Citations

Background Corticosteroid injections (CSIs) are widely employed for chronic pain. These injections include peripheral nerve blocks and trigger point injections, injections of large appendicular joints, the axial facet and sacroiliac joints, and the epidural space. These injections may be performed in patients who have been recently vaccinated or plan to be vaccinated. This multisociety multispecialty position statement aims to develop evidence-based statements and recommendations (SRs) on the safe interval between CSIs and COVID-19 and influenza vaccine administration. Methods Development of the position statement was approved by the American Society of Regional Anesthesia and Pain Medicine Board of Directors and several other societies that agreed to participate. The scope of the SRs was agreed on to include the efficacy of COVID-19 and influenza vaccines, adverse events related to the CSIs, specifically the effect of CSIs on the hypothalamic–pituitary axis, incidence of COVID-19 in patients who had CSIs during the pandemic, incidence of influenza in patients who had CSIs during the influenza season, and recommend a reasonable interval between CSIs and COVID-19 and influenza vaccination 20 mg/day of prednisone s. Experts were assigned topics to perform a comprehensive literature review and draft SRs, which were refined and voted for consensus (≥75% agreement) using a modified Delphi process. A modified version of the US Preventive Services Task Force grading of evidence and strength of recommendation was followed. Results All SRs were approved by all participants after four rounds of discussion. The Practice Guidelines Committees and Boards of Directors of the participating societies also approved all SRs. If a vaccine has been recently administered or planned, then for non-urgent indications, the CSI should be offered at least 1 week before or after vaccine administration. For healthy patient(s), CSI, or vaccine administration may be performed without a 7-day interval after informed discussion with the patient and consent regarding the risk of blunted vaccine efficacy. For non-healthy patients, shared decision-making should include discussion of diminished vaccine effectiveness and the possibility of influenza or COVID-19 infection. Conclusions In this position statement, we provide recommendations on the optimal timing between CSIs and COVID-19 or influenza vaccine.

Abstract Patients with multiple myeloma have an elevated risk of severe complications from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2; COVID-19) infection. To demonstrate proof of concept for a pandemic preparedness and response network, the American Society of Hematology Research Collaborative Multiple Myeloma Program developed a prospective, decentralized study within a site-based provider network. In the COVID-19 outcomes in myeloma and the impact of vaccines (COSMIC) study, patients provided consent, permitted electronic health record data collection, completed patient-reported outcomes at baseline, day 30, and day 180 through an electronic study portal, and were compensated for participation. Clinicians at participating sites facilitated study recruitment and shared best practices monthly to accelerate study execution. The COSMIC study rapidly consented 201 patients from 8 participating sites over 4 months (22 January 2024 through 17 May 2024). Consented participants were 30 to 93 years old, with a median age of 67; 46% were female, 69% were non-Hispanic White, 17% were non-Hispanic Black, and 8% were Hispanic/Latino. Patient-reported data completion was 97% at baseline, 81% at 1 month, and 79% at 6 months. At baseline, 55% of patients reported a history of COVID-19 infection and had received a median of 4 SARS-CoV-2 vaccines. For all patients, there were an additional 18 COVID-19 infections and 57 vaccines received during the 6-month observation period. There were no significant differences in health-related quality of life over time or by history of COVID-19 infection. COSMIC demonstrates the feasibility of an innovative evidence generation strategy to drive rapid accrual of patients to address an evolving area of need. This trial was registered at www.clinicaltrials.gov as #NCT05831787.

