHODS In the ATEMPT phase II trial, patients with stage I centrally confirmed HER2-positive breast cancer were randomly assigned 3:1 to adjuvant T-DM1 for 1 year or paclitaxel plus trastuzumab (TH). Coprimary objectives were to compare the incidence of clinically relevant toxicities between arms and to evaluate invasive disease-free survival (iDFS) with T-DM1. Correlative analyses included the HER2DX genomic tool, multiomic evaluations of HER2 heterogeneity, and predictors of thrombocytopenia. RESULTS After a median follow-up of 5.8 years, 11 iDFS events were observed in the T-DM1 arm, consistent with a 5-year iDFS of 97.0% (95% CI, 95.2 to 98.7). At 5 years, the recurrence-free interval (RFI) was 98.3% (95% CI, 97.0 to 99.7), the overall survival was 97.8% (95% CI, 96.3 to 99.3), and the breast cancer-specific survival was 99.4% (95% CI, 98.6 to 100). Comparable iDFS was observed with T-DM1 irrespective of tumor size, hormone receptor status, centrally determined HER2 immunohistochemical score, and receipt of T-DM1 for more or less than 6 months. Although ATEMPT was not powered for this end point, the 5-year iDFS in the TH arm was 91.1%. Among patients with sufficient tissue for HER2DX testing (n = 187), 5-year outcomes significantly differed according to HER2DX risk score, with better RFI (98.1% v 81.8%, hazard ratio [HR], 0.10, P = .01) and iDFS (96.3% v 81.8%, HR, 0.20, P = .047) among patients with HER2DX low-risk versus high-risk tumors, respectively. CONCLUSION Adjuvant T-DM1 for 1 year leads to outstanding long-term outcomes for patients with stage I HER2-positive breast cancer. A high HER2DX risk score predicted a higher risk of recurrence in ATEMPT.
RNA-Seq based gene expression profiling of baseline and on-treatment breast tumors to predict response to HER2-directed therapy, without chemotherapy (TBCRC026).
530 Background: Robust biomarkers are needed to personalize treatment in early stage HER2-positive breast cancer. The TBCRC026 trial (n=83) demonstrated that early metabolic changes on FDG-PET/CT [>40% decline in SULmax at day 15 post treatment initiation (C1D15); C1D15 SULmax] were associated with response to neoadjuvant trastuzumab/pertuzumab (HP), without chemotherapy, in an ER-negative, HER2-positive cohort (NCT01937117). We investigated the association of RNA sequencing (RNAseq)-based gene expression signatures (GES) at baseline and on-treatment (C1D15), with early metabolic change on PET/CT and clinical outcomes. Methods: RNAseq (664 GES) was performed on baseline (n=56) and C1D15 (n=31) tumor biopsies (25 paired samples available). Association with pCR following HP (secondary), PET/CT parameters and survival (exploratory) was studied. Gene expression changes between baseline and C1D15 samples were tested by Wilcoxon signed-rank test. Association between GES and PET/CT parameters and GES with pCR were evaluated using logistic regression models. Cox regressions were performed to study the association between PET/CT SULmax at C1D15 and a B cell signature and relapse-free survival (RFS). The likelihood ratio test was used to compare the prognostic ability of two nested Cox models. Results: Both RNAseq and clinical outcomes were available in 53/83 patients. HER2-enriched (HER2-E) intrinsic subtype comprised 71% (40/56) of cases at baseline and 61% (19/31) at D15; basal subtype for 27% (15/56) and 39% (12/31), respectively. pCR rate was 19% (10/53) with all but one exhibiting HER2-E subtype. One basal-like sample underwent pCR, with downregulation of HER2 amplicon and IgG signatures slightly more prominent. Gene expression changes from baseline to C1D15 were analyzed; ERBB2was downregulated after HP (p = 0.007), B cell signatures, CD4, CD8, natural killer cells and Treg cells were significantly upregulated at C1D15. GES associated with 40% decline in SULmax at C1D15 included ERBB2 amplicon genes ( ERBB2, GRB7) and correlation to the HER2-E subtype, whereas basal-like signatures were significantly associated with lack of response on PET at C1D15. Univariate logistic regression analysis suggested that FOS-JUN, fibroblast and B cell GES at baseline were significantly associated with pCR (p=<0.05). Finally, the addition of a B cell signature improved the prognostic value of C1D15 SULmax on PET/CT for RFS (p < 0.05). Conclusions: In this unique cohort with ER-negative, HER2-positive breast cancer treated with neoadjuvant HP without chemotherapy, HER2-E tumors and those with increased immune signaling were more likely to respond to HER2-directed therapy. Combining C1D15 SULmax on PET/CT and a B cell signature provided improved prognostic information and should be further explored as candidate biomarkers in this setting. Clinical trial information: NCT01937117 .