Abstract P6-09-07: Triple negative apocrine carcinomas as a distinct subtype of triple negative breast cancer: A case-control study

Abstract

Abstract Introduction. Invasive apocrine carcinoma of the breast is a rare type of breast cancer (BC), pure apocrine carcinoma constitutes <1% of all BC. Mammary apocrine epithelium has a characteristic steroid receptor profile that is negative for full length estrogen receptor-alpha and progesterone receptor and is androgen receptor positive. Conflicting data are available on the outcome of this type of disease: few studies reported significantly different prognosis of triple negative (TN) apocrine carcinomas when compared to most non-apocrine triple negative (NA-TN) tumors. The aim of this study is to report our long-term experience in a single-center series of TN apocrine tumors. Methods. We analyzed clinical and pathological features of a series of TN apocrine carcinomas treated at our Centre in a 15-year period. Clinical and pathological characteristics and outcomes have been compared with a control series of NA-TN tumors treated during the same follow up period. Local relapse-free survival (LRFS), distant metastases-free survival (DMFS), and overall survival (OS) have been evaluated and compared between groups of patients. Results. Forty-five TN apocrine carcinomas were analyzed. The mean age at diagnosis was 60 years (range 34-83 years). The proportions of apocrine tumor grades varied, with G1 being seen in 6.8% of patients, G2 in 51.1%, and G3 in 40.1%. The majority of apocrine carcinomas had small tumor size (T1: 72.7%; T2: 27.3%), and negative axillary nodal status (66.7%). The series was compared to a homogenous control group of 45 NA-TN patients. The mean age was 54 years (range 32-79 years), affected by high grade (G3: 53.7%), small tumor size (T1: 87.5%; T2: 12.5%), and mostly negative axillary nodal status (82.9%). LRFS in the apocrine group was 85% and 78% at 5- and 10-year, respectively. LRFS in the NA-TN group was 90% and 79% at 5- and 10-year, respectively. No difference was evidenced between groups (HR 1.44 95%CI 0.62-3.79; p=0.39). DMFS in the apocrine group was 85% and 85% at 5- and 10-years, respectively. DMFS in the NA-TN group was 85% and 75% at 5- and 10-year, respectively. DMFS was significantly better in the apocrine group (HR 0.69 95%CI 0.28-1.62). OS in the apocrine group was 86% and 83% at 5- and 10-year, respectively. OS in the NA-TN group was 86% and 63% at 5- and 10-years, respectively. OS was significantly better in the apocrine group (HR 0.57 95%CI 0.26-1.18). Conclusions. Apocrine carcinomas represent a clinic-pathological distinct group of triple-negative BC, characterized by significantly more favorable clinical prognosis in terms of long-term disease-related morbidity or mortality when compared to NA-TN tumors. Citation Format: Meattini I, Pezzulla D, Carta GA, Becherini C, Perna M, Grassi R, Garlatti P, Desideri I, Scotti V, Bernini M, Sanchez LJ, Orzalesi L, Nori J, Bianchi S, Livi L. Triple negative apocrine carcinomas as a distinct subtype of triple negative breast cancer: A case-control study [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P6-09-07.