Early-stage HER2-positive Breast Cancer Research Articles

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 .

Interim FDG-PET/CT for predicting response of HER2-positive breast cancer to neoadjuvant therapy: ECOG-ACRIN EA1211/DIRECT trial.

TPS614 Background: Strategies to optimize treatment decision-making in early stage HER2-positive breast cancer are a priority. Recent studies suggest that early metabolic changes on FDG-PET/CT predict response to HER2-directed therapy. The TBCRC026 trial showed that participants not obtaining a 40% reduction in SULmax by cycle 1 day 15 (C1D15) following neoadjuvant trastuzumab/pertuzumab (HP) were unlikely to obtain pCR [negative predictive value (NPV) 91%]. This trial aims to validate FDG-PET/CT as a neoadjuvant interim (niFDG-PET/CT) imaging integral biomarker in patients treated with standard HER2-directed regimens (NCT05710328). Methods: Trial design: EA1211/DIRECT is a multicenter, single-arm, primary imaging phase 2 study enrolling patients with stage II/III HER2-positive breast cancer. Patients undergo standard skull base-thigh FDG-PET/CT at baseline and C1D15 and receive standard of care pertuzumab-based neoadjuvant therapy followed by surgery. Eligibility: Age ≥18 years, ECOG performance status 0-2, stage IIa-IIIc, untreated HER2-positive breast cancer with known hormone receptor status, suitable to undergo FDG-PET/CT imaging and neoadjuvant therapy. Statistical methods: ΔSULmaxD15 will be computed as: (D15 SULmax – baseline SULmax)/baseline SULmax. The primary objective is to estimate the NPV of niFDG-PET/CT for pCR using ΔSULmaxD15 of the primary breast cancer at a threshold of 40%. NPV is defined as the probability that pCR will not be achieved by participants with ΔSULmaxD15 <40%. Secondary endpoints include evaluating sensitivity, specificity, and positive predictive value of ΔSULmaxD15 of the primary breast cancer at a threshold of 40% and ability of the niFDG-PET/CT biomarker to predict 3-year event free survival (EFS). Sample size: We expect that 50% of patients will not reach the ΔSULmax threshold of 40% and a pCR rate of 40-60%. The proposed sample size is 210 participants, adjusted to 235 to account for missing data in 10% of cases. Computation of exact, two-sided 95% confidence intervals (CI) for NPV determined the lower limit of the CI is at least 80% when the true NPV is at least 88%. The lower limit is 84% when the true NPV has the value of 91%, which was estimated in the TBCRC026 study. Current status: EA1211/DIRECT was activated in May 2023 across the NCI National Clinical Trials Network (NCTN) and is anticipated to complete in March 2025. Those interested in the clinical trial can email ea1211team@ecog-acrin.org. The EA1211/DIRECT trial is the first step in implementing a Response-Guided Treatment Strategy by validating the ΔSULmax threshold of 40% as the optimum cut point across standard of care HER2-directed neoadjuvant regimens. If EA1211/DIRECT meets its objectives, the results will be used to design clinical utility studies, thus hoping to change practice. Clinical trial information: NCT05710328 .

Neoadjuvant pegylated liposomal doxorubicin-containing chemotherapy in combination with trastuzumab and pertuzumab in patients with HER2-positive early breast cancer: A randomized phase II study (METIS).

596 Background: In the neoadjuvant phase, anti-HER2 therapy is usually delayed when combined with anthracycline-containing chemotherapy regimens, since conventional anthracycline and anti-HER2 agents cannot be given simultaneously. Pegylated liposomal doxorubicin (PLD) is a modified form of doxorubicin that can lower the risk of heart damage while preserving its anticancer activity. In this study, we aimed to explore whether PLD could replace conventional anthracycline and be used earlier with anti-HER2 agents to enhance neoadjuvant efficacy without increasing cardiotoxicity. Methods: The METIS study was an investigator-initiated, multicenter, open-label, randomized, phase II study conducted at 11 centers in China. Patients aged 18 to 70 years old with previously untreated stage II–III histologically documented HER2-positive breast cancer were randomly assigned (1:1) to receive PLD-containing or epirubicin-containing neoadjuvant chemotherapy. The PLD-containing regimen consisted of 4 cycles of PLD (35 mg/m2) and cyclophosphamide (600 mg/m2) every 3 weeks, followed by 4 cycles of a taxane of the investigator's choice (docetaxel, paclitaxel, or nab-paclitaxel). The epirubicin-containing regimen consisted of 4 cycles of epirubicin (90 mg/m2) and cyclophosphamide (600 mg/m2) every 3 weeks, followed by 4 cycles of a taxane of the investigator's choice. Both regimens included trastuzumab (8 mg/kg loading dose, then 6 mg/kg maintenance dose) and pertuzumab (840 mg loading dose, then 420 mg maintenance dose) every 3 weeks. Trastuzumab and pertuzumab were given with all chemotherapy cycles in the PLD-containing group, and with the taxane cycles only in the epirubicin-containing group. The primary end point was investigator-assessed total pathological complete response (tpCR) rate in the intention-to-treat population. Results: From August 2019 to March 2023, 156 were enrolled and randomly assigned to receive PLD-containing (n=80) or epirubicin-containing (n=76) treatment. At date of data analysis, the median follow-up duration was 16.3 months. The PLD-containing treatment group had a higher rate of pathological complete response (67.5%, 95% CI 56.1-77.6) than the epirubicin-containing group (48.7%, 95% CI 37.0-60.4), with a rate difference of 18.8% (p=0.033). Only one patient in the epirubicin-containing group experienced a grade 3 decrease in left ventricular ejection fraction, while none did in the PLD-containing group. Other adverse events were similar in both groups. Conclusions: A combination of PLD and cyclophosphamide with trastuzumab and pertuzumab, followed by a taxane, trastuzumab, and pertuzumab, significantly increased the rate of tpCR without more cardiotoxicity in neoadjuvant treatment for early-stage HER2-positive breast cancer patients. Clinical trial information: NCT04172259 .

Abstract PO3-09-02: Identifying risk factors for trastuzumab-induced cardiotoxicity among multi-ethnic women with HER2-positive early-stage breast cancer

Abstract Introduction: While trastuzumab, a HER2-targeted therapy for patients with HER2-positive breast cancer, has been shown to improve disease-free and overall survival rates, it also confers the risk of significant morbidity in the way of trastuzumab-induced cardiotoxicity (TIC). TIC may present as asymptomatic decline in left ventricular ejection fraction (LVEF) or as symptomatic heart failure. Given that racial/ethnic minorities are at higher risk for cardiovascular disease (CVD) compared to non-Hispanic Whites, our objective was to assess racial/ethnic differences in TIC and LVEF recovery among multi-ethnic patients with HER2-positive early-stage breast cancer. Methods: We conducted a retrospective cohort study including patients diagnosed with stage I-III HER2-positive breast cancer between 2007-2022 who had received adjuvant trastuzumab therapy at Columbia University Irving Medical Center (CUIMC) in New York, NY. TIC was defined as >10% decrease in LVEF to an overall LVEF< 50% and was confirmed by a minimum of two serial echocardiograms, whereas LVEF recovery was defined as a return to a LVEF >50%. Descriptive statistics, univariate and multivariate logistic regression analyses were conducted to estimate odds ratios (OR) and 95% confidence intervals (CI) for the associations between sociodemographic factors, tumor characteristics, treatment regimens, and CVD risk factors with the main outcome of TIC. Results: In the final cohort (N=500), median age was 53 years (IQR: 45.0-62.0) with 36.6% non-Hispanic White (NHW), 15.8% non-Hispanic Black (NHB), 27.8% Hispanic, and 19.8% Asian/Pacific Islander/Other. About 68.2% of patients received adjuvant radiation therapy, 30.2% were treated with anthracyclines, 37.8% with pertuzumab, 4.6% with T-DM1 and 69.0% with endocrine therapy. Fifty-three (10.6%) patients developed TIC, half of which experienced LVEF recovery. Compared to NHW, NHB patients had a higher rate of TIC (9.3% vs. 17.7%, respectively) and lower rate of LVEF recovery (70.6% vs. 21.4 % in those with TIC, respectively). On multivariable analysis, increasing age, lower LVEF at baseline, anthracycline exposure, and coronary artery disease (CAD) were associated with TIC (see Table). We found no association between TIC and use of pertuzumab or T-DM1. Discussion: In our racially/ethnically diverse study population, we found an incidence of TIC comparable to previous clinical studies. NHB patients had double the incidence of TIC and a lower incidence of LVEF recovery when compared to NHW patients. Given the observed racial disparities in TIC and LVEF recovery, NHB patients may require closer cardiac monitoring and restricted use of anthracyclines with adjuvant trastuzumab treatment. More research on cardiotoxicity associated with newer forms of HER2-targeted therapies is necessary. Table: Multivariable logistic regression model with outcome of TIC Citation Format: Leila Mishalani, Anna Vaynrub, Katherine Crew. Identifying risk factors for trastuzumab-induced cardiotoxicity among multi-ethnic women with HER2-positive early-stage breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-09-02.

