Clinical Outcomes and Prognostic Factors in Epithelial-Myoepithelial Carcinoma (EMC) of the Breast.

Abstract

Background: Most published data on EMC consists of individual case reports, and survival outcomes are not clearly defined to guide evidence-based management.

Methods: All women with a histologic diagnosis of EMC irrespective of age and stage at diagnosis till 2018 in the National Cancer Database were included (N = 111). Overall survival (OS) was compared among groups using the Kaplan-Meier and log-rank methods.

Results: The median age at diagnosis was 67 years, and 101 (88.6%) were over 50 years of age. Ten percent were ER+/Her2-, 29.7% were ER-/Her2-, 0.9% were Her2+, 5.4% were ER+/Her2 unknown, 24% were ER-/Her2 unknown, and 29.7% had no data on ER status. Most patients underwent surgical resection (91.9%), whereas chemotherapy and radiation were utilized in 35.2% and 40.6% of the patients, respectively. At a median follow-up of 67.6 months, the 5-year OS was 74.3%. Among patients who received chemotherapy or radiation, the 5-year OS was 80.1% (vs. 68.9% in nonrecipients, P = .02) and 83.1% (vs. 68.5% in nonrecipients, P = .03), respectively. The 5-year OS was 82.7%, 76.5%, and 50% for tumor ≤ 2 cm, 2 to 5 cm, and > 5 cm respectively (P = .009). Chemotherapy or radiation treatment were associated with improved OS in tumors >5 cm (both P < .05).

Conclusion: EMC demonstrates distinctive clinicopathologic features and receptor status. Receipt of adjuvant chemotherapy and radiation demonstrates improved survival in larger tumor (> 5cm) although small sample size and lack of recurrence data limit this conclusion. Studies using larger cohorts are needed to demonstrate objective efficacy of systemic treatment in lymph node positive and metastatic EMC.