In this 5-year follow-up from the CheckMate 743 study in patients with unresectable pleural mesothelioma (PM), we evaluated updated efficacy and safety outcomes and biomarkers and performed treatment-switching analyses with first-line nivolumab plus ipilimumab versus chemotherapy. With a median follow-up of 66.8 months, nivolumab plus ipilimumab demonstrated continued overall survival (OS) benefit versus chemotherapy in all randomly assigned patients (5-year OS rates, 14% v 6%; hazard ratio [HR], 0.74 [95% CI, 0.62 to 0.88]); similar benefit was observed regardless of tumor histology. Of biomarker-evaluable patients treated with nivolumab plus ipilimumab (n = 242), high baseline monocytic myeloid-derived suppressor cell (M-MDSC) levels correlated with worse OS versus low M-MDSC levels (HR, 1.25 [95% CI, 1.09 to 1.43]). After adjusting for 24% of patients in the chemotherapy arm who received subsequent immunotherapy, nivolumab plus ipilimumab demonstrated continued OS benefit versus chemotherapy (HR, 0.64 [95% CI, 0.53 to 0.78]). No new safety signals were observed. These results demonstrate long-term, durable clinical benefit with nivolumab plus ipilimumab versus chemotherapy, which continued to be preserved even after treatment-switching adjustment in the chemotherapy arm. Exploratory analyses suggested greater benefit with nivolumab plus ipilimumab in the low M-MDSC subgroup. These results further support first-line nivolumab plus ipilimumab as standard of care for unresectable PM.

Abstract Introduction Cancer clinical trials have historically faced challenges in achieving fully representative trial population, particularly in terms of including patients from diverse ethnic and racial groups, those with low socioeconomic status, and those living in rural regions. This has contributed to inequities in access to novel therapeutic options. Background The I-SPY adaptive platform trials have prioritized diversity since inception, consistently enrolling in >10% of trial patients being Black and/or Hispanic individuals. The majority of participating institutions in the I-SPY 2.2 study are academic or large well-resourced health systems. In 2023, the I-SPY ACCESS (Achieving Cancer Clinical Trial Equity in Socioeconomically Diverse Sites) Initiative was launched to enhance representation by engaging and involving nontraditional trial sites- such as safety-net hospitals, community cancer centers, and rural cancer centers- that serve historically excluded patient populations. Methods The I-SPY ACCESS Initiative offers customized and personalized tailored support to under-resourced sites. This includes comprehensive feasibility and readiness assessments, onboarding guidance, enhanced site-specific training, centralized institutional review board (IRB) navigation, site peer mentorship, and educational materials for both patient and provider. Additionally, patients gain access to I-SPY advocate peer trial navigators. Sites are provided culturally responsive patient education tools- including multilingual brochures, a dedicated patient website, and content co-developed with community partners. A Clinical Trial Navigator supports both patients and sites, helping to locate logistical, social, and trial specific resources.Tools such as virtual Clinical Research Coordinators (vCRC's) and OneSource technology are deployed strategically based on assessed site need and resource availability. OneSource is an innovative platform that enables direct extraction of clinical data from electronic health records into trial databases, reducing site workload and improving data quality. Funding models are currently being explored to extend OneSource and vCRC services across more ACCESS sites. In the future, there are plans to pilot financial navigation services and integrative care resources for all patients enrolled in I-SPY with particular focus on those enrolled at ACCESS sites. Results and Progress As of June 2025, seven sites have been assessed as ACCESS sites for I-SPY 2.2, with two sites having successfully completed activation and currently enrolling participants. Beginning in mid-2024, one DCIS RECAST ACCESS site has been activated and 11 additional sites are in the onboarding process. The modest pace of I-SPY 2.2 activation reflects the complexity and operational demands associated with resource-intensive platform trial. In contrast, the DCIS RECAST protocol was designed with a lower burden, facilitating easier implementation by under-resourced sites, reflected by increased interest in the study among ACCESS sites. The ACCESS framework is being explored for potential future application in the Pre I-SPY Phase 1 platform trial, particularly considering the historical underrepresentation of such sites in the early-phase clinical research. Conclusion and Future Goals The I-SPY ACCESS initiative demonstrates that investing in thoughtful, innovative, and effective means for trial delivery, as well as incorporating community-based support, can strengthen representation in complex, adaptive breast cancer trials. The initiative offers a flexible, equity-driven framework that is impactful now and scalable for future innovation in oncology research. Citation Format: S. L. Horton, D. A. Idossa, K. C. Hewitt, J. Perlmutter, L. Van't Veer, N. Hylton, A. Borowsky, F. Symmans, D. Yee, C. Yau, P. Pohlmann, J. Boughey, L. Esserman. Expanding Diversity through Innovation: Development of the I-SPY ACCESS Initiative for the I-SPY2.2 and DCIS RECAST Clinical Trials [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 PS4-09-08.

