Prognostic Significance and Predictive Value of Circulating Tumor Cells in Invasive Lobular Breast Carcinoma—An Exploratory Analysis of the STIC CTC Trial

ILC sheds more CTC than NST, likely owing to underlying biological differences. Although the ≥5 CTC/7.5-mL threshold remained a valid prognostic marker for both, it was predictive of chemotherapy benefit in NST but not in ILC. These findings highlight differences in biomarker utility between ILC and NST, affecting both threshold relevance and treatment response.