Abstract PO4-01-03: Dual anti-HER2 Therapy with Pertuzumab and Trastuzumab versus Trastuzumab Alone in Addition to Anthracycline and Taxane-Based Neoadjuvant Therapy in Patients with HER2-Positive Early-Stage Breast Cancer; Real-World Data

Abstract Background: When use in the neoadjuvant setting, anti-HER2 targeted therapy had improved pathologic complete response rate (pCR) in patients with HER2-positive early-stage breast cancer (EBC). Here we present real-world data on the use trastuzumab with or without pertuzumab on the backbone of anthracycline and taxanes-based NSAPB-B27 chemotherapy regimen. Methods: We retrospectively reviewed records of patients with HER2-positive EBC who received neoadjuvant therapy using the National Surgical Adjuvant Breast and Bowel Project (NSABP)-B27 protocol (4 cycles of adriamycin and cyclophosphamide, followed by 4 more cycles of docetaxel; all given every 3 weeks) with anti-HER2 therapy from Jan 2014 to September 2021, treated at a tertiary care cancer center. The clinicopathological features, treatment received, and outcome were collected from patients’ electronic medical records. We estimated 3-year disease-free survival (DFS), a validated endpoint in HER2-positive EBC, using Kaplan-Meier with recurrence and/or death as events. Outcomes were reported in subgroups based on known prognostic factors. Results: The study comprised 528 patients with a median follow-up of 36 months. Median age was 48 (21-80) years. Hormone receptors (HR) were positive in 379 (71.8%), lymph node-involvement prior to neoadjuvant therapy was reported in 402 (76.1%) patients and 319 (60,4%) had grade-3 disease. Majority (n= 482, 91.3%) were labeled HER2-positive based on immunohistochemistry staining (IHC+3) and the rest were based on IHC+2 with positive FISH/ISH. Dual anti-HER2 therapy (trastuzumab and pertuzumab) was used in 316 (59.8%) patients, single agent trastuzumab in 173 (32.8 %) patients, while 39 (7.4%) others did not receive any anti-HER2 therapy. Except for 9 (1.7%) patients who progressed while on treatment, all patients underwent surgery. Among the whole group, 225 (43.4%) achieved pCR; significantly higher (n=80, 53.7%) in HR-negative compared to 38.3% among those with HR-positive disease, p=0.002. Additionally, pCR was higher in patients who received dual anti-HER2 (46.2%) compared to 39.3% for those treated with trastuzumab and 28.2% for those who did not receive anti-HER2 therapy. Following surgery, 463 (89.4%) of the patients received adjuvant trastuzumab, however, none of them received pertuzumab or TDM1 in adjuvant sitting. Estimated 3-year DFS was 86.1% with dual anti-HER2 and 83.0% with trastuzumab alone, p=0.19. However, DFS was better among those with node-negative disease; 96.5% compared to 80.9% in node-positive disease, p= < 0.001. Patients who achieved pCR had significantly better 3-year DFS; 89.3% compared to 80.2% in patients with residual disease, p= 0.006. Conclusions: Even with the wide use of pertuzumab in the neoadjuvant setting, the DFS was not improved compared to trastuzumab alone, and this highlights the importance of switching trastuzumab to TDM1, or to continue with pertuzumab in the adjuvant setting in patient with residual disease. Citation Format: Baha' Sharaf, Faris Tamimi, Osama Salama, Anas Zayed, Osama El Khatib, Suhaib Khater, Malek Horani, Suhaib Al-Sawajneh, Yosra AL-Masri, Hikmat Abdel-Razeq. Dual anti-HER2 Therapy with Pertuzumab and Trastuzumab versus Trastuzumab Alone in Addition to Anthracycline and Taxane-Based Neoadjuvant Therapy in Patients with HER2-Positive Early-Stage Breast Cancer; Real-World Data [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-01-03.

Abstract PO1-27-05: De-escalated neoadjuvant weekly nab-paclitaxel with trastuzumab and pertuzumab in HER2-positive early breast cancer (HELEN-006):a randomized,phase 3 trial

Abstract Background: Chemotherapy de-escalation is currently under investigation as a treatment approach for HER2-positive early-stage breast cancer(EBC). We conducted a phase 3 clinical trial to evaluate the effectiveness of a weekly regimen of nab-paclitaxel monotherapy in combination with dual HER2 blockade for HER2-positive EBC. Methods: We conducted a multicenter, randomized, open-label Phase 3 trial at six hospitals in China. Eligible participants were women aged 18-70 with locally confirmed, HER2-positive, stage II-III, invasive, operable breast cancer and an Eastern Cooperative Oncology Group performance status of 0 or 1. Participants were randomly assigned (1:1) using central block randomization, with block sizes of four, stratified by hormone receptor status, tumor stage, and node status. They were assigned to receive either intravenous nab-paclitaxel (125mg/m2 on days 1, 8, and 15) for six 3-week cycles (group A), or intravenous docetaxel (75mg/m² on day 1) and carboplatin (area under the concentration-time curve 6mg/mL per min on day 1) for six 3-week cycles (group B). Both groups received concurrent trastuzumab (8mg/m2 loading dose, 6mg/m2 maintenance dose on day 1) and pertuzumab (intravenous 840mg loading dose, 420mg maintenance dose on day 1). The primary endpoint was the proportion of patients achieving a pathological complete response(pCR) in the breast and axilla (ypT0/is ypN0) as determined by a local pathologist after surgery, assessed using a modified intention-to-treat analysis. To test for non-inferiority, we used a closed test procedure, considering the nab-paclitaxel group non-inferior to the docetaxel plus carboplatin group if the lower 95% confidence interval(CI) for the odds ratio (OR) was above 0.802, which accounted for a 5.5% non-inferiority margin (10% of the 55% pCR rate for docetaxel plus carboplatin and dual HER2 blockade regimen). We planned to test for superiority only if the non-inferiority test was positive, using an alpha value of 0.05. Safety was assessed in all patients who received the study drug. The trial is registered with ClinicalTrials.gov, with the registration number NCT04547907. Findings: Between September 10, 2020, and March 1, 2023, we randomly assigned 689 women, of whom 669 started treatment (332 with nab-paclitaxel and 337 with docetaxel plus carboplatin). The nab-paclitaxel group had a higher proportion of patients achieving a pCR (220 [66.3%, 95% CI 61.2-71.4]) compared to the docetaxel plus carboplatin group (194 [57.6%, 52.3-62.9]). The OR for pCR was 1.448 (95% CI 1.058-1.981), indicating a statistically significant difference (unadjusted p=0.021). Overall, 228 (34.1%) patients were noted to have at least one grade 3 or 4 event, 100(30.1%) in the nab-paclitaxel group and 128 (38.0%) in the docetaxel plus carboplatin group (P=0·032). The most common grade 3 or 4 events overall were nausea (98[14.6%] of 669 patients), diarrhea (80 [12.0%]), and neuropathy (51 [7.6%]).However, no treatment-associated deaths were identified. Conclusions: In neoadjuvant treatment of HER2-positive EBC, 18 weeks of nab-paclitaxel monotherapy combined with dual HER2 blockade has shown significantly higher pCR rates and improved tolerability compared to the standard docetaxel plus carboplatin and dual HER2 blockade regimen. These findings could potentially reshape preferences for neoadjuvant therapy in HER2-positive EBC. Patient Characteristics pCR by clinical-pathological variables Abbreviation:Nab-PHP,nanoparticle albumin-bound paclitaxel plus trastuzumab and pertuzumab; TCbHP,docetaxel plus carboplatin ,trastuzumab and pertuzumab; HR,hormone receptor; IHC,immunohistochemistry. *estrogen and/or progesterone receptor positive is classified as hormone receptor positive;estrogen and progesterone receptor negative is classified as hormone receptor negative Adverse events Abbreviation:Nab-PHP,nanoparticle albumin-bound paclitaxel plus trastuzumab and pertuzumab; TCbHP,docetaxel plus carboplatin ,trastuzumab and pertuzumab;ALT,alanine aminotransferase;AST,aspartate transaminase. Citation Format: Zhenzhen Liu, Xiuchun Chen, Jianghua Qiao, Jiao Dechuang, Chengzheng Wang, Xianfu Sun, Zhenduo Lu, Lianfang Li, Chongjian Zhang, Min Yan, Ya Wei, Chen Bo, Yueqing Feng, Miao Deng, Mingde Ma. De-escalated neoadjuvant weekly nab-paclitaxel with trastuzumab and pertuzumab in HER2-positive early breast cancer (HELEN-006):a randomized,phase 3 trial [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-27-05.