Abstract Background: The Breast Cancer Index (BCI) is clinically validated to stratify patients with hormone receptor-positive (HR+), early-stage BC based on the risk of overall (0-10 years [y]) and late (5-10 y) distant recurrence (DR) with N0/N1 lymph node involvement. Validation of BCI in patients with HR+ HER2+ BC has been limited, especially in patients treated with adjuvant trastuzumab-based chemotherapy. The HOXB13 and IL17BR genes constitute the predictive component of BCI and are known to exhibit an ER-dependent correlation pattern with HER2. We evaluated the prognostic performance of BCI in patients with HR+ HER2+ disease enrolled in the NCCTG N9831 (Alliance) trial treated with the combination of chemotherapy and trastuzumab. Methods: All available tumor specimens from patients with HR+ HER2+ N0/N1 BC in arms B (sequential trastuzumab) and C (concurrent trastuzumab) of the trial were included. BCI testing was performed blinded to clinical outcomes. The primary endpoint was distant recurrence-free interval (DRFI). BCI (N0) and BCIN+ (N1) risk groups were calculated based on prespecified cut points. Kaplan-Meier analysis and log-rank testing were used to assess the prognostic significance of BCI/BCIN+ risk groups based on DR. Cox proportional hazard models with and without clinical covariates were used to estimate hazard ratios (HRs), and the associated 95% confidence intervals (CIs). Results: A total of 454 HR+ patients (234 arm B, 220 arm C), including 69 N0 and 385 N1 patients, were analyzed (median age was 47 y, 85% N1, 55% T2, 63% G3). BCIN+ scores were available for 378 of the 385 N1 patients due to missing tumor grade for 7 patients. The median follow-up was 12.7 years. In the overall cohort, BCI/BCIN+ stratified 51 (11%), 24 (5%) and 372 (83%) patients as low-, intermediate- and high-risk with 10-y DRFI rates of 96% (95% CI: 84-99%), 100% (100-100%) and 89% (86-92%), respectively. Since the low and intermediate risk groups had few patients and a similar risk of 10-y DRFI, they are combined into a single low-risk group hereafter. Thus, for overall 10-y DR, 75 (17%) and 372 (83%) of patients were classified by BCI/BCIN+ as low and high risk with 10-y DRFI rates of 97% (95% CI: 89-99%) and 89% (95% CI: 86-92%), respectively (HR=4.50, 95% CI: 1.09-18.61; p = 0.038). BCI/BCIN+ remained statistically significant in the multivariable analysis, adjusting for age, treatment, and nodal status (HR=7.54, 95% CI: 1.34-42.64; p = 0.022). For 69 N0 patients, BCI stratified 54 (78%) and 15 (22%) patients as low and high risk with 10-y DRFI rates of 100% (95% CI, 100-100%) and 77% (95% CI, 44-92%), respectively (p = 0.012). For 378 N1 patients, BCIN+ stratified 21 (6%) and 357 (94%) of patients as low and high risk with 10-y DRFI of 90% (95% CI, 66-97%) and 90% (95% CI, 86-93%), respectively (p = 0.07). Of the 21 patients classified as BCIN+ low-risk, two had BCIN+ scores of 6.75 and 6.73 in close proximity to the cut point (6.93) and experienced DR after 5 years, resulting in the same 10-y DRFI for both BCIN+ low- and high-risk patients. Conclusions: BCI is significantly prognostic for the risk of overall DR (0-10 y) in patients with HR+ HER2+ disease treated with adjuvant trastuzumab-based chemotherapy. Optimization of BCI cut points may further improve prognostic performance in HR+ HER2+. Additional validation in other HR+ HER2+ cohorts treated in the modern setting with anti-HER2-based therapy is warranted, given the small sample size of N0 patients and relatively low DR rate in the late recurrence cohort. In summary, these results provide further evidence of BCI’s utility to support clinical decision-making for adjuvant endocrine therapies for HR+ HER2+ BC. Support: U10CA180821, U10CA180882, U24CA196171, Genentech; Clinicaltrials.gov Id: NCT00005970; https://acknowledgments.alliancefound.org. Citation Format: S. Chumsri, E. Liu, K. Edwards, Y. Wen, Y. Zhang, A. K. Anderson, A. H. Partridge, L. Carey, K. Ballman, E. Perez, K. Treuner, M. Goetz, E. Thompson. Prognostic performance of Breast Cancer Index in patients with early-stage HR+ HER2+ breast cancer (BC) treated with adjuvant trastuzumab: NCCTG N9831 (Alliance) [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 PS3-08-08.

