Prognosis of women with stage IV breast cancer by HER2 status and trastuzumab treatment: An institutional based review

Abstract

1018 Background: HER2 +ve status is traditionally known to be associated with poor prognosis. Recent studies have shown that the addition of trastuzumab to the treatment of women with HER2 +ve disease significantly improves survival in early and advanced stage breast cancer. The purpose of this retrospective study was to determine if the addition trastuzumab in a cohort of women with stage IV HER2 +ve breast cancer improves prognosis beyond that of women with HER2 -ve disease. Methods: Women with de novo stage IV or recurrent breast cancer diagnosed between 1991–2007, with known HER2 status, who had not received trastuzumab in the adjuvant setting, were identified from the M. D. Anderson database. Disease was classified into three groups: a) HER2 -ve disease, b) HER2 +ve disease without first-line trastuzumab treatment, c) HER2 +ve disease with first-line trastuzumab treatment. Overall survival (OS) was defined as the time from the date of first distant metastasis to the date of death or last follow-up and was estimated using the Kaplan-Meir product method and compared between groups with the log-rank test. Cox proportional hazards were used to determine associations between OS and HER2 status after controlling for patient (pt) characteristics including year and age of diagnosis and site of first metastases. Results: The final analyses included 2,091 pts. One hundred and eighteen (5.6%) pts had HER2 +ve disease without trastuzumab treatment, 191 (9.1%) had HER2 +ve disease and trastuzumab treatment and 1,782 (85.3%) pts had HER-2 -ve disease. Median follow-up was 16.9 months. One year survival in pts with HER2 -ve disease, HER +ve disease who received trastuzumab and those with HER2 +ve disease who did not receive trastuzumab was 75.1% (95% CI 72.9%, 77.2%), 86.6% (95% CI 80.8%, 90.8%) and 70.2% (95% CI 60.3%, 78.1%) respectively. In a multivariable model women with HER2 +ve disease who received trastuzumab had a 44% reduction in the risk of death compared to women with HER2 -ve disease (HR 0.56, 95% CI 0.45–0.69, p<0.0001). Conclusions: The introduction of trastuzumab has altered the natural history of HER2 +ve breast cancer. Our results show that the addition of trastuzumab improves the prognosis of women with HER2 +ve disease above and beyond that of women with HER2 -ve disease. No significant financial relationships to disclose.