Trastuzumab-based treatment has dramatically improved the outcomes of HER2-positive (HER2+) metastatic breast cancer (MBC) patients, with some patients achieving prolonged survival times. In this study, we aim to identify factors that are associated with long-term survival. Patients with HER2+ MBC treated with anti-HER2 target therapy were identified. Patients were grouped according to overall survival (OS) and categorized as long-term survivors (LTS, OS ≥ 5 years), or non-long-term survivors (non-LTS, OS < 5 years). Descriptive statistics and multivariable logistic regression modeling were used. A sensitivity analysis was carried out, including only patients diagnosed before 2007; therefore, 5 years of potential follow-up was possible. 1063 patients with HER2+ MBC diagnosed between 1994 and 2012 and treated with anti-HER2 therapy were identified. Among them, 154 (14.5 %) patients were categorized as LTS (median OS 92.2 months). Among LTS, 63.4 % were HR-positive and 32 % had de novo stage IV disease. Hormone receptor positivity (OR) 1.69; 95 % CI 1.17-2.44), resection of metastases (OR 2.38; 95 % CI 1.53-3.69), and primary breast surgery in patients with de novo stage IV (OR 2.88; 95 % CI 1.47-5.66) were associated with improved long-term survival. Greater number of metastatic sites (≥3 vs. 1, OR 0.41; 95 % CI 0.23-0.72) and visceral metastases (OR 0.61; 95 % CI 0.4-0.91) were associated with poor survival. Hormone receptor positivity, low burden of disease, metastasis to soft and bone tissues, and surgical management with resection of the metastatic site and the primary tumor were associated with long-term survival in patients with MBC who received anti-HER2 treatment.
Keywords: Clinical predictors; Long-term survival; Metastatic HER2-positive breast cancer.