Abstract PO5-01-05: An Open-label, Single-center Study Assessing the Efficacy of PH-based Regimen as Neoadjuvant Therapy for HER2-positive Early-stage Breast Cancer: Integrating Genomic Features and Functional Imaging

Abstract Background: Pathological complete response (pCR) has been demonstrated as a surrogate endpoint for disease-free and overall survival in HER2-positive early-stage breast cancer (EBC). Trastuzumab (H) plus pertuzumab (P) improved pCR rates in patients with HER2-positive early-stage breast cancer. Nevertheless, biomarkers to assess the effectiveness of this treatment in the neoadjuvant setting are still unclear. This study aims to evaluate the effectiveness of fluorodeoxyglucose positron emission tomography (18F-FDG-PET) and 68 Ga-Affibody HER2 Imaging PET (HER2-PET) in HER2 EBC neoadjuvant therapy, and to identify novel biomarkers for this regimen. Methods: HER2-positive EBC patients were prospectively recruited at Fudan University Shanghai Cancer Center between April 2020 and March 2022. All patients received the 1 dose of HP, followed by 6 cycles of docetaxel (T), carboplatin (Cb), and HP. We use FoundationOne to evaluate the genomic alterations before treatment. In addition, 18F-FDG-PET and HER2 PET were performed at baseline, after 1 cycle of HP, and after 6 cycles of TCbHP, to assess the effectiveness of these examinations in the prediction of pCR and correlation to disease burden. All patients were received surgery and completed 1 year of HP-based regimen in the adjuvant setting. Results: A total of 61 patients with a median age of 49 years were included. Among them, 93.5% of patients are node positive. 75.8% of the patients reported adverse events (AEs), primarily grade 1 and 2. The incidence of serious AEs was 6.6%. Patients exhibiting a greater than 40% reduction in SUVmax of 18-FDG-PET or HER2-PET scans from baseline to the fifth day after the initial HP treatment were classified as the treatment-sensitive group. The pCR rate for the 18-FDG-PET-sensitive group was 79.3%, while for the insensitive group was 48.1%. For HER2-PET scans, the pCR rate was 70.0% in the sensitive group and 59.3% in the non-sensitive group. To evaluate the potential biomarkers, 25 patients (13 pCR and 12 non-pCR) were evaluated with FoundationOne, with the identification of 1,321 somatic alterations. The most frequently altered genes were ERBB2 (100%), TP53 (96%), CDK12 (76%), MYC (56%), CCND1 (44%), PIK3CA (40%), and SRSF2 (36%). In the pCR group, we found PPM1D (38.5%) and RAD21 (38.5%) were altered more frequently than the non-pCR group. PIK3CA alterations were significantly reduced in pCR group, only 23% of cases are affected compared to 58.3% in non-pCR group. Patients were non-pCR had more MDM4 (41.7%) and ZNF217 (41.7%) alterations than pCR patients. Conclusion: The SUVmax value of 18-FDG-PET and HER2-PET scans are correlated well with the tumor burden and the residual disease in the HER2 EBCs. The reduction of SUVmax could predict pCR but need further exploration. Patients with alterations in PPM1D and RAD21 have a favorable response to the TCbHP regimen. Conversely, alterations in PIK3CA, MDM4, and ZNF217 are associated with treatment resistance. These results indicate the significance of 18-FDG-PET and HER2-PET in monitoring treatment effectiveness. The biomarker analysis in this study will help us understand the mechanism of HER2 positive breast cancer treatment resistance and assisting in tailoring personalized therapy. Clinical trial information: NCT04281641. Citation Format: Ming Chen, Benlong Yang, Sun Yuyun, Linxiaoxi Ma, Song Shaoli, Min He, Zhi-Ming Shao, Bingqiu Xiu, Jiong Wu. An Open-label, Single-center Study Assessing the Efficacy of PH-based Regimen as Neoadjuvant Therapy for HER2-positive Early-stage Breast Cancer: Integrating Genomic Features and Functional Imaging [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-01-05.

Abstract PO1-01-06: Patterns in use and tolerance of adjuvant neratinib in patients with hormone receptor (HR)-positive, HER2-positive early-stage breast cancer

Abstract Background: In the ExteNET study, 1 year of neratinib therapy was shown to derive a significant invasive disease-free survival (iDFS) benefit in HR+, HER2+, node-positive disease after trastuzumab-based adjuvant therapy. Currently, the NCCN guidelines recommend extended adjuvant neratinib following trastuzumab-based therapy for patients (pts) with high-risk HR+ HER2+ disease. Limitations to use of neratinib include significant gastrointestinal side effects which often result in pts discontinuing treatment. In this study, we aimed to identify high-risk clinical features and characteristics of pts who were offered adjuvant neratinib therapy and factors that impacted treatment completion versus discontinuation. Methods: We performed a retrospective review of all pts with early-stage HR+ HER2+ breast cancer who were prescribed neratinib from 2017-2023 at our institution. We used the electronic medical record to extract information on patient characteristics, clinical and high-risk features. High-risk was defined as any of the following: at least 4 lymph nodes positive for disease, 1-3 lymph nodes positive for disease and a grade 3 (poorly differentiated) tumor, tumor > 5 cm, or Ki67 > 20%. Length of time on treatment, treatment holds, dose reductions and up-titrations were documented. Statistical analysis was performed using two-sided T-tests and chi-square tests. Results: We identified 62 eligible pts of whom 34 (55%) completed 1 year of neratinib and 28 (45%) did not. Median age at diagnosis was 51.5 years. 49% of pts were pre-menopausal at diagnosis, 43% were post-menopausal, 5% were peri-menopausal and 3% had undocumented menopausal status at diagnosis. Clinical features of the pts are documented in Table 1. Sixty percent of patients offered neratinib were considered high-risk at diagnosis, based on definitions described above. 73% of pts received neoadjuvant treatment with pertuzumab in addition to trastuzumab. 24 pts (39%) had residual disease and 22 pts (35%) received adjuvant T-DM1. The most common reason for neratinib discontinuation was inability to tolerate side effects (54%) followed by pill burden (18%). The most common side effect experienced by pts was diarrhea despite anti-diarrheal prophylaxis (56%), followed by rash (8%). Pts who received an up-titration of neratinib were more likely to complete the full course of neratinib when compared to those who did not (76% vs. 40.5% p = 0.013). The median starting dose of those who completed neratinib treatment was 140 mg vs. 240 mg in those who did not (p = 0.016). The median length of time on neratinib for those that did not complete the 1-year treatment course was 30 days. Neither group experienced a statistically significant greater likelihood of treatment holds or dose reductions. In terms of outcomes, 10 pts had progression of disease of whom 7 did not complete neratinib treatment (p = 0.169). Interestingly, those 7 pts developed metastatic disease and 57% had central nervous system metastases. Conclusions: Pts are more likely to complete 1 year of adjuvant neratinib with dose up-titration. Dose reductions and interruptions did not affect neratinib adherence in our patient population. Seven pts in our study developed metastatic disease, all of whom did not complete adjuvant neratinib treatment. Future prospective studies are needed to further determine the impact of adjuvant neratinib treatment on iDFS in pts who have received pertuzumab and/or T-DM1. Table 1: Clinical Features of Patients Prescribed Neratinib Citation Format: Julia Blanter, Elena Baldwin, Rima Patel, Tianxiang Sheng, Amy Tiersten. Patterns in use and tolerance of adjuvant neratinib in patients with hormone receptor (HR)-positive, HER2-positive early-stage breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-01-06.

