Abstract
PURPOSE: Ductal carcinoma in situ (DCIS) is considered a precursor to invasive ductal carcinoma (IDC), and the coexistence of DCIS with IDC is often observed during the diagnosis of breast cancer. The aim of study is to investigated the clinicopathological features and prognosis of triple-negative IDC with DCIS following neoadjuvant therapy (NAT). Additionally, we explored the risk factors for residual DCIS in these patients post-NAT. METHODS: This study included patients with stages II-III triple-negative breast cancer with histologically confirmed IDC who underwent radical surgery after NAT between January 2011 and December 2021. Baseline data, clinical features, pathological outcomes, and prognostic information were collected and analyzed. RESULTS: A total of 315 patients were enrolled and categorized into the IDC + DCIS (n = 67) and IDC groups (n = 248) according to the composition of the pre-NAT biopsy. The proportion of patients with histological grade G3 (78.2% vs. 61.2%, p = 0.004) and a Ki-67 index > 20% (98.4% vs. 86.6%, p < 0.001) was significantly higher in the IDC group than in the IDC + DCIS group. Although no significant difference was observed in the 5-year overall survival (OS) (93.4% vs. 90.8%, p = 0.298) between the two groups, the 5-year disease-free survival (DFS) (90.6% vs. 83.5%, p = 0.041) of the IDC + DCIS group was significantly better than that in the IDC group. Multivariate analysis demonstrated that IDC + DCIS (HR: 0.502; 95% CI, 0.284-0.952; p = 0.048) was an independent prognostic factor for DFS. In addition, the clinical T3-T4 stage (OR = 3.891; 95% CI, 1.320-15.219, p = 0.040) and clinical N1-N3 (OR = 4.500; 95% CI, 1.495-13.564, p = 0.012) were independent preoperative predictors of residual DCIS after NAT in patients with IDC and DCIS components. CONCLUSION: The presence of DCIS component in patients with triple-negative IDC is associated with lower tumor aggressiveness and improved DFS after NAT compared to patients without DCIS. Additionally, clinical T and N stages are risk factors for residual DCIS after NAT in patients with triple-negative IDC and a DCIS component.