Abstract Background: The PALLAS trial (ABCSG-42, AFT-05, BIG-14-03) investigates adjuvant palbociclib plus endocrine therapy (ET) versus ET alone in patients (pts) with HR+/HER2− early breast cancer. While palbociclib improves outcomes in metastatic settings, final analysis from PALLAS did not demonstrate benefit in survival outcomes from the addition of palbociclib to ET. A number of pts discontinued palbociclib before the planned 2 year duration though degree of palbociclib exposure was not associated with clinical outcomes. This analysis explores factors predictive of palbociclib early discontinuation and dose reductions, including baseline characteristics, toxicities, and patient-reported outcomes (PROs). Methods: Using the safety population of 5736 pts (2840 receiving palbociclib + ET), we assessed early palbociclib discontinuation within a competing-risks framework (competing events: progression, death). Cumulative incidence curves (Aalen-Johansen estimates) and cause-specific hazard models were used to explore associations with clinical and demographic factors (age, menopausal status, stage, race, endocrine therapy type), key toxicities (neutropenia, anemia, nausea), and baseline PROs (patient assessed quality of life [QoL], anxiety, fatigue, pain, frailty/ dependency, depression, and low income. financial difficulties). An automated model selection based on the Akaike information criterion (AIC) starting from the cause-specific hazard model incorporating all considered predictors including PROs. Results: Early discontinuation of palbociclib not due to progression or death occurred in 1171 pts (41.3%); an additional 343 pts (12.1%) stopped due to results of a futility analysis. In 108 (3.8%) and 2 (0.1%) pts treatment was discontinued due to progression or death. Median time to early discontinuation was 7.7 months in pts that discontinued treatment (median interquartile range 3.45-13.60). Very early discontinuation (≤3 months) occurred in 261 pts (9.2%). Dose reductions to 100mg and 75mg occurred in 1566 pts (55.2%) and 951 pts (33.6%) of 2840 pts, respectively. In univariable analyses, higher age, lower N-stage, and specific baseline PROs (baseline QoL, fatigue, anxiety, depression, frailty/ dependency and financial difficulties) were linked with increased risk of discontinuation. The best-fitting multivariable model identified age, nodal stage (N-stage), low quality of life (QoL), and low income as key predictors of early treatment discontinuation. Conclusions: In the PALLAS trial, our findings highlight the importance of integrating PROs into risk prediction of early treatment discontinuation. Additionally, when starting pts on oral targeted therapies in the adjuvant setting, symptom control, social work and financial counseling resources may support pts at higher risk of non-adherence. This is in line with findings from the ESMO Breast QoL analysis (Bjelic-Radisic et al.), which emphasized the added value of subjective patient-reported outcomes alongside objective clinical parameters in understanding treatment burden and adherence. Support: AFT, ABCSG, Pfizer, ECOG-ACRIN, NSABP Foundation, GBG, BIG; https://acknowledgments.alliancefound.org; ClinicalTrials.gov Identifier: NCT02513394. Citation Format: M. Vetter, A. Wiencierz, M. Gnant, D. Hlauschek, C. Kurzeder, C. Grasic Kuhar, N. Zdenkowski, E. Shinn, J. Suga, D. Egle, J. Meisel, S. Antolin-Novoa, E. Munzone, T. Haddad, S. Loibl, A. Holynskyj, C. Fesl, A. Dueck, A. DeMichele, E. Mayer, on behalf of the PALLAS groups and investigators (ABCSG, AFT, BIG,PReCOG, GBG, NSABP). Predictors of early discontinuation of adjuvant palbociclib in early HR+/ HER2- breast cancer: final analysis of the PALLAS trial integrating patient-reported outcomes [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 PS3-07-14.