Abstract PO1-27-01: Comparing the Efficacy and Safety of TQB2440 versus the Reference Pertuzumab for the Treatment of HER2-Positive Early or Locally Advanced Breast Cancer: A Multicenter, Randomized, Double-Blind, Parallel-Controlled Phase 3 Trial

Abstract Background: Pertuzumab is a recombinant humanized monoclonal antibody targeting the extracellular dimerization domain II of HER2. On September 30, 2013, the FDA have granted accelerated approval of a pertuzumab regimen for neoadjuvant treatment of patients (pts) with high-risk, HER2-positive early stage breast cancer. TQB2440 is a pertuzumab (Perjeta®, Roche) biosimilar. This study aimed to compare the efficacy and safety of TQB2440 and the reference pertuzumab combined with trastuzumab and docetaxel in pts with HER2-positive early or locally advanced breast cancer. Methods: In this multicenter, randomized, double-blind phase 3 study, eligible pts were aged 18-75 with operable HER2-positive (IHC 3+ or ISH+) clinical stage II-IIIC breast cancer negative for ER/PR and had an ECOG PS of 0-1. The pts were randomly assigned to receive either TQB2440 or the reference pertuzumab (Perjeta®) (840 mg on day 1, cycle 1, followed by 420 mg on cycle 2-4, q3w) added to trastuzumab (8 mg/kg on day 1, cycle 1, followed by 6 mg/kg for cycles 2-4, q3w) + docetaxel (75 mg/m2, cycle 1-4, q3w). The pts then underwent surgery followed by adjuvant treatment with FEC regimens (fluorouracil 600 mg/m², epirubicin 90 mg/m², cyclophosphamide 600 mg/m², cycle 5-7, q3w), then TQB2440 (840 mg on day 1, cycle 8, followed by 420 mg on cycle 9-20, q3w) + trastuzumab (8 mg/kg on day 1, cycle 8, followed by 6 mg/kg for cycles 9-20, q3w) or until disease progression or intolerable toxicity. The primary endpoint was total pathologic complete response (tpCR) by independent review committee (IRC). Equivalence was established if the 90% confdence intervals (CIs) of the relative ratio [RR] within the interval of 0.76 to 1.32. Secondary endpoints included breast pathologic complete response (bpCR) by IRC, tpCR & bpCR by investigator, breast conserving surgery (BCS) rates, objective response rate (ORR), event-free survival (EFS), disease-free survival (DFS), OS and safety. Results: Between October 21, 2020, and November 21, 2022, 412 pts were enrolled (TQB2440 group, n=207; the reference pertuzumab group, n=205). Data cutoff was November 30, 2022. In the intention-to-treat (ITT) population, the tpCR by IRC of the TQB2440 group and the reference drug group were 58.94% and 58.05%, respectively. The RR was 1.02 (90% CI, 0.89, 1.16), which was within the predefined equivalence interval of 0.76 to 1.32. There was no statistically significant difference in the bpCR by IRC between the TQB2440 group and the reference pertuzumab group (67.63% [95% CI, 60.80%, 73.95%] vs. 63.90% [95% CI, 56.92%, 70.48%], P=0.4249). The BCS rate also comparable between the two groups with 13.04% (95% CI, 8.77%, 18.41%) vs. 13.17% (95% CI, 8.86%, 18.58%) (P=0.9695). Additionally, the results of the PP (per-protocol) population were similar to those of the ITT population. The incidence of treatment-related adverse events (TRAEs) and grade ≥3 TRAEs were similar between the TQB2440 group and the reference pertuzumab group with 79.71% vs. 75.98% and 49.28% vs. 41.67%, respectively. Conclusion: In patients with HER2-positive early or locally advanced breast cancer, TQB2440 demonstrated equivalent efficacy and similar safety to the reference pertuzumab. Clinical trial information: NCT05985187. Research Sponsor: Chia Tai Tianqing Pharmaceutical Group Co., Ltd Citation Format: Qingyuan Zhang, Shusen Wang, Nanlin Li, Qiao Cheng, Yu ren, Xuchen Cao, Jianjun Huang, Caigang Liu, Hongwei Yang, Limin Wei, Zhangjun Song, Huadong Zhao, Fangling Ning, Xiaojia Wang, Dehong Zou, Xiaohua Zeng, Jie Hao, Yunjiang Liu, Huijuan Wang, Nie Jianyun, Liang Li, Lina Liu, Tao Sun, Xiaobo Hu, Zhenhua Zhai, Huihua Xiong, Yuanqi Zhang, Enxiang Zhou, Jing Sun, Zhenhai Cai, Antai Zhang, Shui Wang, Junyang Mo, Qun Su, Xiuheng Qi, Guoren Zhou, Shuqun Zhang, Guozhong Cui, Wei Wang, Mingjiang Fan, Xinyu Qian, Xinhong Wu, Zhihong Wang, Jiuda Zhao, Yonghui Luo, Yanming Zhang, Fuguo Tian, Jiye Zhang, Dongning Chai, Qingshan Li. Comparing the Efficacy and Safety of TQB2440 versus the Reference Pertuzumab for the Treatment of HER2-Positive Early or Locally Advanced Breast Cancer: A Multicenter, Randomized, Double-Blind, Parallel-Controlled Phase 3 Trial [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-27-01.

Abstract PO1-01-01: ECOG-ACRIN EA1211: Interim FDG-PET/CT for predicting response of HER2-positive breast cancer to neoadjuvant therapy (DIRECT Trial)

Abstract Background: Strategies to optimize treatment decision-making in early stage HER2-positive breast cancer are a current priority for the oncology and patient advocacy community. Recent studies suggest that early metabolic changes on FDG-PET/CT (imaging biomarker) predict response to HER2-directed therapy. The TBCRC026 trial showed that participants not obtaining a 40% reduction in SULmax by cycle 1 day 15 (C1D15) following neoadjuvant trastuzumab/pertuzumab (HP) were unlikely to obtain pCR [negative predictive value (NPV) 91%]. The ECOG-ACRIN EA1211/DIRECT trial aims to validate FDG-PET/CT as a neoadjuvant interim (niFDG-PET/CT) imaging integral biomarker in patients treated with standard HER2-directed regimens (NCT05710328). Design: EA1211/DIRECT is a multicenter, single-arm, primary imaging phase 2 study enrolling patients with stage II/III HER2-positive breast cancer. Patients undergo standard skull base-thigh FDG-PET/CT at baseline and C1D15 and receive standard of care pertuzumab-based neoadjuvant therapy followed by surgery. Eligibility: Age ≥18 years, ECOG performance status 0-2, stage IIa-IIIc, untreated HER2-positive breast cancer with known hormone receptor status, suitable to undergo FDG-PET/CT imaging and neoadjuvant therapy. Methods: ΔSULmaxD15 will be computed as: (D15 SULmax – baseline SULmax)/baseline SULmax. The primary objective is to estimate the NPV of niFDG-PET/CT for pCR using ΔSULmaxD15 of the primary breast cancer at a threshold of 40%, in patients treated with neoadjuvant HER2-directed therapy. NPV is defined as the probability that pCR will not be achieved by participants with ΔSULmaxD15 < 40%. Secondary endpoints include evaluating the sensitivity, specificity, and positive predictive value of ΔSULmaxD15 of the primary breast cancer at a threshold of 40% and the ability of the niFDG-PET/CT biomarker to predict 3-year event free survival (EFS). Sample Size: We expect that 50% of patients will not reach the ΔSULmax threshold of 40% and a pCR rate of 40-60%. The proposed sample size is 210 participants, adjusted to 235 to account for missing data in 10% of cases. Computation of exact, two-sided 95% confidence intervals (CI) for NPV determined the lower limit of the CI is at least 80% when the true NPV is at least 88%. The lower limit is 84% when the true NPV has the value of 91%, which was estimated in the TBCRC026 study. Current Status: EA1211/DIRECT was activated in May 2023 across the NCI National Clinical Trials Network (NCTN), and accrual is anticipated to complete in March 2025. Those interested in the clinical trial can email ea1211team@ecog-acrin.org. Conclusion: The EA1211/DIRECT trial is the first step in implementing a Response-Guided Treatment Strategy by validating the ΔSULmax threshold of 40% as the optimum cut point across standard of care HER2-directed neoadjuvant regimens. If EA1211/DIRECT meets its objectives, the results will be used to design clinical utility studies, and thus hoping to change practice. Citation Format: Heather Jacene, Constantine Gatsonis, Roisin Connolly, Brian Burnette, Erica Stringer-Reasor, Maeve Hennessy, Justin Romanoff, Alexander Taurone, Ciara O'Sullivan, H. T. Carisa Le-Petross, Courtney Lawhn Heath, Vered Stearns, Amy Fowler, Shou-Ching Tang, Karla A Sepulveda, Angela DeMichele, David Mankoff, Antonio Wolff. ECOG-ACRIN EA1211: Interim FDG-PET/CT for predicting response of HER2-positive breast cancer to neoadjuvant therapy (DIRECT Trial) [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-01-01.

