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Background: The anti-apoptotic protein Mcl-1 contributes to the pathophysiology of certain B-cell malignancies and AML, and dependence on Mcl-1 is associated with resistance to venetoclax. Efforts to target Mcl-1 through direct inhibition have faced challenges due to cardiovascular toxicities. Voruciclib, a potent oral CDK9 inhibitor (CDK9i), was shown to indirectly downregulate Mcl-1 protein levels and synergize with venetoclax in preclinical models in lymphoid and myeloid malignancies. In solid tumors, voruciclib maximum tolerated dose (MTD) was defined as 350 mg with continuous daily dosing, and 600 mg when used on days 1-14 on a 21-day cycle. This phase 1 study is the first to evaluate the safety, dose-limiting toxicities (DLT), preliminary efficacy, pharmacokinetics, and pharmacodynamics of voruciclib in R/R hematologic malignancies (NCT03547115). Methods: Patients (pts) with relapsed B-cell NHL, CLL, or AML aged ≥18 years who had ECOG performance status ≤1, disease progression after standard therapies, adequate hepatic and renal function, and no prior CDK9i were eligible. The study followed a 3+3 design and DLTs were assessed in Cycle 1. Voruciclib was administered daily continuously at a starting dose of 50 mg on a 28-day cycle (Cohort I). After 2 DLTs were observed at 100 mg in AML pts, dosing was changed to daily on days 1-14 on a 28-day cycle (Cohort II). Also, pts with prior allogeneic transplant were excluded and dose escalation (100, 150, 200 mg) proceeded separately in AML and B-cell malignancies. Disease response was assessed by investigators using the Lugano, 2008 iwCLL, and 2017 ELN criteria. Results: 40 pts were enrolled: 21 AML, 19 NHL (9 DLBCL, 3 CLL, 3 MCL, 3 FL and 1 MZL). Cohort I enrolled 16 pts, 8 each at 50 mg and 100 mg. Cohort II enrolled 24 pts (17 AML and 7 B-cell malignancies), including 6 at 100 mg, 7 at 150 mg, and 11 at 200 mg. Dose escalation in Cohort II did not reach the MTD and was stopped at 200 mg, a dose that achieved plasma concentrations sufficient for target inhibition. Median age was 70 years (range 40-90), 72.5% of pts were ≥65 years, and 77.5% had ECOG performance status = 1. Pts had a median of 3 prior therapies (range, 1-8). Median duration on drug was 5 weeks (range 1-22). Drug-related serious adverse events (AEs) were reported in Cohort I only. Two pts with AML had a DLT of Grade (Gr) 3 interstitial pneumonitis at 100 mg; both had had allogeneic transplant and active graft versus host disease, one of whom also had a concurrent Gr 3 differentiation syndrome. One pt with DLBCL at 50 mg had Gr 3 hypoxemic respiratory failure in Cycle 4. In Cohort II, no DLTs were observed and there were no non-hematologic Gr 3-5 drug-related AEs. In the overall population, the most common AEs were diarrhea (30%), nausea (25%), anemia (22.5%), fatigue (22.5%), constipation (17.5%), dizziness (15%) and dyspnea (15%) [Table 1). One pt with AML had Gr 3 hyperbilirubinemia. There was no evidence of drug-related neutropenia in pts with NHL. No significant cardiovascular AEs were observed. One pt with AML in Cohort I achieved a morphologic leukemia-free state. At 200 mg, 5 of 10 AML pts (50%) had stable disease. Voruciclib pharmacokinetics was dose proportional, mean accumulation ratio was 2.4, mean T max was 4 hours, and at 200 mg, steady state C max was 925 ng/mL and mean C trough was 442 ng/mL (~1 microM). Analysis of Mcl-1 protein expression in normal lymphocytes by flow cytometry showed a trend of decrease in on-treatment samples compared to pre-treatment. Consistent with this, RNA-Seq analysis of 3 paired CLL samples confirmed rapid (after 6 hours) downregulation of Mcl-1 mRNA transcript in the malignant B-cells. Furthermore, scRNA-Seq analysis of 2 longitudinal AML samples demonstrated downregulation of MYC transcriptional program and oxidative phosphorylation in circulating AML blasts, both evident 24 hours after start of voruciclib and ongoing at C1D15. Conclusions: Voruciclib at doses up to 200 mg administered on 14 consecutive days on a 28-day cycle was well tolerated, with no DLTs observed, and no cardiovascular toxicities. There was no significant myelosuppression in pts with B-cell malignancies. As the safety profile suggested non-overlapping toxicities with venetoclax, the study is now evaluating voruciclib in combination with venetoclax in pts with R/R AML to exploit dual inhibition of Bcl-2 and Mcl-1.

