Rocque, Gabrielle B.

PURPOSE EA1181 (ClinicalTrials.gov identifier: NCT04266249 ) is a single-arm trial evaluating neoadjuvant taxane, trastuzumab, and pertuzumab (THP) in patients with clinical stage II/IIIa human epidermal growth factor receptor 2 (HER2)–positive breast cancer. This report focuses on the secondary end points of pathologic complete response (pCR) rates and associated factors. The primary end point—3-year recurrence-free survival among patients achieving a pCR (ypT0/Tis, ypN0)—will be reported when data mature. METHODS Patients received four cycles of trastuzumab and pertuzumab (HP) with either once per week paclitaxel (12 weeks) or docetaxel (every 3 weeks for four cycles), followed by surgery. Clinicopathologic characteristics were assessed in all patients. The HER2DX pCR score was determined using diagnostic biopsy samples in a representative subset. Logistic regression models identified factors associated with pCR. RESULTS A total of 2,175 patients were enrolled (781 HER2+/estrogen receptor‑negative [ER–]; 1,394 HER2+/ER+). Of 2,141 patients who initiated THP, the overall pCR rate was 43.8%: 63.7% in HER2+/ER– and 32.4% in HER2+/ER+ tumors. Higher pCR rates were observed in tumors that were ER-negative or low ER expressing, progesterone receptor-negative or low expressing, HER2 immunohistochemistry (IHC) 3+, and in patients treated with once per week paclitaxel. T3 disease was associated with a lower pCR rate in HER2+/ER– tumors; otherwise, tumor (T) and nodal (N) stage did not significantly affect pCR. Among 569 patients assessed for HER2DX pCR scores, a high score was independently associated with higher pCR rates, after adjustment for clinicopathologic variables. CONCLUSION Neoadjuvant THP achieved pCR in nearly two-thirds of patients with HER2+/ER– and one third with HER2+/ER+ breast cancer. Low hormone receptor expression, HER2 IHC 3+ status, once per week paclitaxel use, and a high HER2DX pCR score were independent predictors of pCR. These findings should help optimize risk stratification and treatment personalization for patients with HER2-positive breast cancer.

603 Background: Accurate prediction of pathologic complete response (pCR) after preoperative therapy for HER2-positive (HER2+) breast cancer can help triage patients to immediate surgery vs additional preoperative therapy. Pre-surgery (i.e., after neoadjuvant therapy) imaging studies may help estimate the likelihood of pCR. In EA1181, patients (pts) with stage II-IIIA HER2+ breast cancer received four cycles of preoperative taxane, trastuzumab, and pertuzumab (THP×4). Pre-surgery imaging was required, though the specific imaging modality was not mandated. Here, we report the accuracy of pre-surgery breast MRI to predict pCR (ypT0/Tis, ypN0). Methods: Among 2,141 pts treated with THPx4, 1,378 had pre-surgery breast MRI and were representative of the overall cohort, although T3 tumors were more common (16% vs 9%). MRI reports were available for 1,351 pts; all reports were centrally reviewed and classified as radiologic complete response (rCR; no residual tumor enhancement and normalization of lymph nodes, if applicable) or radiologic residual disease (rRD). Reports with indeterminate radiologic response were independently reviewed by two study radiologists blinded to pathology outcomes. Among pts with rCR who had pathologic residual disease (pRD), we also assessed the extent of residual disease by residual cancer burden (RCB) score. Among pts with rRD who had a pCR, we determined the proportion who only had residual ductal carcinoma in situ (DCIS). Results: See Table. Conclusions: After neoadjuvant therapy, preoperative MRI accurately predicted pCR in 86% of patients with HER2+/ER− disease and may help identify patients who can proceed directly to surgery. MRI is insufficient to predict pCR for pts with HER2+/ER+ disease, as only 55% with complete response