Abstract PO4-25-04: MHC Class I and II Expression, Functional Tertiary Lymphoid Structure (TLS), and Outcomes in Early-Stage HER2-Positive (HER2+) Breast Cancer in NCCTG N9831 (Alliance)

Abstract Background: Tertiary lymphoid structure (TLS) is an organized form of ectopic lymphoid aggregates (LA) with secondary lymphoid organ structure. Several studies showed that the presence of TLS associates with improved outcomes in multiple cancers when treated with immune checkpoint inhibitors. However, data is currently limited regarding TLS and outcomes in HER2+ breast cancer patients (pts) treated with adjuvant trastuzumab. Furthermore, distinguishing TLS and simple LA is challenging in standard hematoxylin and eosin (H&E) staining, particularly when the germinal center is absent. Emerging studies also showed the prognostic value of MHC expression in breast cancer but mainly in triple-negative breast cancer. In this study, we evaluated integrated pathological quantification and genomic data to assess functional TLS in association with MHC expression and outcomes in the N9831 trial. Methods: Pathological evaluation of LA in H&E slides from pts treated in Arm A (chemotherapy alone) and Arm C (chemotherapy with concurrent trastuzumab) in N9831 was performed. NanoString was used to quantify mRNA of MHC class I and II expression as well as TLS-related immune genes, including IFNG, ICOSLG, CXCL13, CXCR3, BCL6, IL21R, ICOS, PDCD1, CXCR5, CXCL9, TBX21, CD38, CXCL10, CLXCL11, IL21, CD200, CD19, MS4S1. Wilcoxon rank sum test, Chi-squared test, Kaplan-Meier method, and Cox regression model were used to evaluate the association between LA and baseline characteristics, MHC expression, and outcomes. Results: LA was evaluated in 526 pts in Arm A and 485 in Arm C. Greater number of LA was significantly associated with stromal tumor-infiltrating lymphocytes (sTILs), hormone receptor negative, and higher tumor grade, but not stage and age. Using multivariable Cox regression analysis, increasing numbers of LA were associated with improved recurrence-free survival in both arms combined (RFS, p 0.028). However, when evaluating each arm separately, LA was associated with improved RFS only in Arm A (HR 0.6, 95%CI 0.43-0.84, p 0.003) but not in Arm C (HR 0.72, 95%CI 0.47-1.1, p 0.134). We further evaluated TLS-related immune genes in 252 pts in Arm C with LA ≥ 1. As a continuous variable, higher expression of BCL6 (HR 0.61, 95%CI 0.41-0.92, p 0.019) and IL21R (HR 0.78, 95%CI 0.62-0.98, p 0.03) were associated with improved RFS in Arm C pts with LA ≥ 1. However, these genes were not significantly associated with outcomes in Arm C pts without LA with BCL6 (HR1.07, 95%CI 0.67-1.71, p 0.776) and IL21R (HR 0.96, 95%CI 0.71-1.29, p 0.775). Moreover, we evaluated differential gene expression between tumors with LA ≥ 1 with high BCL6 vs. LA 0. All MHC class I and II (HLA A, B, C, E, DQ, DM, DO, DP, and DQ) were significantly higher in tumors with LA ≥ 1 with high BCL6 (p < 0.001). Conclusion: A greater number of LA was associated with improved outcomes in pts with early-stage HER2+ breast cancer, particularly when treated with chemotherapy alone. Using histologic and genomic integration with the combination of pathological LA and TLS-related immune genes, we identified that pts with functional TLS with LA ≥ 1 and higher expression of BCL6 or IL21R had significantly improved outcomes when treated with trastuzumab. High MHC class I and II expressions are associated with the presence of functional TLS, underscoring the crucial role of antigen presentation in the generation of an effective adaptive immune response. Support: U10 CA180821, U10 CA180882, U24 CA196171, https://acknowledgments.alliancefound.org; Genentech; Clinicaltrials.gov Id: NCT00005970 Citation Format: Saranya Chumsri, Tracy Shachner, Zhuo Li, Nadine Norton, Alvaro Moreno-Aspitia, Gerardo Colon-Otero, Edith Perez, Aziza Nassar, E. Thompson, Keith Knutson. MHC Class I and II Expression, Functional Tertiary Lymphoid Structure (TLS), and Outcomes in Early-Stage HER2-Positive (HER2+) Breast Cancer in NCCTG N9831 (Alliance) [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-25-04.

Abstract PO3-17-05: Clinical Characteristics and Outcomes of Patients Receiving Adjuvant Paclitaxel and Trastuzumab (APT regimen) for HER2-Positive Early-Stage Breast Cancer in Brazil: A Real-World Evidence

Abstract Introduction: The APT trial established adjuvant paclitaxel and trastuzumab (TH) as the standard of care for HER2-positive early-stage breast cancer with tumor size ≤ 3 cm and no more than one lymph-node micrometastasis. This single-arm phase II trial demonstrated favorable long-term outcomes, with a 3-year invasive disease-free survival (IDFS) rate of 98.7% (95% CI 97.6 – 99.8%). In an updated follow-up analysis, the 10-year IDFS and overall survival (OS) rates were 91.3% (95% CI 88.3 – 94.4%) and 94.3% (95% CI 91.8 – 98.3%), respectively. Nevertheless, outcomes observed in real-world scenarios have frequently been less favorable than those observed in clinical trials. We aimed to characterize the population receiving the APT regimen in clinical practice and evaluate if real-world outcomes align with those observed in the pivotal clinical trial. Methods: This retrospective cohort study included patients with HER2-positive early-stage breast cancer treated between 2015 and 2023 at four Brazilian cancer institutions, including public and private hospitals. Clinical and demographic data, treatment details, and outcomes were collected from electronic records. The primary endpoints were the 3-year and 7-year invasive disease-free survival (IDFS) rates. Secondary endpoints included overall survival (OS) and factors associated with IDFS. Survival analysis employed the Kaplan-Meier method, and Cox regression assessed prognostic factors. Results: A total of 133 patients treated with the APT regimen were evaluated, with a median age of 56 years (range 20–83). The majority had no special type breast carcinoma (92.4%), grade 2 (63.4%) or grade 3 (34.3%) tumors, no angiolymphatic invasion (76.3%), positive estrogen receptor (69.9%), positive progesterone receptor (55.6%), and node-negative disease (94.7%). Tumor staging distribution was as follows: T1a (12%), T1b (23.3%), T1c (49.6%), and T2 (13.5%). Most patients (95.4%) received the APT regimen as per guideline recommendations, while 3.8% received it due to contraindication to other therapies. With a median follow-up of 45.8 months, 8 patients (5.8%) experienced an invasive disease event or death from any cause: 5 (3.8%) had distant recurrence, 1 (0.8%) had local recurrence, and 2 (1.5%) died without recurrence. Notably, these events occurred in patients receiving the APT regimen according to standard indications, except for one patient with N+ disease and a contraindication to another regimen. The recurrence rate according to the T stage is presented in the Table. The 3-year IDFS rate was 100% (95% CI not applicable). All events occurred after the 3-year time point, resulting in a 7-year DFS rate of 80.8% (95% CI 62.7–90.7%). No prognostic factors related to IDFS were identified. Four patients died during the study period, yielding a 7-year OS rate of 88.0% (95% CI 61.6–96.6%). Conclusion: While the baseline characteristics of this cohort resembled those of the APT trial, the long-term outcomes observed in the real-world setting were less favorable. Further investigation is required to determine the reasons for this discrepancy, underscoring the necessity for larger real-world data studies to validate these findings. Recurrence rate according to T stage XX XX Citation Format: Giselle Carvalho, Renata Colombo Bonadio, Pedro Bergmann, Marina Nishimuni, André Rossi, Cristiano Souza, Gabriel Guimarães, Laura Testa, José Bines. Clinical Characteristics and Outcomes of Patients Receiving Adjuvant Paclitaxel and Trastuzumab (APT regimen) for HER2-Positive Early-Stage Breast Cancer in Brazil: A Real-World Evidence [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-17-05.