ImportancePatients should have an active role in decisions about pursuing or forgoing specific therapies in treatment de-escalation trials.ObjectiveTo evaluate longitudinal patient-reported outcomes (PROs) encompassing decisional comfort and health-related quality of life (HRQOL) among patients who elected to enroll in a clinical trial evaluating radiotherapy alone, without breast surgery, for invasive breast cancers with exceptional response to neoadjuvant systemic therapy (NST).Design, Setting, and ParticipantsProspective, single-group, phase 2 clinical trial at 7 US medical centers. Women aged 40 years or older with invasive cT1-2 N0-1 M0 triple-negative or human epidermal growth factor receptor 2 (ERBB2)–positive breast cancer with no pathologic evidence of residual disease following standard NST enrolled from March 6, 2017, to November 9, 2021. Validated PRO measures were administered at baseline and 6, 12, and 36 months post-radiotherapy. Data were analyzed from January to February 2023.InterventionsPRO measures included the Decision Regret Scale (DRS), Functional Assessment of Cancer Therapy—Lymphedema (FACT-B+4), and Breast Cancer Treatment Outcomes Scale (BCTOS).Main Outcomes and MeasuresChanges in PRO measure scores and subscores over time.ResultsAmong 31 patients, the median (IQR) age was 61 (56-66) years, 26 (84%) were White, and 26 (84%) were non-Hispanic. A total of 15 (48%) had triple-negative disease and 16 (52%) had ERBB2-positive disease. Decisional comfort was high at baseline (median [IQR] DRS score 10 [0-25] on a 0-100 scale, with higher scores indicating higher decisional regret) and significantly increased over time (median [IQR] DRS score at 36 months, 0 [0-20]; P < .001). HRQOL was relatively high at baseline (median [IQR] FACT-B composite score 121 [111-134] on a 0-148 scale, with higher scores indicating higher HRQOL) and significantly increased over time (median [IQR] FACT-B score at 36 months, 128 [116-137]; P = .04). Perceived differences between the affected breast and contralateral breast were minimal at baseline (median [IQR] BCTOS score 1.05 [1.00-1.23] on a 1-4 scale, with higher scores indicating greater differences) and increased significantly over time (median [IQR] BCTOS score at 36 months, 1.36 [1.18-1.64]; P < .001). At 36 months postradiotherapy, the cosmetic subscore was 0.45 points higher than baseline (95% CI, 0.16-0.74; P = .001), whereas function, pain, and edema subscores were not significantly different than baseline.Conclusions and RelevanceIn this nonrandomized phase 2 clinical trial, analysis of PROs demonstrated an overall positive experience for trial participants, with longitudinal improvements in decisional comfort and overall HRQOL over time and minimal lasting adverse effects of therapy.Trial RegistrationClinicalTrials.gov Identifier: NCT02945579

Across multiancestry groups, we analyzed Human Leukocyte Antigen (HLA) associations in over 176,000 individuals with Parkinson’s disease (PD) and Alzheimer’s disease (AD) versus controls. We demonstrate that the two diseases share the same protective association at the HLA locus. HLA-specific fine-mapping showed that hierarchical protective effects of HLA-DRB1 *04 subtypes best accounted for the association, strongest with HLA-DRB1 *04:04 and HLA-DRB1 *04:07, and intermediary with HLA-DRB1 *04:01 and HLA-DRB1 *04:03. The same signal was associated with decreased neurofibrillary tangles in postmortem brains and was associated with reduced tau levels in cerebrospinal fluid and to a lower extent with increased Aβ42. Protective HLA-DRB1 *04 subtypes strongly bound the aggregation-prone tau PHF6 sequence, however only when acetylated at a lysine (K311), a common posttranslational modification central to tau aggregation. An HLA-DRB1 *04-mediated adaptive immune response decreases PD and AD risks, potentially by acting against tau, offering the possibility of therapeutic avenues.

