Distinct clinic and ultrasound imaging manifestations associated with HER2-low expression in triple-negative breast cancer.

BACKGROUND: To determine whether HER2-low tumors exhibit a particular subtype among individuals with triple-negative breast cancer (TNBC). METHODS: This multicenter study enrolled 539 patients diagnosed with TNBC who underwent surgery after neoadjuvant chemotherapy. Comparative analyses of clinicopathological factors, qualitative ultrasound imaging characteristics (BI-RADS), quantitative ultrasound imaging characteristics (Radiomics), and clinical outcomes, including pathologic complete response (pCR), event-free survival (EFS), and overall survival (OS), were conducted between patients with HER2-low and HER2-0. RESULTS: Patients with low Ki67 expression were more common in HER2-low patients as compared to HER2-0 patients. Based on ultrasound BI-RADS characteristics, the difference in vascularity pattern was observed between the two different HER2 status, where HER2-0 tumors presented more avascularity (12.0%vs. 6.3%). Ultrasound radiomics characteristics revealed the differences in shape, minimum voxel intensity, and texture. In the overall cohort, no significant association was found between HER2-low expression and pCR, EFS, or OS (p > 0.05). Compared to HER2-0, HER2-low patients exhibited a lower pCR rate among individuals with low T stage. Conversely, in patients with high T stage, the pCR rate was higher, although this finding did not achieve statistical significance (p = 0.065). Among non-pCR patients, HER2-low status was also associated with improved EFS. CONCLUSION: Compared with HER2-0, HER2-low tumors are distinct in clinicopathological factors, ultrasound imaging characteristics, response to neoadjuvant chemotherapy, and prognosis. Our results provided a better understanding of HER2-low status in TNBC by detailed subgroup analysis, which can offer valuable insights for managing HER2-low patients in clinical practice.