Abstract PO3-01-02: Real world outcomes of neoadjuvant therapy with Trastuzumab and Pertuzumab associated with carboplatin and docetaxel (TCHP) in HER2+ early breast cancer patients unfit for anthracyclines: a retrospective cohort comparative study

Abstract Backgound Neoadjuvant chemotherapy (CT) with anti-HER2 blockade using trastuzumab (H) and pertuzumab (P) is a standard of care for patients (pts) with HER2-positive early-stage Breast Cancer (eBC). Historically, taxanes (T) and anthracyclines (A) have been the mainstays of (neo)adjuvant CT in this setting, but the added benefit of A in the era of anti-HER2 therapy has been questioned. This study aimed to assess the effectiveness, cardiac safety, and cost-effectiveness of an anthracycline-free regimen (TCHP) in a real-world population of pts deemed unfit for A, compared to pts treated with the standard regimen of doxorubicin and cyclophosphamide plus dual-blockade associated with docetaxel (AC-DHP) at a single Portuguese Comprehensive Cancer Center. Methods This retrospective cohort study included a consecutive series of female eBC HER2+ pts who initiated primary treatment with TCHP between July 2018 and August 2022. The primary endpoint was pathological complete response (pCR), and secondary endpoints were cardiac safety and disease-free survival (DFS). The outcomes were compared with a historical database of eBC HER2+ pts who started primary treatment with AC-DHP between August 2015 and May 2021. Clinical data was collected from medical and administrative records. Descriptive statistics were used to describe categorical and continuous variables, and the Kaplan-Meier method was used for DFS analysis. Costs analysis employed the micro-costing technique, considering individual medical direct costs from diagnosis until surgery. Multivariate logistic regression models were used for effectiveness analysis and the gamma general model for costs analysis. The incremental cost-effectiveness ratio (ICER) was calculated using the pCR rate as a measure of effectiveness. Results A total of 233 and 23 pts were included in the TCHP and AC-DHP groups respectively. Reasons for choosing the anthracycline-free regimen in the TCHP group were primarily age-related frailty (52%), medical comorbidities (26%), and previous exposure to anthracyclines (22%). The TCHP pts were older (median age 71 years, range [45-77] vs. 47 years [24-70]) and had lower baseline Left Ventricular Ejection Fractions (LVEF) (median 65% [51-80] vs. 60% [56-73]), with a higher proportion of hormone receptor (HR) negative pts (78.3% vs. 33.0%). Clinical stages were balanced between groups, but the TCHP group had a higher nodal involvement (N+) (73.9% vs. 61.8%). The pCR rates were higher in the TCHP group (65.2% vs. 46.1%, HR 0.98 [95% CI 0.36 - 2.70]). Subgroup analysis by HR status showed comparable pCR rates: 77.1% vs. 74.1% in HR- pts and 40% vs. 39.7% in HR+ pts. Cardiac safety analysis indicated a median decrease in LVEF of 9% in both the TCHP and AC-DHP groups, with 43.5% of TCHP pts experiencing a decline of 10% or more, and 13.0% dropping below 50%. In comparison, these figures were 44.2% and 3.9%, respectively, in the AC-DHP group. At the end of the follow-up, only one patient in the TCHP group with a LVEF < 50% persisted with mild symptoms of chronic heart failure. The median follow-up time for DFS events, starting from surgery, was 31.1 months in the TCHP group and 45.7 months in the AC-DHP group, with 1-year DFS rates of 91.3% and 100%, respectively. The ICER analysis indicated that TCHP was cost-effective, as the incremental cost for achieving an additional pCR in similar subgroups can be outweighed by later cost savings, mainly due to further adjuvant treatment with trastuzumab instead of TDM-1. Conclusions In a real-world population of HER2+ eBC patients unfit for anthracyclines, the TCHP regimen demonstrated a higher overall pCR rate compared to a historical control treated with the AC-DHP regimen, along with an acceptable cardiac safety profile. These results support the broader use of the TCHP regimen in HER2+ eBC pts, as recommended by current NCCN guidelines. However, larger studies involving similar populations are needed to provide higher levels of evidence. Citation Format: Ricardo Pinto, Rita Calisto, Patrícia Redondo, Ana Silva, Pedro Castro, Rute Fernandes, Raquel Teixeira, Diana Mata, Ana Ferreira, Maria Bento, Cláudia Vieira. Real world outcomes of neoadjuvant therapy with Trastuzumab and Pertuzumab associated with carboplatin and docetaxel (TCHP) in HER2+ early breast cancer patients unfit for anthracyclines: a retrospective cohort comparative study [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-01-02.

Abstract ED05-03: Surgical management of Stage I TN and HER2+ breast cancer

Abstract The management of early-stage triple-negative (TN) and HER2-positive (HER2+) breast cancer has evolved significantly with continually improving systemic therapies. The use of neoadjuvant chemotherapy (NAC) has become standard for stage II disease, for both surgical downstaging and assessment of response to treatment, allowing for tailoring of systemic therapy in the adjuvant setting. However, the optimal treatment approach for stage I TN and HER2+ disease remains controversial, given the limited burden of disease at presentation with most patients considered candidates for limited surgery, and the excellent overall outcomes with de-escalated systemic therapy regimens in the adjuvant setting. This presentation will discuss the evolving landscape and current standards for stage I TN and HER2+ disease. Citation Format: A. Mamtani. Surgical management of Stage I TN and HER2+ breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr ED05-03.

Abstract PO4-18-04: An exploratory study of Trastuzumab Deruxtecan neoadjuvant therapy in HER2-positive or HER2-low early or locally advanced breast cancer after a poor response to neoadjuvant chemotherapy