Abstract Background: The ATEMPT trial primary analysis found that one year of adjuvant trastuzumab emtansine (T-DM1) achieved a 3-year iDFS of 97.8% for patients with stage I HER2+ breast cancer, but was not associated with fewer clinically relevant toxicities (CRTs) compared with paclitaxel and trastuzumab (TH). In this end-of-study analysis, we report 5-year survival outcomes and correlative analyses from the trial. Methods: Patients with stage I centrally confirmed HER2+ breast cancer were randomly assigned 3:1 to adjuvant T-DM1 for one year or TH and received T-DM1 3.6 mg/kg IV every 3 weeks for 17 cycles or paclitaxel 80 mg/m2 IV with weekly trastuzumab IV followed by trastuzumab for 9 months. The co-primary objectives were to compare the incidence of CRTs between the 2 arms and to evaluate iDFS in patients receiving T-DM1. To investigate proteomic correlates of recurrence, spatial proteomic analyses were performed on samples from 13 patients experiencing iDFS events (cases) and 24 matched controls using the NanoString GeoMx Digital Spatial Profiler. The impact of HER2 heterogeneity on outcomes was investigated among 17 cases and 51 matched controls by fluorescence in-situ hybridization (FISH). HER2 genetic heterogeneity was assessed by scrutinizing the whole tumor area and defined as the occurrence of HER2 gene amplification in >5% but < 50% invasive tumor cells. The risk of recurrence was evaluated centrally with the HER2DX genomic assay from 225 primary tumor samples. Germline whole genome sequencing (WGS) was conducted among 55 patients experiencing T-DM1-induced thrombocytopenia and/or bleeding and 55 matched controls to identify genomic correlates for this side effect. Results: A total of 497 patients who initiated protocol therapy were included in this analysis (383 T-DM1 and 114 TH). After a median follow up 5.8 years, among patients receiving T-DM1 there were a total of 11 iDFS events, with 3 distant recurrences. The 5-year iDFS for T-DM1 was 97.0% (95% CI, 95.3-98.8%), the 5-year recurrence-free interval (RFI) was 98.6% (95% CI: 97.4-99.8%) and the 5-year overall survival (OS) for T-DM1 was 97.8 % (95% CI, 96.3-99.3%). Although the study was not powered to evaluate the efficacy of TH, among the 114 patients receiving TH, a total of 9 iDFS events were observed, including 2 distant events; the 5-year iDFS with TH was 91.3% (95% CI: 86.0-96.9%), 5-year RFI was 93.3% (95% CI: 88.6-98.2%) and 5-year OS was 97.9% (95% CI: 95.2-100%). A total of 56 samples were evaluable for heterogeneity analyses, among which 14% (n=8) harbored HER2 genetic heterogeneity. Spatial proteomic analyses found that NF1 (adjusted p=0.72 × 10-6) and CTLA-4 (adjusted p=0.15 × 10-3) were significantly upregulated in primary samples from cases, while cleaved caspase 9, CD25, GITR, ICOS, p53 and PD-L2 were significantly upregulated in controls (all with adjusted p< 0.05). Germline WGS found that the top gene associations with thrombocytopenia and thrombocytopenia or bleeding were ALMS1 (p=0,19 × 10-3) and APBA3 (p=0,23 × 10-3), respectively, although none reaching the threshold for genome wide significance. rs62143195 and rs114169776 were the top single nucleotide polymorphisms