on MRI had a pCR at surgery. A pre-surgery MRI that indicated residual disease was accurate in 80% of pts with HER2+/ER+ disease, but in only 45% of pts with HER2+/ER- cancer. Accurately predicting residual disease after THPx4 allows for consideration of additional therapy that may increase the chance of pCR. Combining imaging like MRI with other biomarkers, such as tissue-based markers or circulating tumor DNA, may improve prediction of pCR and facilitate personalization of treatment decisions in HER2+ breast cancer. All pts with pre-surgery MRI (n=1351)pCR rate overall in this cohort = 47% MRI result Pathology pCR pRD rCR 70.6% (341/483) 29.4%(142/483) 78% had RCB1 rRD 34%(295/868) 21% of 295 had DCIS only 66.01% (573/868) ER- (n=589)*Overall pCR rate in ER- subset = 68% MRI result Pathology pCR pRD rCR 86.1% (205/238) 13.9% (33/238) 85% had RCB1 rRD 55.3% (194/351) 19% of 194 had only DCIS 44.7% (157/351) ER+ (n= 762)*Overall pCR rate in ER+ subset = 31% MRI result Pathology pCR pRD rCR 55.5% (136/245) 44.5% (109/245) 76% had RCB1 rRD 19.5% (101/517) 26% of 101 had only DCIS 80.5% (416/517)

1056 Background: Resistance to HER2-directed therapies remains a major challenge in HER2-positiveMBC. In preclinical models, HER2+ tumors overexpress poly (ADP-ribose) polymerase (PARP), and PARP inhibition induces apoptosis through NF-κB suppression even in the absence of pathogenic mutations in BRCA 1/2 . We evaluated the safety, efficacy, and translational correlates of niraparib combined with trastuzumab in patients (pts) with refractory HER2+ MBC. Methods: This open-label Phase 1b/2 trial (NCT03368729) enrolled pts with HER2+ MBC (IHC 3+ and/or FISH amplified), measurable disease, LVEF ≥50%, and progression on ≥1 prior HER2-targeted therapy; stable CNS disease was allowed. Pts with germline BRCA1/2 mutations or prior PARP inhibitor exposure were excluded. Niraparib 300 mg orally was administered on Days 1–21 of a 21-day cycle with trastuzumab 6 mg/kg IV every 3 weeks (loading dose 8 mg/kg on cycle 1). The Phase 2 portion used a Gehan/Simon two-stage design with early stopping for futility (P0=24%); ≥1 response among the first 20 patients triggered expansion to 40 patients. ORR was assessed by RECIST v1.1, meeting the primary endpoint and allowing response rate estimation with <7% standard error and a two-sided 95% exact CI width of 0.28. Gene expression profiling of paired tumor tissue and peripheral blood mononuclear cells (PBMCs) was performed using the NanoString nCounter Tumor Signaling 360 panel at pretreatment compared to cycle 2. Results: Forty-six pts were enrolled (9/2019–2/2025); 41 were evaluable for response. Pts were heavily pretreated (median 3 prior regimens), including trastuzumab deruxtecan in 22 pts; 33% had brain metastases. Treatment-related adverse events were predominantly grade 1–2 and manageable. Clinical benefit rate (CBR) was 44% (18/41) including 1 complete response, 2 partial responses, and 15 stable disease. Eleven patients achieved disease control ≥ 6 months; 1 patient remained on treatment at data cutoff. Tumor profiling revealed enrichment of a B-cell–driven tertiary lymphoid structure signature with reduced hypoxia signaling in responders. Matched PBMC analyses demonstrated coordinated downregulation of interferon signaling, DNA damage response, metabolic activation, angiogenesis, and resistance pathways in clinical responders, whereas non-responders retained signatures of chronic stress and immune exhaustion. Conclusions: Niraparib plus trastuzumab demonstrated a favorable safety profile and durable clinical benefit in heavily pretreated HER2+ MBC. Integrated tumor and blood-based analyses identify immune-organized tumor microenvironments and systemic immune normalization as key correlates of prolonged response, supporting further investigation of PARP inhibition strategies. Clinical trial information: NCT03368729 .

