Abstract P5-20-02: Predictors of long-term survival in a large cohort of patients with HER2-positive (HER2+) metastatic breast cancer (MBC).
Authors: Chavez Mac Gregor M , Lei X , Giordano SH , Valero V , Esteva F , Mittendorf EA , Gonzalez-Angulo AM , Hortobagyi GN 
Published: August 2014

Background: Numerous studies have examined prognostic factors for survival in breast cancer patients (pts), but few have focused on long-term survival among pts with HER2+ MBC receiving HER2-targeted therapy. In this study we sought to evaluate the clinical characteristics and predictive factors of long-term survival in this group of pts.

Methods: All pts with HER2+ MBC treated with HER2-directed therapy at MD Anderson Cancer Center were identified by retrospective review of the Institutional Breast Medical Oncology database. HER2 status was determined by IHC or FISH. Patient characteristics were analyzed using descriptive statistics. Overall survival (OS) was measured from the date of diagnosis of the first distant metastasis to the date of death or last contact. Pts were grouped according to OS and categorized as long term-survivors (LTS, OS ≥5 years), or non-long term survivors (non-LTS, OS &lt;5 years). A multivariable logistic regression model was fit to examine the relationship between long-term survival and patient characteristics.

Results: We identified 1603 pts diagnosed with HER2+ MBC between 1994 and 2012 and treated with HER2-targeted therapy. A total of 154 (14.5%) pts were categorized as LTS (median follow-up 80 months, median OS 92.2 months); in this subgroup we identified 10 pts that survived ≥10 years. There were 909 (85.5%) not-LTS (median follow-up 20 months, median OS 27.6 months). Among LTS, 67.5% of the pts were younger than 50 years old; 63.4% had HR-positive tumors and initial stage at the time of diagnosis was I in 11.9%, II in 39.9%, III in 16.3% and stage IV de novo in 32% of the pts. 5-year survival estimates demonstrated differences according to age (31% in patients ≤50 years vs. 25% in patients &gt;50, p = 0.005); stage at diagnosis (25% for stage I-III vs. 36% for stage IV de novo, p &lt; 0.001); HR status (35% in HR-positive vs. 22% in HR-negative, p &lt; 0.001) and number of sites of metastatic disease (33%, 25% and 19% for 1, 2 and ≥3 sites, p &lt; 0.001). By multivariable analysis, we identified that HR-positivity (OR = 1.69; 95% CI 1.17–2.44), number of sites of metastases (3 vs. 1 OR = 0.41; 95% CI 0.23–0.72), location of metastases (visceral vs. bone-soft tissue OR = 0.61; 95% CI 0.4–0.91), resection of metastases (OR = 2.38; 95% CI 1.53–3.69) and primary breast surgery among pts with stage IV de novo (OR = 2.88; 95% CI 1.47–5.66) were significantly associated with long-term survival.

Conclusions: Some patients with HER2+positive MBC have an excellent outcome, particularly younger pts with HR-positive tumors, low burden of disease and non-visceral metastases in which multidisciplinary treatment is favored. In the era of HER2-targeted therapies, 14.5% of the patients are long-term survivors. To our knowledge this is the largest series identifying the characteristics of this group of patients.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P5-20-02.