associated with thrombocytopenia and thrombocytopenia or bleeding, respectively. Data on the impact of HER2 heterogeneity and of HER2DX score on survival outcomes will be presented. Conclusion: With longer follow-up, adjuvant T-DM1 confirmed outstanding long-term outcomes among patients with stage I HER2+ breast cancer, demonstrating a 5-year RFI of 98.6%. Spatial proteomic analyses identified a potential association between NF1 and CTLA-4 expression with recurrence. Details on the impact of HER2 heterogeneity and HER2DX assay on prognosis will be presented. Citation Format: Paolo Tarantino, Nabihah Tayob, Chau T Dang, Denise Yardley, Steven J. Isakoff, Vicente Valero, Meredith Faggen, Therese Mulvey, Ron Bose, Douglas Weckstein, Antonio C. Wolff, Katherine Reeder-Hayes, Hope Rugo, Bhuvaneswari Ramaswamy, Dan Zuckerman, Lowell Hart, Vijayakrishna K. Gadi, Michael Constantine, Kit Cheng, Audrey Merrill Garrett, Paul K. Marcom, Kathy S. Albain, Patricia DeFusco, Nadine Tung, Blair Ardman, Rita Nanda, Rachel C. Jankowitz, Mothaffar Rimawi, Vandana Abramson, Paula R. Pohlmann, Catherine Van Poznak, Andres Forero-Torres, Minetta C. Liu, Kathryn Ruddy, Yue Zheng, Romualdo Barroso-Sousa, Adrienne Waks, Michelle K. DeMeo, Molly K. DiLullo, Giuseppe Curigliano, Harold Burstein, Ann Partridge, Eric Winer, Giuseppe Viale, Winnie Hui, Elizabeth A. Mittendorf, Bryan P. Schneider, Aleix Prat, Ian Krop, Sara Tolaney. Adjuvant Trastuzumab Emtansine Versus Paclitaxel plus Trastuzumab for Stage I HER2+ Breast Cancer: 5-year results and correlative analyses from ATEMPT (TBCRC033) [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD18-01.

Abstract Introduction Breast cancer is uncommon in men. Almost all male breast cancers are hormone receptor-positive, HER2-negative, although the pathogenesis is not always attributable to an endocrine condition. A few studies have compared biological characteristics or molecular signatures with breast cancers in women. We sought to evaluate whether hormone receptor-related gene expression is different in cancers from men compared to equivalent cancers from women. SET2,3 index measures non-proliferative hormone receptor-related transcriptional activity in the cancer (SET-ER/PR index) and adjusts this for a Baseline Prognosis Index (BPI) that combines the measurements of tumor and nodal stage with a 4-gene molecular subtype (ESR1, PGR, ERBB2, and AURKA). Methods We received aliquots of total RNA from male patients with breast cancer included in the retrospective cohort study of the EORTC 10085/BCG/TBCRC/BIG/NCTN International Male Breast Cancer Program (NCT01101425). SET2,3 assay was performed using the QuantiGene assay (Thermo Fisher) using bead-based hybridization and laser spectroscopy (Luminex). The statistical analyses were performed by the EORTC statistician. The primary objective of the study was the assessment of the prognostic value of the SET2,3 index score in patients with early-stage hormone receptor-positive, HER2-negative male breast cancer, treated with endocrine therapy. Clinical outcomes (recurrence-free survival – RFS; overall survival – OS) were estimated by Kaplan-Meier curves and secondarily compared using multivariable Cox