Abstract Background: The association of TILs with pathologic complete response (pCR) and survival in HER2+ breast cancer is not well established with several prior studies showing inconsistent results. In this secondary analysis of EA1181, we evaluated the association between stromal TILs (sTILs) and pCR rates. Methods: EA1181 (NCT04266249) enrolled patients (pts) with anatomic clinical stage II/III HER2+ breast cancer who preoperatively received 4 cycles of trastuzumab and pertuzumab with 12 weeks of paclitaxel or docetaxel q3w x 4 (THP), followed by surgery. sTILs density was assessed on full-face hematoxylin and eosin (H&E)-stained tumor biopsy sections. sTILs scores were analyzed per protocol as a continuous variable (every 10% increment) and as a categorical variable (&lt;10% vs 10-60% vs &gt;60% as per Denkert et al, 2018), and also with an exploratory 30% cutoff commonly used in TNBC. Cox proportional hazards models were used to examine the association between sTILs and pCR, adjusting for available baseline factors. The associations between sTILs (by category) and clinicopathologic characteristics were examined using Fishers’ exact test. Results: Among 2141 pts with HER2+ BC treated on EA1181, H&E slides were available for 1328 (62%). The study population evaluated for sTILs was comparable to the overall population. pCR rates were 44.5% overall, 64% for HER2+/ER- and 33% for HER2+/ER+ disease. sTILs distribution was: 623 (47%) &lt;10%, 698 (52%) 10-60%, and 7 (0.5%) &gt;60%, which led us to merge the latter two groups (705 [53%] had ≥10% sTILs). In univariable and multivariable analyses, increasing sTILs (as a continuous variable) were associated with increasing pCR rates in both HER2+/ER+ and HER2+/ER- disease (p&lt;0.001; Table). sTILs analyzed as a categorical variable (&lt;10% vs ≥10%) were significantly associated with pCR for all patients (combined) and for those with HER2+/ER+ disease. In exploratory analysis using a cutoff of &lt;30% vs ≥30% sTILs, an association with pCR was also seen in univariable analysis for both HER2+/ER+ disease (p&lt;0.001) and HER2+/ER- disease (p=0.045), though in multivariable analysis with clinical factors, sTILs &gt;30% remained a significant predictor for pCR only in HER2+/ER+ disease. Additional exploratory analysis with other molecular biomarkers, intrinsic subtypes, and immune signatures will be presented. Conclusion: sTILs were associated with pCR after THP, further supporting the important role of immune mechanisms in HER2+ breast cancer, and highlighting a potentially robust predictive tool to assess pathologic response. Baseline sTILs could potentially inform the preoperative design of future trials of therapy optimalization. Association of baseline sTILs with recurrence free survival in EA1181 will be reported in the future. Citation Format: S. S. Badve, F. Zhao, N. Tung, Y. Gokmen-Polar, C. C. O'Sullivan, A. Prat, E. P. Winer, J. L. Wright, A. Recht, A. C. Weiss, J. A. Tjoe, S. M. Feldman, G. B. Rocque, M. Smith, N. Unni, S. Sardesai, S. Tang, S. Modi, W. J. Irvin, P. Villagrassa, C. Battelli, A. K. Krie, N. Bagegni, M. A. George, M. L. Telli, V. F. Borges, N. D’Abreo, P. Shah, K. D. Miller, A. H. Partridge, L. A. Carey, A. M. DeMichele, A. C. Wolff, ECOG-ACRIN.Tumor infiltrating lymphocytes (TILs) and pathologic complete response (pCR) in stage II/III HER2+ breast cancer treated with taxane, trastuzumab, and pertuzumab (THP): secondary results from the ECOG-ACRIN EA1181/CompassHER2 pCR trial [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr GS1-04.

