Abstract PS1-06-22: Impact of breast tumor size discrepancy between contrast-enhanced and conventional ultrasonography on axillary lymph node metastasis

Abstract Background: Surgical procedures for breast cancer are determined by tumor size and axillary lymph node (ALN) metastasis. A size increase on contrast-enhanced ultrasonography (CEUS) compared with conventional ultrasonography (cUS) is often observed, for which the reasons are unclear. As vascular remodeling at the invasive front plays a critical role in metastasis, we hypothesized that this discrepancy reflects the metastatic potential. Purpose: This study investigated the association between size discrepancies on cUS and CEUS in relation to ALN metastasis in breast cancer. Methods: This retrospective study enrolled 259 patients who underwent surgery for breast cancer with sentinel lymph node biopsy or dissection of the ALN after preoperative cUS and CEUS examinations. The eligibility criteria included tumor size by cUS ranging from 20 to 50 mm and the absence of preoperative adjuvant therapy. Patients were grouped into a DISCR (i.e., tumor size discrepancy ≥ 4.0 mm between CEUS and cUS measurements) and other (non-DISCR) group. The primary outcome was ALN metastasis, defined by pathological evaluation, and mono-and multivariate analyses were performed. Secondary outcomes were the 5-year recurrence-free survival rates. Results: There were 94 patients in the DISCR and 165 in the non-DISCR groups. No size differences were observed between the DISCR and non-DISCR groups (p = 0.82), whereas the DISCR group had a significantly higher rate of ALN metastasis than the non-DISCR group (p < 0.01). Multivariate analyses showed a discrepancy of ≥ 4.0 mm was a-risk for ALN metastasis (relative risk: 5.836, 95% confidence interval [CI]: 2.52-13.5). The 5-year recurrence-free survival rate was lower in the DISCR (0.750, 95% CI: 0.632-0.868) than in the non-DISCR (0.924, 95% CI; 0.870 - 0.978) group. Conclusion: An increase in contrast-enhanced ultrasonography tumor size is helpful for assessing axillary lymph node metastasis and prognosis. Citation Format: T. Oshino, H. Shimizu, M. Sato, M. Nishida, T. Horie, S. Tsuneta, F. Kato, M. Hosoda, I. Yokota, K. Kudo, M. Takahashi. Impact of breast tumor size discrepancy between contrast-enhanced and conventional ultrasonography on axillary lymph node metastasis [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 PS1-06-22.