Regional Lymph Node Changes on Breast MRI in Patients with Early-Stage Breast Cancer Receiving Neoadjuvant Chemo-Immunotherapy

Establishing breast MRI imaging patterns associated with neoadjuvant immunotherapy is needed to monitor response. We analyzed serial breast MRIs in patients receiving neoadjuvant chemo-immunotherapy on the I-SPY2 clinical trial. Patients with stage 2–3 HER2-negative breast cancer were randomized to weekly paclitaxel (control), weekly paclitaxel and pembrolizumab, or weekly paclitaxel, pembrolizumab and intra-tumoral injection of SD-101, a TLR9 agonist. All patients received AC. Regional lymph nodes were retrospectively evaluated on breast MRI at baseline, 3, 12 and 20 weeks by a single blinded radiologist. MRIs were assessed for development of new regional lymphadenopathy, or increase in the longest diameter or cortical thickness of the largest abnormal regional lymph node. Between 12/2015 and 4/2021, a total of 43 patients enrolled in the control (n = 16) and paclitaxel + pembrolizumab ± SD-101 (n = 27) arms. 12 of 27 patients (44.4