Wright, J. L.

Abstract Objectives: In the RadComp randomized trial, we compared radiation dose to cardiac substructures in patients treated with proton versus photon radiation therapy (RT) ; evaluated changes in cardiac-specific health-related quality of life (HRQOL) outcomes from baseline to 6 months following RT; and determined associations between radiation dose volume histogram (DVH) parameters and changes in cardiac-specific HRQOL. Methods: The study cohort included patients with locally advanced breast cancer enrolled on RadComp who completed treatment per protocol, had available radiation DVH metrics for all cardiac substructures, and completed both the baseline and at least one follow-up cardiac-specific HRQOL over the 6 months post-RT. Cardiac-specific HRQOL measures included PROMIS fatigue, PRO-CTCAE shortness of breath (SOB) (severity and interference with daily activities), and PRO-CTCAE chest pain, chest tightness, and angina (frequency, severity, and interference). Detailed dose volume histograms (DVH) for cardiac substructures included the whole heart, left ventricle (LV), right ventricle (RV), left atrium (LA), right atrium (RA), and left anterior descending artery (LAD) were derived. The Wilcoxon rank-sum test was used to compare dose distributions between photon and proton RT. Associations between DVH metrics and HRQOL outcomes were evaluated using repeated-measures linear regression via generalized estimating equations with an independent working correlation structure. All models were adjusted for RT type, age, cardiovascular risk factors, surgery type, laterality, ethnicity, education, timepoint, and race. Additional stratified analyses was performed according to laterality (right versus left + bilateral). Results: Across 1160 RadComp participants, RT exposure to cardiac substructures differed significantly between proton and photon RT and by laterality. Median mean heart dose was lower with protons, 0.9 Gy (Q1, Q3 0.49, 1.46), compared to photons 2.83 Gy (Q1, Q3 1.49, 4.52) (p< 0.001), and lower for right-sided disease, 0.91 Gy (Q1, Q3 0.44, 1.55), compared to left and bilateral 1.99 Gy (Q1, Q3 1.11, 3.63) (p<0.001). Similarly, for the LAD, LA, LV, and RA, mean proton dose was significantly lower (p<0.001). However, for the whole heart, RA, and RV, maximum doses to small-volume parameters and dose to 0.03cc were higher with proton RT. PRO-CTCAE measures of HRQOL were generally favorable at all timepoints across all participants, and grade ≥3 toxicity was rare (≤5.5%) for all measures. The PROMIS Fatigue T-Score increased from baseline (median 49 [Q1, Q3 46, 57]) to end of RT (55 [Q1, Q3 49, 63]), and returned to baseline levels at 6 months (p<0.001). While there were no significant differences in PRO-CTCAE SOB severity (p=0.24) and interference (p=0.11) over time, PRO-CTCAE chest pain worsened compared to pre-RT with respect to frequency (p<0.001), severity (p<0.001), and interference (p=0.008). However, the absolute changes were small. No DVH metrics were significantly associated with any cardiac-specific HRQOL outcomes. Stratification by laterality yielded similar results. Conclusions: Proton RT generally conferred significantly lower doses to the heart and cardiac substructures compared to photon RT. HRQOL outcomes were favorable across all participants, with fatigue returning to baseline, no change in SOB parameters, and a slight worsening of chest pain outcomes over 6 months following RT. Cardiac-specific HRQOLs appear not to be significantly affected by RT dose to cardiac substructures within the first 6 months post-RT. Other organs at risk that could also impact cardiac HRQOL endpoints, longer follow-up, and major cardiac events will be evaluated in future analyses. Citation Format: J. L. Wright, K. Ko, W. Kenworthy, W. Bosch, L. Braunstein, G. Freedman, E. Gillespie, R. Jimenez, S. Pugh, H. Lu, M. Pankuch, N. Remmes, W. Straube, W. Zou, E. Berlin, L. Fang, S. MacDonald, N. Taunk, J. Kim, A. Thukral, A. Taghian, M. Mishra, R. Mutter, V. Croog, D. Boggs, J. Urbanic, N. Ohri, A. Chawla, T. Meier, L. Rosen, M. Fegundes, O. Cahlon, K. Hoffman, A. Ferriozzi, J. Bekelman, A. Lin, B. Ky. Associations Between Cardiac Radiation Dose Volume Metrics and Cardiac Specific Health Related Quality of Life for Patients with Breast Cancer Randomized to Proton versus Photon Radiation on the RadComp 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 RF6-04.

