2729 - Predictors of Survival in Triple-Negative Breast Cancer Patients Treated with Neoadjuvant Chemotherapy, Surgery, and Radiotherapy

S. Shao¹, W. Shi², L. Zhang¹, J. Meng², X. M. Guo³, and X. Yu²; ¹Fudan University Shanghai Cancer Center, Shanghai, China, ²Department of Radiation Oncology, Fudan University Shanghai Cancer Center; Department of Oncology, Shanghai Medical College, Fudan University; Shanghai Clinical Research Center for Radiation Oncology; Shanghai Key Laboratory of Radiation Oncology, Shanghai, China, ³Department of Radiation Oncology, Fudan University Shanghai Cancer Center; Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China

Purpose/Objective(s): The heterogeneity and highly aggressive behavior results in more complex molecular characteristic of TNBC and poorer prognosis. TNBC had been classified into different mRNA expression-based subtypes based on multiomic analysis. Furthermore, immunohistochemically (IHC)-related biomarkers were provided to simplify the classification. Neoadjuvant chemotherapy (NAC) is the standard treatment for locally advanced breast cancer and is widely used in high-risk patients (HER2+ or triple-negative). As the global prevalence of personalized cancer care, treatment strategies based on tumor nature characteristics are of great significance. Materials/

Methods: TNBCs treated with NAC were classified into two subtypes: basal-like immune-suppressed (BLIS) and non-BLIS subtypes. Disease-free survival (DFS) was compared between BLIS and non-BLIS subtypes using the Kaplan-Meier method. The influence of lymph node ratios (LNR) on survival outcomes was also analyzed. LNR was calculated by dividing the number of positive nodes by the total number of surgically removed nodes. The calculated values were divided into LNR categories (LNRC): low = 0.20, intermediate 0.21–0.65, and high>0.65.
Results: The 4-year DFS rates were 74.8% and 56.1% in non-BLIS and BLIS subtypes, respectively (P = 0.035). Factors independently predicting DFS were molecular subtyping (HR = 2.071, P = 0.034) and ypN (HR for ypN1-2 = 4.891, P = 0.018, ypN3 = 7.444, P = 0.008). For the BLIS group, significant differences were observed when comparing ypN2 (P < 0.05) and ypN3 (P < 0.05) with ypN1, respectively. Superior DFS was observed in the cohort with ypN0 over ypN3 in the non-BLIS group (P < 0.05). The difference between LNR-low and LNR-high in the BLIS group was statistically significant (P < 0.05). In the non-BLIS group, subgroups with low, intermediate or high LNRC showed significant differences (P < 0.05).
Conclusion: Molecular subtyping is a potential prognostic factor, and the non-BLIS subtype yields favorable outcomes. Residual nodal disease after NAC can also discriminate between favorable and unfavorable outcomes. Individualized strategies for radiotherapy after NAC of different molecular subtypes are worth looking forward to.