Abstract Background: (Z)-endoxifen (ENDX) is an oral SERM that dually targets ERα (> 5 ng/ml) and PKCβ1 (>500 ng/ml). It has been tested in the endocrine resistant setting at doses of 20-360 mg/day; however, the optimal dose in an endocrine naïve population is not defined. We explored 10 mg/day dose of neoadjuvant ENDX in the Endocrine Optimization Pilot (EOP) of I-SPY2. Methods: EOP eligibility included pts with Stage II/III HR+ HER2- breast cancer, MammaPrint (MP) low. Pts with MP High1 scores were eligible if clinically node-negative. Pts received ENDX 10 mg orally once daily for 6 cycles (each cycle = 28 days). Premenopausal pts started ovarian function suppression on cycle 2, day 1. ENDX was continued until the day prior to surgery. The primary study endpoint was feasibility, defined as >75% of pts completing >75% of ENDX. Baseline (T0), 3-wk (T1) biopsies, and the surgical specimen (T3) were assessed centrally for Ki-67. Rates of modified preoperative endocrine prognostic index (mPEPI) 0 were reported, defined as pT1-2 pN0, Ki67< 2.7%, or pathologic complete response. A genomic index for sensitivity to endocrine therapy (SET) index was done at T0. Breast MRI measurement of functional tumor volume (FTV) was performed at T0, T1, 12 weeks (T2), and pre-operatively (T3). Blood was collected for tumor informed ctDNA at T0, T1, T2, T3 and for pharmacokinetic (PK) steady state concentrations (Css) at T1. Safety data using CTCAE V5 is reported. Results: Between March 2023 and May 2024, 20 pts were enrolled in this arm. The median age was 52.5 years (range 32 -73), 13 (65%) were premenopausal, and 55% had clinically positive lymph nodes. Tumors were MPHigh1 in 3 pts (15%) and SET2,3 index high in 16 pts (80%). The primary endpoint was met with 95% of study participants completing ≥75% of therapy. The T0 median Ki-67 was 10.5% (range 2-60%). At T1 (n=19) and T3 (n=18), median Ki-67 was 5% (range 0-35%) and 5% (range 0-45%), respectively. The 3-week rate of Ki-67 ≤10% at T1 was 61.5% in premenopausal and 71.4% in postmenopausal women. The rate of Ki-67 ≤10% at surgery was 81.8% in premenopausal and 57.1% in postmenopausal women. An mPEPI score of 0 was observed in 1 (5%) of participants. The median T0 FTV was 8.9 ccs (range 0.9 to 251.1). The median T3 FTV was 1.3 ccs (range 0 to 11.2) and the median change in FTV from T0 to T3 was -72.0% (range -88.5% to -61.6%). ctDNA analysis was performed in 17 pts longitudinally across 64 blood samples.10 pts had positive ctDNA at T0, with 7 converting to ctDNA undetectable during treatment with ENDX. 1/7 pts who was ctDNA negative at T0 became positive at T1 and then reverted to undetectable ctDNA. The other 6 pts remained ctDNA negative at all timepoints. The median ENDX T1 Css was 79.3 ng/mL (range 73.6 - 906.4 ng /mL). The most common side effects reported were Grade 1 hot flush (70%), nausea (40%), fatigue (40%), and insomnia (35%). Grade 2 side effects included fatigue (15%) and night sweats (5%). No dose reductions or discontinuations due to toxicity occurred. Conclusions: ENDX at 10 mg was well tolerated and demonstrated reductions in Ki-67, MRI FTV, and ctDNA. The ISPY2 EOP is currently enrolling patients to ENDX 40 mg/day (intended to dually target ERα and PKCβ1) in combination with abemaciclib (with and without OFS). Citation Format: K. V. Giridhar, M. P. Goetz, C. Yau, A. M. Wallace, C. Falkson, J. Boughey, M. Arora, E. Stringer-Reasor, C. Nangia, C. Gallagher, A. Elias, A. Zimmer, M. S. Trivedi, C. Omene, L. van 't Veer, L. Brown Swigart, G. L. Hirst, W. Symmans, A. D. Borowsky, N. Onishi, N. Hylton, C. Vakalvas, M. Wei, J. M. Reid, S. Alhafaji, N. Chen, R. M. Mukhtar, L. Huppert, O. Opopade, L. J. Esserman, A. Chein. Low dose (Z)-endoxifen in the I-SPY2 Endocrine Optimization Pilot [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 PS3-07-10.

