O1-15-1 - The Pattern of Tumor Shrinkage is Associated with Prognosis in Luminal Breast Cancer During Neoadjuvant Chemotherapy

Abstract

Background and Objective: Understanding neoadjuvant chemotherapy (NAC) for early breast cancer, the pathological response rate in estrogen receptor (ER)-positive has been low in comparison with those of ER-negative. Therefore, the luminal breast cancer (LBC) must have heterogeneity in response to NAC. We analyzed the patterns of tumor shrinkage after NAC as a surrogate prognostic factor in LBC using MRI.Methods and Results: Of 854 patients who had received NAC in the single institute from Jan. 2000 to Dec. 2009, 265 LBC were retrospectively evaluated for this study. The LBC was defined as ER and/or PgR positive in more than 10% of cancer cells and HER2 negative (IHC 0, 1+ or FISH <2.0). Before and after NAC, the primary lesions were evaluated by MRI in 230 patients. The median observation period was 67.3 months from operation, and recurrence was observed in 43 patients (18.7%). The median age was 49.5 (25-76) years. 227 patients received anthracycline-containing chemotherapy and 200 patients received taxane. There were 24 deaths (10.4%) related to breast cancer. We categorized the patterns of tumor shrinkage by MRI into 6 types; the concentric shrinkage (CS), diffuse decrease (DD), reduction to small foci (RSF), decrease of intensity only (DIO), no change (NC), and enlargement (EL). According to our categorization, the CS was shown in 123 (54.5%), RSF in 9 (3.9%), DD in 76 (33.0%), DIO in 8 (3.5%), NC in 6 (2.6%), and EL in 8 (3.5%), respectively. As expected, there were statistically significant differences in both the median DFS and OS in each patterns of tumor shrinkage (p < 0.001), especially CS pattern had excellent prognosis.Discussion: The tumor shrinkage pattern of MRI could be an important surrogate prognostic factor for NAC in early LBC. Our results suggest that the LBC with non-CS pattern may have the higher heterogeneity which associated with chemotherapy-resistant residual cancer cells.