501 Background: EA1181 (NCT04266249) is a single-arm trial of neoadjuvant THP for patients with clinical anatomic stage II/III HER2+ breast cancer; patients with cT4 or cN3 disease were excluded . Assessing the primary endpoint, 3-year recurrence-free survival in patients with a pCR (ypT0/Tis, ypN0), requires longer follow-up. Here, we present results for the secondary objective of pCR rate and its relation to clinicopathologic factors and the HER2DX pCR likelihood score (Reveal Genomics) derived from gene expression and clinical features. Methods: Patients received 4 cycles of trastuzumab and pertuzumab (HP) with weekly paclitaxel (12 weeks) or docetaxel (q3w x 4), followed by surgery. Clinicopathologic features were assessed for all patients and HER2DX pCR score (stratified by ER status) was determined using the diagnostic biopsy in a representative subset of study participants. Results: 2175 patients were enrolled. Median age was 55 years (range 22-88 years); 58% had clinical stage IIA, 33% stage IIB, and 9% stage III. 45% had nodal involvement (mostly cN1). 781 tumors were HER2+/ER- and 1394 HER2+/ER+ (locally tested ). 2141 patients started THP, for whom the pCR rate was 44% overall, 63.7% in HER2+/ER- and 32.4% in HER2+/ER+ tumors. Disease progressed during THP in 16 patients (0.7%). The pCR rate varied inversely to the proportion of cells staining for ER among patients with HER2+/ER+ breast cancer: 1-10%+, 62.5%; 11-69%, 51.6%; ≥70%, 22.5% (p <0.001). The pCR rate was significantly associated with higher grade, especially in HER2+/ER+ disease. T and N stage did not significantly affect pCR rate. Among 569 patients assessed for the HER2DX pCR score, the pCR rate was significantly greater for patients with a higher vs lower score, regardless of ER status (Table). Further correlations and interactions will be presented. Conclusions: Neoadjuvant THP resulted in pCR in nearly two-thirds of pts with clinical stage II/III HER2+/ER- and in one-third with HER2+/ER+ breast cancer. There was no association with clinical stage. Lower ER expression and higher grade were associated with higher pCR rates. The HER2DX pCR score was a significant predictor of pCR, regardless of ER status. Clinical trial information: NCT04266249 . All Participants HER2+/ER- HER2+/ER+ # patients enrolled pCR rate (95% CI) # patients enrolled pCR rate (95% CI) # patients enrolled pCR rate (95% CI) Evaluable Cohort 2141 44%(42-46%) 774 64%(60-67%) 1367 32%(30-35%) HER2DX Cohort 569 48%(44- 52%) 230 69% (63-75%) 339 34%(29-39%) HER2DX pCR-high score 182 (32%) 68%(60-74%) 147 (64%) 70% (62-77%) 36 (11%) 58%(41-74%) HER2DX pCR-medium score 161 (28%) 67% (59- 74%) 70 (30%) 74%(62- 84%) 89 (26%) 61%(50-71%) HER2DX pCR-low score 226 (40%) 19%(14- 25%) 13 (6%) 31%(9-61%) 214 (63%) 18%(13-24%) P-value HER2DX score <0.001 0.010 <0.001

AbstractBackgroundBreast cancer patients experienced heightened anxiety during the pandemic. Also, modifications to clinical trial activities allowing for virtual platforms, local assessments, and greater flexibility were introduced to facilitate participation. We sought to evaluate the association between pandemic‐related anxiety and willingness to participate in trials and how pandemic‐era modifications to trial activities affect the decision to participate.MethodsWe conducted an online survey from August to September, 2021 of patients with breast cancer assessing pandemic‐related anxiety; clinical trials knowledge and attitudes; willingness to participate during and before the pandemic; and how each modification affects the decision to participate. Fisher's exact tests evaluated differences in proportions and two‐sample t‐tests evaluated differences in means. The association of pandemic‐related anxiety with a decline in willingness to participate during compared to prior to the pandemic was modeled using logistic regression.ResultsAmong 385 respondents who completed the survey, 81% reported moderate–severe pandemic‐related anxiety. Mean willingness to participate in a trial was lower during the pandemic than prior [2.97 (SD 1.17) vs. 3.10 (SD 1.09), (p < 0.001)]. Severe anxiety was associated with higher odds of diminished willingness to participate during the pandemic compared to prior (OR 5.07). Each of the modifications, with the exception of opting out of research‐only blood tests, were endorsed by >50% of respondents as strategies that would increase their likelihood of deciding to participate.ConclusionsWhile pandemic‐related anxiety was associated with diminished willingness to participate in trials, the leading reasons for reluctance to consider trial participation were unrelated to the pandemic but included worries about not getting the best treatment, side effects, and delaying care. Patients view trial modifications favorably, supporting continuation of these modifications, as endorsed by the National Cancer Institute and others.

