Magnetic resonance imaging tumor regression shrinkage patterns during neoadjuvant chemotherapy versus neoadjuvant immunochemotherapy in triple-negative breast cancer (NeoMDSS-TN-SP): A nonrandomized, prospective cohort study.

Abstract

e12601 Background: Previous studies have shown that the tumor regression shrinkage pattern (SP) of triple-negative breast cancer (TNBC) during neoadjuvant chemotherapy (NAC) is more likely to present with concentric shrinkage (CS), which is associated with a pathological complete response (pCR). Since immunotherapy and chemotherapy have different antitumor mechanisms, it is reasonable to believe that there may be different SPs between neoadjuvant immunochemotherapy (NAIC) and NAC. This NeoMDSS-TN-SP prospective study aimed to investigate whether tumor SPs differed between NAIC and NAC in TNBC, as well as to calculate the correlation between SP and efficacy. Methods: In this prospective, single-center, nonrandomized cohort study, eligible patients with stage II-III TNBC received NAIC or NAC and underwent MRI at baseline, after the first cycle of neoadjuvant therapy, and preoperatively. Based on the MRI after the first cycle, the tumor SPs were grouped into three categories: CS, diffuse decrease, and no change or enlargement. The primary end point was the difference in SP between the two treatment groups. Secondary endpoints included the correlation between SP and treatment efficacy. This study is registered with ClinicalTrials.gov, number NCT04909554. Results: Ninety-nine patients were enrolled from January 2019 to July 2021; 65 received NAC and 34 received NAIC. Baseline characteristics were similar between the two groups. More patients in the NAIC group achieved pCR after surgery than in the NAC group (82.4% vs. 44.6%, p=0.0003). In the NAC group, more patients showed CS (53.8%), and patients with the CS pattern had a significantly higher pCR rate than those with diffuse decrease or no change/enlargement (65.7% vs. 21.7% vs. 14.3%, p=0.0007). In the NAIC group, although a higher proportion of patients showed diffuse decrease (67.6%), all three SP categories had relatively high pCR rates, so pCR was not correlated with SP (85.7% vs. 82.6% vs. 75.0%, p=0.9029). Conclusions: This is the first study to investigate the tumor regression SP of NAIC in TNBC patients. Compared to traditional chemotherapy, NAIC was more prone to diffuse regression, but the relatively high pCR rates had no correlation with the SPs during neoadjuvant therapy. Clinical trial information: NCT04909554 . [Table: see text]