Abstract P6-10-06: Metachronous Contralateral Breast Cancer (CBC) Has More Aggressive Biology and Clinical Characteristics Compared to Synchronous Bilateral Breast Cancer (BBC)

Abstract

Abstract Purpose: Bilateral breast cancer is an uncommon clinical entity. There is no specific treatment strategy and controversial issues concerning diagnostic criteria, management and classification exist. Method: In order to address some of these issues, a prospective analysis (data recorded upon patients first presentation) of an electronic breast cancer database at a tertiary cancer centre was performed. Patients’ epidemiologic characteristics, clinical profile, genomic analysis information and the tumours’ histopathology were analyzed. Results: Out of 900 patients treated for breast cancer between 2006 and 2009, 44 diagnosed with bilateral disease (5% of total)having a median age of 53 years(range 32-73). 16 of them (36%)suffered from synchronous disease and 28 (64%)from metachronous { >3 months apart between the initial diagnosis and subsequent contralateral breast tumour). Genetic analysis revealed 3 patients with inherited breast cancer syndromes (2 with BRCA1 and one with CDH-1 mutation). Among those with synchronous BBC 63% (10/16)were postmenopausal, 50% (8/16)had a positive family history for breast cancer and upon initial diagnosis 80% (13/16)of them presented with early stage disease (stages I,II).Contralateral disease was diagnosed incidentally. In contrast to these patients with synchronous BBC,57% of the patients (16/28)with metachronous CBC were premenopausal and 68% (19/28)had advanced disease (stages III,IV) upon the second diagnosis. Etrogens’ use didn't differ among the two groups, obesity was more common in patients with metachronous CBC, and smoking in the synchronous BBC patients. Of the 88 tumours, 81(92%) were invasive, with ductal adenoCa being the more common (53% of specimens). Of synchronous BBC tumours 12/16 (75%)were HR+ positive and 80%(13/16) expressed the same biologic features bilaterally. Of the metachronous tumours, upon initial diagnosis,26% were triple negative and only 7% were found with HER2 amplification, compared with 41% and 26% respectively in the second diagnosis. Conclusions: Synchronous BBC is less prevalent than Metachronous CBC, has more favourable characteristics (earlier stage at diagnosis, hormonal receptor positivity), and occurs mainly among postmenopausal women with positive family history. Metachronous CBC is more common in premenopausal women and has a tendency to change its biological and clinical characteristics to a more aggressive phenotype (triple negative, HER2 amplification) between initial and latter diagnosis. If this phenomenon is a result of previously given chemo/radio-therapy or it reperesents the natural evolution to a second primary, remains a challenging question to be answered. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P6-10-06.