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

Abstract

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. To investigate differences in clinical outcomes between IMPC and IDC and to determine prognostic factors indicating survival, including imaging features. 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. 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. The IMPC group showed poorer recurrence-free survival outcomes than the IDC group. A mass with calcification on mammography were associated with poor RFS.