models adjusted for continuous SET2,3 index, tumor size, nodal status, age, and chemotherapy and radiotherapy use. An exploratory analysis to compare the SET2,3 index scores distribution in female and male breast cancer patients was also performed using results from the same assay performed on cancers from women selected on the same inclusion criteria. Due to the low numbers of male patients treated with neoadjuvant treatment (N=6), this analysis was restricted to patients treated with adjuvant treatment (n=315 male and 660 female). Results Of the 321 male patients with breast cancer analyzed, treated between 1990 and 2010, 211 (65.7%) were categorized as high SET2,3 index score, reflecting a high endocrine activity in the cancer and low risk of recurrence, and 110 patients (34.3%) categorized as being low score, reflecting low endocrine activity and high risk of recurrence. At 5 years, the RFS was 75.0% (95% CI, 67.4-81.1) in the high SET2,3 group versus 60.7% (95% CI, 49.1-70.5) in the low SET2,3 group (HR univariate, 0.49; 95% CI, 0.34-0.70; P< 0.0001). The 5-year OS rate among patients with a high SET2,3 index was 84.3% (95% CI, 45.5-73.8), in contrast of 67.8% (95% CI, 56.6-76.7) in the low SET2,3 group (HR univariate, 0.44; 95% CI, 0.30-0.65; P< 0.0001). SET2,3 was independently prognostic for OS, but not RFS in multivariable Cox models. In patients classified as low SET2,3, the addition of neo/adjuvant chemotherapy to adjuvant endocrine therapy was associated with 5-year OS of 76.0% (95% CI, 59.5-86.4) and in patients who received endocrine therapy alone the 5-year OS was 61.3% (95% CI, 45.5-73.8), an absolute difference of 14.7 percentage points. Overall, we did not observe a difference in the distributions (median, interquartile range) of SET2,3 index between men (2.4, 1.9–2.6) and women (2.3, 2.0–2.7). Conclusion SET2,3 index measurements of endocrine-related transcriptional activity in male patients with breast cancer were not different from measurements in female patients with breast cancer. SET2,3 was prognostic in male breast cancer and our exploratory analysis suggests that chemotherapy might improve the poor prognosis for men with breast cancer that has low SET2,3 index. This study was funded by the Breast Cancer Research Foundation (BCRF). Citation Format: Danielle B. Zakon, Coralie Poncet, Fatima Cardoso, Neven Anouk, Vicente Valero, Stefan Aebi, Kim Benstead, Oliver Bogler, Lissandra Dal Lago, Judith Fraser, Carmela Caballero, Ingrid A. Hedenfalk, Larissa A. Korde, Barbro Linderholm, John WM Martens, Lavinia P. Middleton, Melissa Murray, Catherine M. Kelly, Cecilia Nilsson, Monika Nowaczyk, Stephanie Peeters, Melanie Beauvois, Peggy Porter, Carolien P. Schroder, Isabel T. Rubio, Kathryn Ruddy, Christi van Asperen, Danielle Van Den Weyngaert, Carolien HM van Deurzen, Elise van Leeuwen-Stok, Joanna M. Vermeij, John MS Bartlett, Antonio C. Wolff, Sharon H. Giordano, W. Fraser Symmans. PD6-11 Evaluation of the Sensitivity to Endocrine Therapy Index (SET2,3) in Early Male Breast Cancer: Results from an analysis in the EORTC 10085/TBCRC/BIG/NCTN International Male Breast Cancer Program [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD6-11.

