Abstract PS2-01-13: Pixels to Prognosis: Predicting Response to NAST Using Multiparametric Imaging Combining Tomosynthesis, Shear Wave Elastography and Doppler

Abstract Background: Predicting response to NAST may help tailor treatment, maximize pCR rates and de-escalate surgery (BCS, SLNB). We tested if multiparametric imaging- using mammography breast tomosynthesis (DBT), ultrasound shear wave elastography (SWE) & color Doppler after 2 NAST cycles (post2NAST) of their changes from baseline correlate with NAST response and predict pCR. Methods: In this prospective study, 100 non-metastatic breast ca pts (39 TNBC, 31 HER2 enriched, 28 Luminal B like) receiving NAST underwent imaging at baseline, post2NAST, after completing NAST. Changes in tumor dimensions, volume, density, stiffness, vascularity were correlated with pCR & RCB after surgery. Results: 40% achieved pCR. Post2NAST DBT density changes predicted pCR (p<0.0001); 92% patients with pCR had decreased density. Density post2NAST was strongly associated with response- 87% low-density tumors had low RCB (0-1), c.w. 88% persistent high-density tumors had poor response (RCB 2-3)- 87% sensitivity, 80% specificity. Post2NAST, ≥17.6% reduction in max diam predicted pCR with 82.5% sensitivity, 70% specificity (AUC = 0.817), while ≥39.4% vol. reduction predicted pCR with 87.5% sensitivity, 70% specificity (AUC = 0.824). Mean & max SWE values from tumor core, peritumoral zone & large ROI were studied. Only mean, max peritumoral SWE baseline→ post2NAST reduction was significantly assoc. with pCR (p=0.038, 0.020 respectively). Absolute SWE values post2NAST or post NAST across all regions didn’t distinguish responders. Baseline→ post2NAST reduction in Adler vascular score (semi-quantitative Doppler grading that classify vascularity/angiogenesis) was significantly assoc. with pCR, p=0.002. Patients achieving ‘No flow’ had highest pCR (71.4%). A ≥2-point drop demonstrated high 87% specificity for pCR. Mean 13-point vascular imaging score declined significantly (baseline 9.6→ 6.9 post2NAST). On ROC analysis, score ≤6 post2NAST predicted pCR with 77% sensitivity, 60% specificity (AUC = 0.695, p=0.001). Subtype analysis: HER2+ tumors had greatest DBT density reduction after NAST (87.1%, p=0.038), closely mirroring their highest pCR rates. TNBC &HER2+ subtypes had greater stiffness reductions on SWE post2NAST, esp. in peritumoral mean/max & large ROI values (AUC 0.70). While Adler score regression (to “no flow”) was commonest in TNBC, subtype difference didn't reach significance. Luminal B tumors consistently showed least favorable imaging response. Conclusions: Early imaging response post2NAST, especially DBT density/volume reduction & peritumoral SWE stiffness reduction strongly predict pCR, outperforming absolute values. Multiparametric imaging combining DBT, SWE & Doppler vascular scores (Adler & 13-point) offers a non-invasive, early surrogate for treatment response, enabling timely therapy tailoring, and predicting pCR. Citation Format: G. Agarwal, S. Dariya, S. Mayilvaganan, G. Chand, A. Mishra, N. Mohindra, V. Agrawal, P. Mishra. Pixels to Prognosis: Predicting Response to NAST Using Multiparametric Imaging Combining Tomosynthesis, Shear Wave Elastography and Doppler [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 PS2-01-13.