Abstract P2-13-04: Impact of the adjuvant treatment with trastuzumab in HER2 positive breast cancer in the real-world setting. Analysis of two cohorts (1997-2005/2006-2015) in 1970 patients
Authors: Rodriguez CA , Garcia-Gomez J , Ribelles N , Gavila J , Pernas S , Rodriguez-Lescure A , Urrutikoetxea A , Pernaut C , Lopez A , Garcia-Mata J 
Published: May 2019

INTRODUCTION: Although large randomized trials assessing the benefit of adjuvant trastuzumab in HER2-positive (HER2+) breast cancer have clearly demonstrated a significant improvement in long-term survival, it is necessary to know the impact of the use of trastuzumab adjuvant in the real life population, which includes patients frequently excluded from clinical trials, such as those with very small tumors without node involvement, or advanced age. The objective of this study is to describe the outcomes of women who received adjuvant trastuzumab for HER2+ cáncer since it was approved in 2006, compared with a previous cohort of HER2+ patients not treated with trastuzumab in 7 Spanish centers.

METHODS: Women with newly diagnosed stage I-III, HER2+ breast cancer, between 1997 and 2015 were included in the study. Two cohorts were considered: The No-Trastuzumab cohort (No-T), between 1997 and 2005, and the Trastuzumab cohort (T) with trastuzumab-treated women between 2006 and 2015. Kaplan-Meier estimates were used to evaluate DFS and OS. Additionally, cohorts were analyzed by pathologic tumour size, lymph node involvement and hormonal receptor status to stratify outcome measures.

RESULTS: A total of 2134 patients were identified. In 164 cases, data were insufficient or the follow-up incomplete. Therefore, the final analysis included 1970 patients, of whom 539 belong to the "No-T" cohort and 1431 to the "T" cohort. The median follow-up was 81 months. Median age: 53 years [22-98]. A total of 699 patients had T1 tumors [43% in the "No-T" cohort vs 33% in the "T" cohort]. 55% of the cases were N0 [58% and 54% in the "No-T" and "T" cohorts respectively]. The status of the hormonal receptors was well balanced between groups [36% ER negative in both]. Regarding the type of adjuvant treatment administered, in the "T" cohort more patients received adjuvant chemotherapy [65% vs 97%] and also in the “T” group combinations of taxanes and anthracyclines were more frequent [14% vs 72%]. The proportion of adjuvant endocrine therapy was similar in both groups [37% vs 34%].

In the “T” cohort, median Disease Free Survival (DFS) was not-reached, compared with 149 months in the “No-T” group. 5-year DFS was 83% vs 65% respectively [p&lt;0.001]. 5-year DFS was also superior and statistically significant in all the subgroups analyzed, including patients with T1 tumors (87% vs 57%), N0 (87% vs 78%), patients T1N0 (88% vs 74%) and HR positive (86% vs 71%) or negative (78% vs 50%). Similarly, Overall Survival (OS) was increased in patients treated with Trastuzumab (median: 224 months vs not-reached, 5-year OS: 92% vs 75% [p &lt;0.001].) 5-year OS was also statistically superior in the T1 subgroup (92% vs 72%), and N0 (95% vs 88%). [p&lt;0.001 in all subanalysis].

CONCLUSIONS: Adjuvant treatment with Trastuzumab under conditions of real clinical practice in HER2+ early breast cancer, shows a highly significant benefit in terms of DFS and OS, regardless of the stage of the disease or other clinical variables. A very important benefit was reached in patients with small tumors, node-negative disease, or both conditions (T1N0). The benefit was also obtained regardless of the expression of hormonal receptors.

Citation Format: Rodriguez CA, Garcia-Gomez J, Ribelles N, Gavila J, Pernas S, Rodriguez-Lescure A, Urrutikoetxea A, Pernaut C, Lopez A, Garcia-Mata J. Impact of the adjuvant treatment with trastuzumab in HER2 positive breast cancer in the real-world setting. Analysis of two cohorts (1997-2005/2006-2015) in 1970 patients [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-13-04.