Abstract Introduction: Accurate detection and prioritization of tumor-specific somatic variants is foundational to the development of personalized immunotherapies. Traditional pipelines for neoepitope identification rely heavily on short-read next-generation sequencing (NGS) and DNA-based variant calling, followed by RNA expression filtering and HLA-binding prediction. However, this approach is limited by time-intensive workflows, potential false positives from DNA-only calls, and poor capture of complex isoforms or RNA-level editing. Moreover, the accuracy of neoepitope prediction is constrained by conventional sequence-based HLA binding algorithms that do not account for structural and biophysical features of peptide-MHC interactions, particularly across underrepresented HLA alleles. Methods: To overcome these limitations, we developed a streamlined, sequencing-to-vaccine framework that leverages long-read RNA sequencing for direct detection of expressed somatic variants, including fusions, indels, and single nucleotide variants. Using Oxford Nanopore Technologies’ cDNA-PCR approach, we enable comprehensive, full-length transcript characterization from both fresh and frozen breast tumor samples. Our bioinformatic pipeline, NeoTarget, integrates alignment, variant calling, and neoepitope inference from tumor RNA in a single, modular workflow. A core innovation of this pipeline is HLA-Inception, a deep convolutional neural network trained to predict peptide-MHC class I binding using features derived from molecular dynamics-based modeling of electrostatic potential at the peptide-HLA interface, enhancing generalizability across diverse HLA subtypes. Results: Expanding on previous results, the current NeoTarget pipeline identifies, evaluates, and prioritizes single nucleotide variants, indels, and fusions. To validate this system, we used a set of 9 human breast cancer tumors benchmarked with short read sequencing. Identified neoantigens included most variants shown by clinical short read sequencing and also novel structural variants (i.e., fusions) only revealed with long read sequencing with high confidence. Conclusion: Here, we describe the design and performance of the NeoTarget pipeline, and show proof-of-concept feasibility of applying this fast and cost-effective workflow for HLA-restricted epitope discovery in breast tumors using long-read RNA sequencing. Overall, these methods can be applied to rapidly identify and prioritize neoantigens for personalized neoantigen-based immune therapies. Citation Format: F. Batalini, S. Henry, Y. Zhang, R. Foster, J. M. Gayton, A. Hostal, E. A. Wilson, A. Singharoy, M. Gustafson, B. Pockaj, J. Park, K. S. Anderson. Somatic variant detection using long read RNA sequencing reveals HLA-restricted targets for immunotherapy [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 PS3-06-08.