Abstract Background The current standard of care for neoadjuvant treatment of HER2-positive early-stage breast cancer consists of dual HER2-blockade with trastuzumab (H) plus pertuzumab (P) and polychemotherapy with a pathological complete response (pCR) rate of 31%~50%. Trastuzumab deruxtecan (T-DXd) is an antibody-drug conjugate composed of an anti-HER2 antibody, a cleavable tetrapeptide-based linker, and a cytotoxic topoisomerase I inhibitor. T-DXd significantly prolonged progression-free and overall survival vs trastuzumab emtansine in HER2-positive unresectable and/or metastatic breast cancer (mBC) previously treated with H and taxane in DESTINY-Breast03 study. HER2-low breast cancer is currently treated as HER2-negative (HER2-low and HER2-zero) breast cancer, with patients stratified according to hormone-receptor (HR) status. In DESTINY-Breast04 study, T-DXd resulted in significantly longer progression-free and overall survival than the physician’s choice of chemotherapy in HER2-low mBC. Given the efficacy of T-DXd monotherapy in HER2-positive or HER2-low mBC, we conduct an exploratory study to evaluate the efficacy and safety of T-DXd in HER2-positive or HER2-low early or locally advanced breast cancer after a poor response to neoadjuvant chemotherapy, and to identify sensitive biomarkers for T-DXd neoadjuvant therapy. Methods Eligible patients were women aged 18 years to 75 years with clinical stage cT2–cT4/cN0–cN3/cM0 (stage II–III) invasive breast cancer (>2 cm in size) confirmed as HER2-positive (immunohistochemistry [IHC] 3+) or HER2-low (IHC2+ or IHC1+/situ hybridization-negative). Patients are required to have an Eastern Cooperative Oncology Group performance status of 0 or 1, and baseline left ventricular ejection fraction of at least 55% (as measured by echocardiogram). Patients are also required to have adequate organ function and bone marrow function. Patients with HER2-positive breast cancer should receive taxane (paclitaxel or nab-paclitaxel) or docetaxel, carboplatin, and H plus P for 2 cycles. Patients with HER2-low and HR-positive breast cancer should receive taxane (paclitaxel or nab-paclitaxel) or docetaxel, and cisplatin or carboplatin for 2 cycles. Patients with HER2-low and HR-negative breast cancer should receive taxane (paclitaxel or nab-paclitaxel) or docetaxel, and anthracycline (epirubicin, pirarubicin or liposomal doxorubicin) for 2 cycles. For patients who have responses of stable disease assessed by magnetic resonance imaging will receive T-DXd neoadjuvant therapy. T-DXd will be administered intravenously every 3 weeks at a dose of 5.4 mg per kilogram of body weight for 4 cycles. Peripheral blood and biopsy tissue will be collected before neoadjuvant chemotherapy and T-DXd neoadjuvant therapy, and peripheral blood and surgical tissue will be collected after the surgery. Lipid metabolites in peripheral blood and mass spectrometry-based protein quantification in tissue will be detected to find sensitive biomarkers for T-DXd neoadjuvant therapy. The primary endpoint is pCR rate (ypT0/Tis ypN0) and identify sensitive biomarkers for T-DXd neoadjuvant therapy. Secondary endpoints include objective response rate, breast-conserving rate and invasive disease-free survival. Citation Format: Jin Zhang, Zhendong Shi, Jingjing Liu. An exploratory study of Trastuzumab Deruxtecan neoadjuvant therapy in HER2-positive or HER2-low early or locally advanced breast cancer after a poor response to neoadjuvant chemotherapy [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-18-04.

Abstract PS09-02: Event-free Survival by Residual Cancer Burden (RCB) and Intratumor HER2 Heterogeneity after Neoadjuvant T-DM1 and Pertuzumab for Early-stage HER2-positive Breast Cancer

Abstract Background: Intratumor HER2 heterogeneity (ITH-HER2) predicates resistance to targeted anti-HER2-based therapy, and understanding its impact on response to HER2-directed therapies is particularly important with regimens that rely solely on targeted anti-HER2 therapies without chemotherapy. Methods: To determine the effect of ITH-HER2 on response to therapy, we conducted a single-arm phase II study in which patients (pts) with centrally confirmed HER2+ early-stage breast cancer received six cycles of preoperative T-DM1 plus pertuzumab. Baseline image-guided biopsies allowed central pathology evaluation of ITH HER2, defined as an area with HER2 amplification in >5% but < 50% of tumor cells or a HER2-negative area by FISH. The study met its primary endpoint by demonstrating inferior pathologic complete response (pCR) measured by Residual Cancer Burden (RCB) in the subset of ITH-HER2 pts. Single-cell ERBB2 FISH analysis identified the fraction of ERBB2 nonamplified cells as a factor associated with therapeutic resistance (Metzger et al. Cancer Discovery 2021). Secondary endpoints included event-free survival (EFS), invasive disease-free survival (iDFS), and breast cancer-specific survival (BCSS) by ITH-HER2 status and RCB scores. Results: 163 pts were enrolled and received treatment in the study from Jan 2015 to Jan 2018. Central pathology evaluation of HER2 heterogeneity was successful in 96% (157/163) of cases, with 16 classified as ITH-HER2. RCB-0 or -I rate in the ITH-HER2 vs. not was (25% v. 67%, OR = 5.6, p = 0.002). Median follow-up, including all treated pts (n =163), was 65.4 months (IQR, 60.3-76.6). The 5yr EFS, iDFS, and BCSS were 91% [86.5% - 95.6%], 89.4% [84.5% - 94.5%], and 96% [92.9% - 99.2%], respectively. ITH-HER2 was associated with numerically inferior outcomes for EFS, iDFS, and BCSS (Table 1). The subset of pts with non-ITH-HER2 at baseline (n= 141) and RCB-0 or -I (n = 95/141, 67%) had a 5-yr IDFS of 94.2% [89.3% - 99.3%]. A sensitivity analysis describing survival outcomes by chemotherapy use in the adjuvant setting will be presented at the meeting, along with translational research results evaluating the association of HER2DX assay with pCR and survival outcomes. Conclusions: The inferior pCR rates among cases classified as ITH-HER2 translated into numerically inferior outcomes for both EFS and iDFS. The number of events is small; therefore, our results are exploratory. Selecting pts whose tumors lack ITH-HER2 can increase the chances of achieving RCB 0/I with neoadjuvant TDM1 + pertuzumab. Neoadjuvant TDM1 + pertuzumab, followed by adjuvant HER2-directed therapy without classic chemotherapy agents, could represent an optimal regimen for non-ITH-HER2 pts experiencing RCB 0/I at the time of surgery and deserves further study. Table 1. 5-year survival estimates by ITH-HER2 Citation Format: Otto Metzger, Se Eun Kim, Nabihah Tayob, Giuseppe Viale, Denise Yardley, Aleix Prat, Vandana Abramson, Laura Spring, Adrienne Waks, Eileen Wrabel, Michelle DeMeo, Aditya Bardia, Patrizia Dell'Orto, Leila Russo, Tari King, Franziska Michor, Eric Winer, Kornelia Polyak, Sara Tolaney, Ian Krop. Event-free Survival by Residual Cancer Burden (RCB) and Intratumor HER2 Heterogeneity after Neoadjuvant T-DM1 and Pertuzumab for Early-stage HER2-positive Breast Cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PS09-02.

Abstract PO1-01-03: Pathological response according to early metabolic remission in an interim FDG-PET scan and to tumor infiltrating lymphocytes - A secondary analysis of the phase II trial ABCSG 52/ATHENE investigating atezolizumab in early HER2+ BC