Abstract Background: Historically, less than 10% of adult patients with cancer enroll in clinical trials, however, enrollment dropped further at the onset of the COVID-19 pandemic. Barriers to trial participation during the pandemic have not been reported. As part of the TBCRC 057 survey on the impact of the pandemic on willingness to participate in breast cancer trials, we assessed reasons for reluctance to participate in trials during the pandemic. Methods: US residents who self-reported a breast cancer diagnosis were eligible to complete the online survey 8/6/21-9/30/21. Respondents indicated whether they were current trial participants and, if not, their willingness to consider participating in a trial during the pandemic using a 5-point scale (0-not at all willing to 4-definitely willing). Respondents who were not current trial participants and who were not “definitely willing” to consider participation during the pandemic were characterized as “reluctant” and asked to select reasons for their reluctance from a checklist. Pandemic-related anxiety was assessed on an 11-point scale (0-no anxiety to 10-worst anxiety possible). Respondents indicated how the option to conduct trial activities online would affect their decision to participate in a trial (much less likely, somewhat less likely, would not affect my decision, somewhat more likely, or much more likely). In exploratory analyses, we evaluated whether pandemic-related anxiety and favorable reactions towards opportunities to conduct trial activities online were associated with reluctance to consider trial participation during the pandemic due to fear of SARS-CoV-2 exposure. Means were compared with two sample t-tests and proportions with Fisher’s exact tests. Results: Of 385 survey respondents, 185 (48%) were characterized as reluctant to consider trial participation during the pandemic. Among these 185, median age was 55 (range 25-80), 85.7% were non-Hispanic White, 48.1% had metastatic disease and 44.2% received care at academic centers. Reasons for reluctance to consider trial participation during the pandemic cited by ≥15% of the 185 reluctant respondents are shown in the Table. Respondents who selected fear of exposure to SARS-CoV-2 as a reason for their reluctance to consider participating in a trial during the pandemic had higher mean pandemic-related anxiety (7.0 vs 5.2, p&lt; 0.001). These respondents were more likely to indicate telemedicine doctor visits (p=0.01), virtual consents (p=0.001) and online study questionnaires (p=0.001) would make them somewhat or much more likely to participate in trials than respondents who did not select fear of exposure to SARS-CoV-2 as a reason for their reluctance. Conclusions: Reasons for reluctance of patients with breast cancer to consider participation in clinical trials during the pandemic are multifactorial. Although concerns about safety and efficacy remain prominent, fear of exposure to SARS-CoV-2 drives unwillingness to participate in &gt;25% of reluctant patients. Trial accrual may benefit from incorporation of electronic activities when possible. Table Citation Format: Karen L. Smith, Carolyn Mead-Harvey, Gina L. Mazza, Albert E. Holler, Eileen Shinn, Elizabeth Frank, Michelle Melisko, Cyd Eaton, Jeannine M. Salamone, Teri Pollastro, Patricia Spears, Antonio C. Wolff, Gabrielle B. Rocque. Reasons for Reduced Willingness to Participate in Clinical Trials During the COVID-19 Pandemic: The Translational Breast Cancer Research Consortium (TBCRC) 057 Survey [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 P6-08-07.

