Does Existence of Ductal Carcinoma In Situ Accompanying Invasive Ductal Carcinoma Lead to Different Clinicopathological Features and Clinical Outcome? Report of a Breast Cancer Registry

Ductal carcinoma in situ (DCIS) is widely recognized as the precursor of invasive ductal carcinoma (IDC). We aimed to compare clinicopathological characteristics and prognosis between IDC with and without coexisting DCIS stratified by biological subtypes to evaluate the clinical outcome of these two groups.
Data from 5814 patients with IDC (32.4) and IDC/DCIS (67.6%), who underwent surgery from December 1993 through December 2019, were retrospectively assessed. We evaluated the prognosis of IDC with coexisting DCIS in different molecular subtypes.
IDC/DCIS patients were younger (P < 0.001). They also presented with a low tumor grade and had less lymph node involvement compared with the pure IDC patients. Compared with the patients with IDC, luminal B subtype was more frequent in those with IDC/DCIS, with 19.4% versus 13.2 %; human epidermal growth factor receptor-2 enriched subtype was also more frequently observed, with 12.2 vs. 8.7%. The 5-year disease-free survival (DFS) was higher in the IDC/DCIS patients (P = 0.036). The survival outcomes significantly improved in the cases with a higher amount of DCIS. The presence of coexisting DCIS (P =0.038), tumor size (P < 0.001), lymph node status (P = 0.005), lymph vascular invasion (P = 0.02), and molecular subtypes (P < 0.001) were found to be DFS-associated independent prognostic factors.
DCIS along with IDC were associated with improved prognosis. The presence of DCIS may be a marker of lower aggressiveness, and could be noticed as a prognostic factor in future treatment algorithms.