Abstract Introduction: Patients with ER+/HER2- breast cancer associated with germline pathogenic variants (PVs) in BRCA1, BRCA2 and CHEK2 exhibit distinct clinicopathological features compared to sporadic cases. However, the optimal endocrine therapy strategies for these patients remain undefined. The Breast Cancer Index (BCI) is a validated gene expression-based signature that stratifies patients based on the risk of overall (0-10 years) and late (post-5 years) distant recurrence and predicts the likelihood of benefit from extended endocrine therapy (EET) in early-stage, HR+ breast cancer. Here we utilize BCI to investigate endocrine sensitivity and the predicted EET benefit in a cohort of ER+/HER2- breast cancer patients with BRCA1, BRCA2 and CHEK2 PVs. Methods: BRCA1, BRCA2 and CHEK2 PV carriers with ER+/HER2- breast cancer diagnosed at Mayo Clinic between 1996 and 2024 at Mayo Clinic were identified from a registry tracking germline test result. For comparison, we utilized the BCI Registry, a prospective, multi-institutional tumor registry of patients with early-stage ER+/HER2- breast cancer undergoing BCI testing, regardless of germline PV status. The analysis was restricted to women with invasive, early-stage locoregional breast cancer and available pre-treatment tumor specimens. BCI testing was performed by RT-PCR blinded to clinical outcome. BCI prognostic and BCI predictive categories were compared between the Mayo Clinic germline PV cohort and the BCI Registry using descriptive statistics and Fisher’s exact test. Results: The final analysis included 123 PVcarriers (BRCA1: 36; BRCA2: 40; CHEK2: 47) from the MayoClinic cohort and 2,563 women from the BCI Registry. The proportion of patientsdiagnosed before age 50 was higher among PV carriers—52.8% in BRCA1,50.0% in BRCA2, and 21.3% in CHEK2—compared to 7.0% in the BCIRegistry. PV carriers were also more likely to be premenopausal andnode-positive at diagnosis. Based on BCI score, a significant higher proportionof BRCA1 (75.0%, p=0.002) andBRCA2 (70.0%, p=0.01) PV carriers wereclassified as high risk, compared to 48.5% of patients in the BCI Registry, butno significant difference was seen for CHEK2 PV carriers (46.8%,p=0.88). A significantly higher proportion of BRCA1 PV carriers werepredicted to benefit from EET compared to the BCI Registry cohort (77.8% vs.33.9%, p<0.001), whereas no significant differences in BCI Predictivecategories were observed for BRCA2 or CHEK2 PV carriers. Overall,compared to breast cancer cases in the BCI registry, a significant differencein the distribution of the combined BCI prognostic and predictive categorieswas noted for BRCA1 (p<0.001)and BRCA2 (p=0.02) PV carriers,but not for CHEK2 PV carriers (p=0.66). In particular, BRCA1 andBRCA2 PV carriers were enriched for high-risk tumors with a high likelihoodof EET benefit (66.7% and 37.5%, respectively vs 25.1%, p<0.001 and p=0.02),whereas only a small non-significant increase was observed for CHEK2 PVcarriers (29.8% vs 25.1%, p=0.66) compared to breast cancer cases in the BCIRegistry. Conclusions: Genomicclassification by BCI reveals distinct patterns of endocrine sensitivity andpredicted EET benefit among germline PV carriers, particularly in BRCA1and BRCA2 PV carriers. These findings warrant further investigation andmay inform personalized endocrine therapy strategies for women with germlinePV-associated ER+/HER2- breast cancer. Citation Format: S. Yadav, B. O'Neal, S. Yasir, N. Siuliukina, A. Karki, Y. Zhang, A. K. Anderson, K. Treuner, M. P. Goetz, F. J. Couch. Endocrine Sensitivity and Predicted Benefit of Extended Endocrine Therapy based on Breast Cancer Index (BCI) in BRCA1, BRCA2 and CHEK2 Pathogenic Variant Carriers with ER+/HER2- Breast Cancer [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 PS2-08-25.

