Biologic behavior and long-term outcomes of breast ductal carcinoma in situ with microinvasion

BACKGROUND Ductal carcinoma in situ with microinvasion (DCIS-Mi) generally has favorable prognosis, but the long-term outcomes of DCIS-Mi and the biologic evolution from ductal carcinoma in situ (DCIS), DCIS-Mi, to DCIS with T1a breast cancer (DCIS-T1a) has not been specified. The aim of our study was to explore the biological and prognostic features of DCIS-Mi, compared with pure DCIS and DCIS-T1a. RESULTS After a median follow-up of 31 months, the 3-year estimated disease free survival(DFS) rate of DCIS-Mi patients was significantly lower than that of pure DCIS patients (89.5% vs 97.1%, P=0.009). Patients with DCIS-Mi or DCIS-T1a tumors had comparable 3-year estimated DFS rates (89.5% vs 94.3%, P=0.13). No significant difference in overall survival (OS) was found among different groups (99.6%, 100% and 99.1% for DCIS, DCIS-Mi and DCIS-T1a, P=0.797). In chemotherapy and trastuzumab-naive DCIS-Mi patients, human epidermal growth factor receptor2 (HER2) positivity (HR=21.8, 95%CI, 1.7-286.8, P=0.019) were independent predictor of worse DFS on multivariate analysis. METHODS During September 2002 and December 2014, 602 breast cancer patients who underwent radical surgery were retrospectively reviewed. Three hundred and fifty-nine patients (59.6%) had pure DCIS, 84(14.0%) and 159(26.4%) were diagnosed as DCIS-Mi and DCIS-T1a. Clinico-pathological features were compared between different subgroups. CONCLUSIONS DCIS-Mi displayed a comparable survival to that of DCIS-T1a and a more aggressive biological nature than pure DCIS. Patients with HER2-positive DCIS-Mi had a worse survival and adjuvant chemotherapy plus target therapy needs to be further optimized in those patients.