Abstract Introduction: Hormone receptor positive (HR+), HER2- breast cancer (BC) is the most common subtype of BC. Despite advances in chemotherapy and endocrine therapy optimization, local and systemic recurrences frequently occur, especially for patients with node-positive disease. Recent data suggest a subset of patients with this tumor phenotype may benefit from the addition of anti-Programmed Death-1(aPD1) to neoadjuvant chemotherapy. However, T-cell infiltration (TCI), a biomarker of response to aPD1 and chemotherapy, is typically low in this BC subtype. Preclinical models show that combining preoperative radiation therapy (preop RT) with immune checkpoint inhibitors can enhance TCI and anti-tumor immunity. We conducted the first randomized trial to test whether no-, low- or high-dose RT combined with aPD1 increases TCI and improves responses in non-irradiated, metastatic lymph nodes in HR+/HER2- BC (NCT04443348). Materials & Methods: Eligible patients had ER and/or PR≥10%, HER2 negative invasive BC with clipped and biopsy-proven positive axillary node(s), cT1c-T4c, cN1-3, and at least one of the following criteria: grade 3 or grade 1-2 with cN2-N3, Ki67 >20%, or high genomic assay score. Between 2022-2024, 51 patients from 10 centers were randomized to no (0Gy; control arm), low (9Gy) or high (24Gy) doses of preop RT to the primary tumor with concurrent pembrolizumab followed by a 2-week tumor biopsy. Stratification factors were T1c vs. T2-4 and N1 vs. N2-3. Patients subsequently received pembrolizumab with 12 weeks of paclitaxel, followed by 4 cycles of adriamycin-cyclophosphamide (q2wk or q3wk) with pembrolizumab (200 mg q3 wks or 400 mg q6 wks). Surgery and adjuvant therapy followed standard-of-care. Dual co-primary endpoints were 2wk tumor TCI and nodal pathologic complete response (ypN0) at time of definitive surgery. TCI was assessed by multiplex immunofluorescence (pan-cytokeratin, CD3, CD8), using a rank-based Immunoscore (range 0-1), compared to baseline reference biopsies via two-tailed Mann-Whitney test. ypN0 was evaluated non-comparatively. Secondary endpoints included pCR and Residual Cancer Burden (RCB) 0/1. Results: Among 51 patients enrolled, 49 were evaluable for TCI and 48 for the ypN0 endpoint. Median age was 49.5 years (range 23-78). The cohort had a high-risk clinical profile: 92% had cT2-4, 50% N2-3, and 62% grade 3 tumors. Median ER and PR positivity were 90% (20-100) and 68% (1-98), respectively. Multifocal or multicentric tumors were present in 32%. TCI was assessed at 2 weeks post-treatment. The proportion of tumors with TCI in the upper quartile increased with RT dose escalation: 31% (0Gy), 40% (9Gy), and 53% (24Gy). Median TCI scores at 2 weeks were 0.60 (0Gy), 0.56 (9Gy), and 0.82 (24Gy), compared to a median baseline value of 0.50 from untreated reference samples. A statistically significant increase in TCI was observed only in the 24Gy cohort relative to the untreated group (p=0.027). 70.8% underwent mastectomy, with 39.6% receiving immediate reconstruction. 8% experienced G2/3 wound complications, balanced across arms. Median number of lymph nodes removed was 6.5 (1-42). The overall ypN0 rate was 29%, and 24%(0Gy), 29%(9Gy) and 33%(24Gy) per arm. pCR/RCB 0-1 rates were 18%/27% in the entire cohort and 6%/18%(0Gy), 29%/29%(9Gy), and 19%/33%(24Gy), respectively. Conclusion: The addition of 24Gy preop RT to aPD1 significantly increased tumor TCI in HR+/HER2- early-stage BC. Non-irradiated nodal response rates were promising despite over one-third of the study population with grade 1/2 tumors and high disease burden, laying the foundation for a future randomized trial comparing the efficacy of this novel approach against standard of care for node-positive HR+/HER2- BC. Citation Format: G. Gupta, A. Y. Ho, F. Gharibpoor, Y. Abdou, J. D. Anampa, R. C. Blitzblau, B. C. Calhoun, D. L. Casey, S. F. Dent, L. A. Carey, J. R. Bellon, L. E. Warren, J. Lu, T. J. Hieken, A. G. Taghian, A. Bardia, T. Traina, G. Plitas, K. Gallagher, K. Daugherty, A. Thompson, I. Krop, A. Wolff, E. Mittendorf, J. Fox, H. Garber, E. Hwang, A. J. Khan, J. P. Loene, R. Mutter, S. Patil, C. Santa-Maria, B. V. Vincent, J. L. Wright, L. Spring.Primary Results from the HR+/HER2- Cohort of TBCRC-053 (P-RAD): A Randomized Trial of No, Low, or High Dose Preoperative RADiation with Pembrolizumab and Chemotherapy in Node-Positive, HER2-Negative 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 GS2-05.

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 (<10% vs 10-60% vs >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%) <10%, 698 (52%) 10-60%, and 7 (0.5%) >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<0.001; Table). sTILs analyzed as a categorical variable (<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 <30% vs ≥30% sTILs, an association with pCR was also seen in univariable analysis for both HER2+/ER+ disease (p<0.001) and HER2+/ER- disease (p=0.045), though in multivariable analysis with clinical factors, sTILs >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.