Abstract Purpose: Cardiac toxicity is a serious potential complication of HER2-directed therapies and anthracyclines. HER2 codon 655 and SLC28A3 gene polymorphisms have been reported to be associated with cardiac toxicity from anti-HER2 and anthracycline therapy, respectively. Association of the polymorphism at HER2 codon 655 with prognosis has also been reported. Experimental Design: Whole blood samples from patients treated on a randomized adjuvant breast cancer trial (BCIRG-006) that compared chemotherapy with or without trastuzumab plus either anthracycline or nonanthracycline chemotherapy were tested for genetic polymorphisms in HER2 codon 655 and SLC28A3. Genotypes were correlated with cardiac function and disease-free survival (DFS) outcomes. Results: Of 3,222 patients enrolled in BCIRG-006, 662 patient samples were successfully genotyped for the rs1136201 allele in HER2 (codon 655): 424 (64%) were AA, 30 (4.5%) were GG, and 208 (31%) were AG genotype. In addition, 665 patient samples were successfully genotyped for the rs7853758 allele in the SLC28A3 gene: 19 (3%) were AA, 475 (71%) were GG, and 171 (26%) were AG genotype. Follow-up time was 10 years. No correlation between DFS, cardiac event rate, or mean left ventricular ejection fraction (LVEF) and rs1136201 genotype was seen in the trastuzumab-treated or non–trastuzumab-treated patients. Moreover, mean LVEF and cardiac event rates were similar in all rs7853758 genotype groups treated with anthracycline-based therapy. Conclusions: In the largest study to date to evaluate whether two polymorphisms are associated with DFS and/or cardiac toxicity in HER2-positive breast cancer treated with trastuzumab and/or anthracyclines, we observed no correlation.

Abstract BACKGROUND Brain mapping is the most reliable intraoperative tool for identifying surrounding functional cortical and subcortical brain parenchyma. Brain mapping procedures are nuanced and require a multidisciplinary team and a well-trained neurosurgeon. Current training methodology involves real-time observation and operation, without widely available surgical simulation. OBJECTIVE To develop a patient-specific, anatomically accurate, and electrically responsive biomimetic 3D-printed model for simulating brain mapping. METHODS Imaging data were converted into a 2-piece inverse 3D-rendered polyvinyl acetate shell forming an anatomically accurate brain mold. Functional and diffusion tensor imaging data were used to guide wire placement to approximate the projection fibers from the arm and leg areas in the motor homunculus. Electrical parameters were generated, and data were collected and processed to differentiate between the 2 tracts. For validation, the relationship between the electrical signal and the distance between the probe and the tract was quantified. Neurosurgeons and trainees were interviewed to assess the validity of the model. RESULTS Material testing of the brain component showed an elasticity modulus of 55 kPa (compared to 140 kPa of cadaveric brain), closely resembling the tactile feedback a live brain. The simulator's electrical properties approximated that of a live brain with a voltage-to-distance correlation coefficient of r 2 = 0.86. Following 32 neurosurgeon interviews, ∼96% considered the model to be useful for training. CONCLUSION The realistic neural properties of the simulator greatly improve representation of a live surgical environment. This proof-of-concept model can be further developed to contain more complicated tractography, blood and cerebrospinal fluid circulation, and more in-depth feedback mechanisms.

Abstract Neurosurgical training is being challenged by rigorous work-hour restrictions and the COVID-19 pandemic. 1 Now, more than ever, surgical simulation plays a pivotal role in resident education and psychomotor skill development. Three-dimensional (3D) printing technologies enable the construction of inexpensive, patient-specific, anatomically accurate physical models for a more convenient and realistic simulation of complex skull base approaches in a safe environment. 2 All stages of the surgical procedure can be simulated, from positioning and exposure to deep microdissection, which has an unparalleled educational value. The complex approach-specific anatomy, narrow working angles, and pathoanatomic relationships can be readily explored from the surgeon's perspective or point of view. 2,3 Furthermore, different thermoplastic polymers can be utilized to replicate the visual and tactile feedback of bone (cortical/cancellous), neurological, and vascular tissues. 4 Retrosigmoid craniectomies are widely used in neurosurgery with various applications, including microvascular decompressions in patients with trigeminal neuralgia. 5-7 Removal of the suprameatal tubercle (SMT) extends the retrosigmoid approach superiorly to the middle fossa and Meckel's cave, and anteriorly to the clivus. 8,9 This maneuver may be necessary in patients with prominent SMTs obstructing the view of the trigeminal nerve and in patients with a more anterosuperior neurovascular conflict. This video illustrates a microsurgical training tool for learning and honing the technique of retrosigmoid craniectomy and suprameatal drilling using an affordable (29.00 USD) biomimetic 3D-printed simulator that closely recapitulates not only the anatomy but also the tactile feedback of drilling and manipulating neurological tissues (see Table and Graph 1; minute 07:11) as it happens at the time of surgery.