97 Background: In order to maintain safety, clinical trial activities have been modified during the COVID-19 pandemic. As part of the TBCRC 057 survey, we assessed how pandemic-related modifications to trial activities affect breast cancer patients’ willingness to participate in clinical trials. Methods: US residents with breast cancer were eligible to complete the online survey 8/6/21 – 9/30/21. Respondents rated whether each of 11 modifications to clinical trial activities would affect their decision to participate in a trial during or after the pandemic. Items evaluated modifications that involved changing the location of trial activities to closer to home, switching trial activities to telemedicine and making the trial schedule more flexible and convenient. Response options were “much less likely to participate”, “somewhat less likely to participate”, “would not affect my decision whether or not to participate”, “somewhat more likely to participate” and “much more likely to participate”. Current trial participants were asked to consider how modifications would affect their decision to participate in another trial. Results are reported descriptively. Results: Among 385 respondents, median age was 52 (range 25-85), 88.6% were non-Hispanic White, 52.5% had metastatic disease, 93% were receiving active treatment, 48.6% received care at an academic center and 9.6% were current trial participants. Changing location of trial activities was viewed favorably, with 70.2%, 64.6% and 54.1% of respondents indicating they would be much or somewhat more likely to participate if they could complete trial blood tests, x-ray tests or doctor visits closer to home, respectively. Similarly, the option to complete trial activities electronically was viewed favorably, with 59.6%, 58.6% and 60.9% of respondents indicating they would be much or somewhat more likely to participate if they could complete trial doctor visits, consent and questionnaires via telemedicine, respectively. With regard to modifications to make the trial schedule more flexible and convenient, respondent feedback was also favorable. 71.4%, 67.7% and 82.4% of respondents indicated that requiring study site visits no more than once per 3 weeks, widening windows for trial activities and offering home delivery of oral study medications, respectively, would make them much or somewhat more likely to participate. Finally, 30.4% and 51.7% indicated that the flexibility to opt-out of research-only blood tests and biopsies, respectively, would make them much or somewhat more likely to participate. Conclusions: Patients view modifications to trial activities implemented during the pandemic favorably. Trials should be flexible and the option to conduct study activities close to home or electronically when possible should be maintained during the pandemic and beyond.

1564 Background: Enrollment in clinical trials has declined during the COVID-19 pandemic. Simultaneously, breast cancer patients have reported heightened anxiety. We assessed whether breast cancer patients’ anxiety about the pandemic affects their willingness to participate in trials. Methods: English or Spanish-speaking US residents with breast cancer were eligible to complete the online REDCap survey 8/6/21 – 9/30/21. Respondents rated their anxiety about the pandemic on an 11-point scale from 0 (no anxiety) to 10 (worst anxiety possible). Anxiety scores were categorized as no/mild (0-3), moderate (4-6) or severe (7-10). Knowledge about trials was assessed with 11 true/false items and attitudes toward trials with the Attitudes Toward Cancer Trials Scales - Cancer Treatment Subscale (ATCTS-CTS). Respondents rated their willingness to participate in a breast cancer clinical trial before and during the pandemic on 5-point scales from 0 (not at all willing) to 4 (definitely willing). Trial participants were considered “definitely willing.” Change in willingness to participate in trials during the pandemic compared to prior was defined as a binary outcome, "less willing" vs "no less willing." Means were compared via t-test and mean difference was tested via paired t-test. Multivariable logistic regression was used to model the association of anxiety and other factors with being less willing to participate in trials during compared to prior to the pandemic. Results: Among 385 respondents, median age was 52 (range 25-85), 271 (70%) were non-Hispanic White and 202 (53%) had metastatic disease. 154 (40%) received care at academic centers and 37 (10%) were current trial participants. Most rated their anxiety as moderate (43%) or severe (38%). Mean willingness to participate in a trial was lower during compared to prior to the pandemic (2.97 vs 3.10; p < 0.0001). Fifty (13%) respondents were less willing to participate in a trial during the pandemic compared to prior. After controlling for covariates, those with severe anxiety had 5.07 times odds of being less willing to participate during the pandemic compared to prior than those with no/mild anxiety (p = 0.01). For every 1-point increase in ATCTS-CTS score (indicating better attitude toward trials) there was a 3% decrease in the odds of being less willing to participate during the pandemic (p = 0.006). For every 1-point increase in the clinical trials knowledge score (indicating more knowledge) there was a 15% decrease in the odds of being less willing to participate during the pandemic (p = 0.02). Conclusions: Pandemic-related anxiety is common in breast cancer patients and is associated with being less willing to participate in trials during the pandemic compared to prior. Education about trials, including safety modifications implemented during the pandemic, may mitigate anxiety and improve willingness to participate.