Comparison of invasive micropapillary and invasive ductal carcinoma of the breast: a matched cohort study.

Background: Invasive micropapillary carcinoma (IMPC) is a rare subtype of breast cancer and is presumed to have a poorer survival outcome than invasive ductal carcinoma (IDC). However, studies for clinical outcomes including imaging features are still scarce. Purpose: To investigate differences in clinical outcomes between IMPC and IDC and to determine prognostic factors indicating survival, including imaging features. Material and Methods: This retrospective study was approved by the institutional review board. Between 2007 and 2012, 308 women diagnosed with IMPC were matched with patients from a group of 6816 women diagnosed with IDC. Patients were matched with 17 clinicopathologic covariates using propensity score matching. Recurrence-free survival (RFS) and overall survival (OS) were compared between the IMPC and IDC groups using Kaplan–Meier estimates. Log-rank tests were performed to compare the survival curves. A Cox proportional hazard model was used to analyze the association of imaging features with survival. Results: In total, 308 matched patient pairs were available for survival analysis. The IMPC group showed worse total RFS (hazard ratio [HR] = 1.63, P = 0.016), local RFS (HR = 2.86, P = 0.042), and distant RFS (HR = 1.85 P = 0.018), but there was no significant difference in OS (HR = 1.30, P = 0.335). A mass with calcification on mammography was an independent factor for worse RFS in the IMPC group and combined IMPC and IDC groups. IMPC subtype was a significant independent factor for worse RFS in the combined groups. Conclusion: The IMPC group showed poorer recurrence-free survival outcomes than the IDC group. A mass with calcification on mammography were associated with poor RFS. [ABSTRACT FROM AUTHOR]