Abstract Background: ABCSG-52/ATHENE investigated a neoadjuvant chemotherapy de-escalation/immunotherapy escalation approach with trastuzumab, pertuzumab, atezolizumab and epirubicin for early-stage HER2-positive breast cancer. The pathological complete response rate (pCR; ypT0/Tis, ypN0) - the primary endpoint of the trial - was 60.3% (95% CI 47.5% - 71.9%), and was higher than the predefined threshold for positivity (≥ 40%). Interestingly, higher pCR rates were observed in PD-L1 immune cell (IC) negative tumors (pCR 69.2%) as compared to PD-L1 IC positive tumors (pCR 55.2%). No new safety concerns were observed. Primary outcome data were reported at the ESMO Breast Cancer Conference 2023. Here, we present the correlation of pathological outcome according to early metabolic response in an interim fluorodeoxyglucose F18 positron emission tomography (FDG-PET) scan, and according to stromal tumor infiltrating lymphocytes (TILs) at baseline. Methods: Patients (pts) with previously untreated, histologically confirmed HER2-positive early breast cancer (EBC; clinical prognostic stage cT1c-4a-d, N0–3, M0) were randomized 1:1 to two 3-weekly cycles of a chemotherapy-free induction phase (Part 1) with trastuzumab and pertuzumab (TP) plus 1200 mg atezolizumab (TP+A), or TP alone. Subsequently, all pts received 4 cycles of TP+A in combination with epirubicin 90 mg/m² (Part 2). Randomization was stratified according to baseline TILs (< 5% vs ≥ 5%), hormone receptor status (positive vs. negative), and prognostic stage (≤ IIA vs. ≥ IIB; AJCC v.8.0). An FDG-PET assessment was performed at baseline and after 2 cycles of study treatment. According to PERCIST, early metabolic responses were classified as metabolic complete response (mCR) and metabolic partial response (mPR) and association with outcome was tested with Fisher’s exact test. TIL assessment in pretreatment biopsy specimen were performed according to the recommendations from the International TILs Working Group. Lymphocytic predominant phenotype was defined as a TIL proportion of ≥ 50%. Correlation of TILs and pCR was modeled with logistic regression. Results: Overall, 58 pts were randomized to TP-A (n=29) or TP (n=29) at 9 sites. In 45 patients, a protocol predefined PERCIST assessment was available. An early mCR was achieved in 14 pts (n=14/45, 31.1%): 5 pts (n=5/21, 23.8%) in the TP group and 9 pts (n=9/24, 37.5%) in the TP-A group. Pts with and without an early mCR achieved a pCR in 92.9% (n=13/14) and 54.8% (n=17/31) of cases (p=0.016), respectively. An early mCR/mPR was achieved in 37 pts (n=37/45, 82.2%). Pts with and without an early mCR/mPR achieved a Residual Cancer Burden (RCB) class 0 or I in 89.2% (n=33/37) and 50.0% (n=4/8) of cases (p=0.024), respectively. The mean stromal TIL proportion was 23.9% in the overall population, with 22.8% in TP group and 25.0% in TP-A group. A lymphocytic predominant phenotype was seen in 10.3% of pts treated in the TP group, and 17.2% of pts treated in the TP-A group. No association between TIL proportion at baseline and pCR could be detected (OR for a 10%-point increase = 1.02, 95% CI 0.78-1.34). A moderate positive correlation between numeric values of TILs and PD-L1 ICs was observed (spearman r=0.57, P< 0.0001). Exploratory correlation analyses of PD-L1 status, TIL proportion and metabolic responses in interim FDG-PET scans will be presented at the meeting. Conclusions: In ABCSG-52, chemotherapy de-escalation with intensified immunotherapy was effective and safe. Early metabolic response assessment was feasible and predicted pathologic response; therefore, incorporation of interim FDG-PET results into de-escalation trials merits further investigation. In contrast to regimens without immune-checkpoint inhibitors, TIL proportion at baseline did not correlate with pathological outcome. Funding: Provision of IMP and financial support by Roche Austria GmbH Citation Format: Gabriel Rinnerthaler, Daniel Egle, Rupert Bartsch, Clemens Schmitt, Andreas Petzer, Marija Balic, Edgar Petru, Ursula Denison, Christian F. Singer, Vesna Bjelic-Radisic, Simon Gampenrieder, Michael Knauer, Karl Sotlar, Christine Brunner, Florian Posch, Dominik Hlauschek, Lidija Sölkner, Zsuzsanna Bago-Horvath, Martin Filipits, Manuela Gili, Michael Gnant, Richard Greil. Pathological response according to early metabolic remission in an interim FDG-PET scan and to tumor infiltrating lymphocytes - A secondary analysis of the phase II trial ABCSG 52/ATHENE investigating atezolizumab in early HER2+ BC [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-01-03.

Efficacy and safety of Trastuzumab Emtansine in treating human epidermal growth factor receptor 2-positive metastatic breast cancer in Chinese population: a real-world multicenter study.

Trastuzumab emtansine (T-DM1) has been approved worldwide for treating metastatic breast cancer (mBC) in patients who have received first-line therapy, shown disease progression, and are human epidermal growth factor receptor 2 (HER2)-positive. T-DM1 received approval in China to treat early-stage breast cancer (BC) in 2020 and for mBC in 2021. In March 2023, T-DM1 was included in medical insurance coverage, significantly expanding the eligible population. This post-marketing observational study aimed to assess the safety and effectiveness of T-DM1 in real-world clinical practice in China. This study enrolled 31 individuals with HER2-positive early-stage BC and 70 individuals with HER2-positive advanced BC from 8 study centers in Shandong Province, China. The T-DM1 dosage was 3.6 mg/kg injected intravenously every 3 weeks until the disease advanced or the drug toxicity became uncontrollable, whichever occurred earlier. Additionally, efficacy and safety information on T-DM1 were collected. During the 7-month follow-up period, no recurrence or metastases were observed in patients who had early-stage BC. The disease control rate was 31.43% (22/70) in patients with advanced BC. The most common adverse effect of T-DM1 was thrombocytopenia, with an incidence of 69.31% (70/101), and the probability of Grade ≥ 3 thrombocytopenia was 11.88% (12/101). This real-world study demonstrated that T-DM1 had good efficacy and was well tolerated by both HER2-positive early-stage BC and mBC patients.

Perspectives on shorter durations of anti-HER2 therapy in early-stage HER2-positive breast cancer: a patient survey.

Despite previous studies proposing shorter durations of anti-HER2 therapy for selected patients with HER2-positive early breast cancer (EBC), 12-months remains standard of care. A survey was performed to assess patient perspectives and willingness to participate in studies evaluating shorter durations of anti-HER2 therapy. Patients with HER2-positive EBC completing or having previously completed anti-HER2 therapy, were recruited by healthcare professionals at The Ottawa Hospital Cancer Centre to participate in an anonymous online survey. The primary objective was to learn about patients' perspectives on shorter durations (less than 12-months) of anti-HER2 therapy. Secondary objectives were to explore patients' interest in clinical trials of shorter durations of anti-HER2 therapy and the degree of increased breast cancer risk they would accept with a shorter treatment duration. Responses were received from 94 eligible patients. Most patients received Trastuzumab alone (78%, 73/94), while 13% (12/94) received trastuzumab and pertuzumab. Side effects were experienced by 52% (46/89), the most common being; fatigue (61%, 28/46), myalgia (37%, 17/46), and diarrhea (24%, 11/46). Most patients (88%, 78/89) did not find treatment bothersome. Regarding perspectives on shorter durations of anti-HER2 therapy, most (79%, 74/94) respondents stated they would agree to less treatment if it were possible to receive fewer treatments with the same cancer benefits. 56% of patients were interested in clinical trials, however, about half stated they would not be accepting of any increase in breast cancer recurrence risk. Trials to investigate who can safely and effectively be treated with shorter durations of anti-HER2 therapy are needed. This study provides important insights to patients' perspectives on shorter durations of anti-HER2 treatment, and their concerns regarding potential increased cancer risk with less treatment.

Management of early-stage HER2-positive breast cancer and attitudes towards HER2DX test in Spain: insights from a nationwide survey

PurposeThis study aimed to investigate the current therapeutic management of patients with early-stage HER2-positive (HER2+) breast cancer in Spain, while also exploring the perceptions surrounding HER2DX in terms of its credibility, clinical relevance, and impact on therapeutic decision-making. Understanding these aspects is crucial for optimizing treatment strategies and enhancing patient outcomes in the context of HER2+ breast cancer.MethodsAn online questionnaire was conducted by an independent third-party between April and May 2022 across 70 medical oncologists highly specialized in breast cancer management in Spain. The survey included 37 questions regarding treatment decision making in HER2+ early breast cancer.ResultsThe management of patients with HER2+ early breast cancer exhibited a high degree of heterogeneity. Among the interviewed oncologists, 53% would recommend upfront surgery for node negative tumors measuring 1 cm or less. Interestingly, 69% and 56% of interviewers were open to deescalate the duration of adjuvant trastuzumab in pT1a and pT1b N0 tumors, respectively. Certain clinicopathological characteristics, such as high grade, high Ki-67, and young age, influenced the decision to prescribe neoadjuvant treatment for patients with clinical stage 1 disease. In cases where neoadjuvant treatment was prescribed for cT1-2 N0 tumors, there was a wide variation in the choice of chemotherapeutic and anti-HER2 regimens. Regarding the use of adjuvant trastuzumab emtansine (T-DM1) in patients with residual disease after neoadjuvant therapy, there was diversity in practice, and a common concern emerged that T-DM1 might be overtreating some patients. HER2DX, as a diagnostic tool, was deemed trustworthy, and the reported scores were considered clinically useful. However, 86% of interviewees believed that a prospective trial was necessary before fully integrating the test into routine clinical practice.ConclusionIn the context of early-stage HER2+ breast cancer in Spain, a notable diversity in therapeutic approaches was observed. The majority of interviewed medical oncologists acknowledged HER2DX as a clinically valuable test for specific patients, in line with the 2022 SEOM-GEICAM-SOLTI clinical guidelines for early-stage breast cancer. To facilitate the full integration of HER2DX into clinical guidelines, conducting prospective studies to further validate its efficacy and utility was recommended.