Abstract Background: Stromal tumor infiltrating lymphocytes (sTILs) are associated with improved response to chemotherapy and better overall survival (OS) in triple-negative breast cancer (TNBC). Quantification of sTILs via hematoxylin and eosin (H&E) tumor slides offers a widely available method to define a simple, effective surrogate for host anti-tumor immunity. Digitization of H&E slides has rapidly gained acceptance for use in diagnostic pathology and research, opening the door for image-based computational approaches to enumerate sTILs, among other features. Methods: We describe QuTILs - a multilayer perceptron-based framework to detect/enumerate TILs trained on >700,000 cells via The Cancer Genome Atlas Program (TCGA) slide images, implemented in the widely used open-source QuPath digital pathology suite. QuTILs was applied to digital H&E images using standard computing in primary breast tumors from phase 3 breast cancer clinical trials - CALGB 40502 (testing), CALGB 40601 and 40603 (validation) - in total 1,729 total images from 962 unique patients. The aims of this investigation were: 1) to assess the relationship between TIL patterns with overall or event-free survival outcomes; 2) to benchmark diverse image-based characteristics of TIL abundance and spatial architecture; and 3) to evaluate the association between image-based TIL levels and RNA-seq-based immune deconvolution metrics (CIBERSORT, EPIC, quanTIseq). Results: QuTILs average processing time was 7.9 minutes for whole-slide total TIL count and area density on a standard laptop workstation. In CALGB 40502, there was positive but modest correlation between pathologist TILs and QuTILs total TILs %, higher in the TNBC subgroup of CALGB 40502 (Pearson r = 0.55). In Cox proportional hazards models, the CALGB 40502 TNBC cohort showed significant univariate association for total TILs % with increasing decile (higher total TIL%) associated with reduced hazard (hazard ratio [HR]: 0.712, 95% CI: 0.559-0.906; P = 0.006), which remained significant in multivariable model incorporating age, race, and treatment arm (HR: 0.713, 95% CI: 0.556-0.915; P = 0.008). In validation TNBC clinical trial CALGB 40603, marginal TILs % was significant in the univariable Cox model (HR: 0.786, 95% CI: 0.639-0.966). Evaluation of TILs % by QuTILs with RNAseq-based deconvolution metrics in cohort-stratified and deconvolution method-stratified multivariable models showed that decile total TILs % by QuTILs was shown to significantly predict outcome in the EPIC (HR: 0.668, 95% CI: 0.466-0.957) and quanTIseq (HR: 0.646, 95% CI: 0.446-0.936) sets, with a similar magnitude as in clinical Cox, suggesting that RNA-based deconvolution estimates may not supplement the prognostic power of image-based TIL estimates. Exploratory analyses of pre- versus post-neoadjuvant therapy H&E images in CALGB 40603 and CALGB 40601 revealed a significant decrease in QuTILs total TIL% in CALGB 40603 for all pairs (n = 118 pairs, pre-median=9.52%, post-median=6.33%; Wilcoxon signed rank P < 0.001) but no significant change in QuTILs total TIL% among all pairs in CALGB 40601 (n = 82 pairs, pre-median=15.92%, post-median=15.10%; P = 0.886). Conclusions: QuTILs provides a computationally efficient open-source workflow for sTIL identification from digital H&E images that can be deployed on a standard laptop. We present the first evaluation of digital sTIL enumeration in CALGB 40502, CALGB 40603, and CALGB 40601 phase III breast cancer clinical trials and demonstrate significant prognostic association with QuTIL total TIL % among TNBCs across studies. Citation Format: M. Vater, R. Salgado, E. Blige, H. Lefebvre, A. Strahan, M. Gatti-Mays, H. Rugo, K. Ballman, M. Watson, Y. Wen, R. Leon-Ferre, K. Niazi, W. Symmans, L. Carey, K. AbdulJabbar, Z. Li, D. Stover. Qutils: open-source image-based infiltrating immune cell detection and outcomes in calgb 40502, calgb 40603, and calgb 40601 phase iii breast cancer clinical trials [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 PS2-07-27.