PURPOSE The ATEMPT trial was designed to determine if treatment with trastuzumab emtansine (T-DM1) caused less toxicity than paclitaxel plus trastuzumab (TH) and yielded clinically acceptable invasive disease-free survival (iDFS) among patients with stage I human epidermal growth factor receptor 2–positive (HER2+) breast cancer (BC). METHODS Patients with stage I centrally confirmed HER2+ BC were randomly assigned 3:1 to T-DM1 or TH and received T-DM1 3.6 mg/kg IV every 3 weeks for 17 cycles or T 80 mg/m 2 IV with H once every week × 12 weeks (4 mg/kg load →2 mg/kg), followed by H × 39 weeks (6 mg/kg once every 3 weeks). The co-primary objectives were to compare the incidence of clinically relevant toxicities (CRTs) in patients treated with T-DM1 versus TH and to evaluate iDFS in patients receiving T-DM1. RESULTS The analysis population includes all 497 patients who initiated protocol therapy (383 T-DM1 and 114 TH). CRTs were experienced by 46% of patients on T-DM1 and 47% of patients on TH ( P = .83). The 3-year iDFS for T-DM1 was 97.8% (95% CI, 96.3 to 99.3), which rejected the null hypothesis ( P < .0001). Serially collected patient-reported outcomes indicated that patients treated with T-DM1 had less neuropathy and alopecia and better work productivity compared with patients on TH. CONCLUSION Among patients with stage I HER2+ BC, one year of adjuvant T-DM1 was associated with excellent 3-year iDFS, but was not associated with fewer CRT compared with TH.

PURPOSE Predictive biomarkers to identify patients with human epidermal growth factor receptor 2 (HER2)–positive breast cancer who may benefit from targeted therapy alone are required. We hypothesized that early measurements of tumor maximum standardized uptake value corrected for lean body mass (SULmax) on 18 F-labeled fluorodeoxyglucose positron emission tomography-computed tomography (PET-CT) would predict pathologic complete response (pCR) to pertuzumab and trastuzumab (PT). PATIENTS AND METHODS Patients with stage II or III, estrogen receptor–negative, HER2-positive breast cancer received four cycles of neoadjuvant PT. 18 F-labeled fluorodeoxyglucose positron emission tomography-computed tomography was performed at baseline and 15 days after PT initiation (C1D15). Eighty evaluable patients were required to test the null hypothesis that the area under the curve of percent change in SULmax by C1D15 predicting pCR is ≤ 0.65, with a one-sided type I error rate of 10%. RESULTS Eighty-eight women were enrolled (83 evaluable), and 85% (75 of 88) completed all four cycles of PT. pCR after PT alone was 22%. Receiver operator characteristic analysis of percent change in SULmax by C1D15 yielded an area under the curve of 0.72 (80% CI, 0.64 to 0.80; one-sided P = .12), which did not reject the null hypothesis. However, between patients who obtained pCR and who did not, a significant difference in median percent reduction in SULmax by C1D15 was observed (63.8% v 41.8%; P = .004) and SULmax reduction ≥ 40% was more prevalent (83% v 52%; P = .03; positive predictive value, 31%). Participants not obtaining a 40% reduction in SULmax by C1D15 were unlikely to obtain pCR (negative predictive value, 91%). CONCLUSION Although the primary objective was not met, early changes in SULmax predict response to PT in estrogen receptor–negative and HER2-positive breast cancer. Once optimized, this quantitative imaging strategy may facilitate tailoring of therapy in this setting.