Role of clinical and histologic factors in decision making on adjuvant therapy of small HER2-positive breast cancer.

Abstract

e11053 Background: With increased use of screening mammography for breast cancer (BC), the incidence of small (T1a, b), node negative BC has increased. These cancers are considered low-risk and hence not offered adjuvant (adj) chemotherapy (CT). However, increasing retrospective studies suggest that outcomes in small node negative HER-2 positive BC might be worse than the HER-2 negative tumours of similar size. Current guidelines generally do not recommend adj CT and Trastuzumab (T) for small (T1 a, b) HER-2 positive tumours. As a part of our ongoing audit on the outcome of small HER -2 positive BC, we wished to determine the factors that oncologists consider in decision making on adj treatment of these tumours in the absence of clear guidelines. Methods: Patients (pts) with a diagnosis of node negative T1a, b, HER-2 positive BC treated across our cancer network, between Jan 2008 and Dec 2011, were identified from our electronic database. Results: A total 230 pts had stage T1, HER 2 +ve BC. Out of those 41(17%) pts had tumour size of < 1cm (13, 31%pts were T1a and 28, 74%pts wereT1b) and node negative disease. Median age was 55 years (29-84yrs). 33 Pts had BCS and 8 pts had mastectomy. All pts with BCS received adj radiotherapy and all pts who were ER positive received adj endocrine therapy. 21(51%) out of 41pts received adjuvant CT and T. All pts had anthracycline based CT. The clinical and pathological characteristics of pts who received adj CT and T were as follows; Median age- 50 (33-64years), grade 1- 1(4%), grade 2 – 9(43%), grade 3- 11(53%), LVI present- 2(9%), LVI absent- 7(34%), LVI unknown – 12(57%), ER positive- 16(76%), ER negative – 5(24%). None of the pts had recurred or died at the time of analysis of the data and longer follow up is needed for survival analysis. Conclusions: In the absence of clear guidelines on adj CT and T in node negative small HER-2 positive BC, the oncologists relied on the traditional factors such as grade, ER status in risk stratification and decision on adj therapy. Tumour grade was the most important factor but age and ER status were not discriminating factors in this study. Prospective randomised trials needed to clearly define the role of adj systemic therapy in this group of pts.