Ductal carcinoma in situ with micro-invasion (DCIS-M) is defined as invasive focus no more than 1 mm in greatest dimension in a background of ductal carcinoma in situ (DCIS). Generally DCIS-M exhibits favorable prognosis, but the long-term outcomes of DCIS-M, the impact of molecular subtype on survival, and the biologic evolution of DCIS(from DCIS to DCIS-M, then 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-M, compared with pure DCIS and DCIS-T1a.
Five hundred and ninety eight female breast cancer patients who underwent breast surgery between September 2002 and December 2014 in Shanghai Ruijin Hospital were retrospectively reviewed. 360 patients had DCIS, 84 and 161 were diagnosed as DCIS-M and DCIS-T1a. Clinicopathological features were collected and compared between different types of breast cancer. Kaplan-Meier curves were applied to estimate disease-free survival (DFS) and overall survival (OS). Cox regression was used to identify independent prognostic factors.
Among all patients, the median age at diagnosis was 52 (range, 25–86) years. After a median follow-up of 30 (range, 2-144) months, the 3-year estimated DFS rate of DCIS-M (89%) was significant lower than pure DCIS (96.8%, P = 0.008) but was similar to DCIS-T1a (94.2%, P = 0.088). HER2 positivity (HR 26.30, P= 0.013) and young age (HR 24.66, P= 0.016) were independent predictors of worse DFS on multivariate analysis.
DCIS-M had a worse DFS outcome compared with pure-DCIS and a similar prognosis to DCIS-T1a. No significant difference in OS were found among the three groups. In DCIS-M, HER2 overexpression appears to be an independent predictive factor of outcome.
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All authors have declared no conflicts of interest.