Survival differences among women with de novo stage IV and relapsed breast cancer

Background: The objective of this retrospective study was to determine whether differences in survival exist between women with de novo stage IV and relapsed breast cancer. Patients and methods: Three thousand five hundred and twenty-four women with de novo stage IV or relapsed breast cancer diagnosed from 1992 to 2007 were identified. Disease-free interval (DFI) was defined as the time from the diagnosis of primary nonmetastatic breast cancer to the date of the first distant metastases. Kaplan-Meier product limit method was used to estimate overall survival (OS). Cox proportional hazards model was fitted to determine the association between metastatic disease (relapsed versus de novo) and OS after controlling for other patient/tumor characteristics. Results: Six hundred and forty-three (18.2%) women had de novo stage IV disease and 2881 (81.8%) had relapsed disease. Median follow-up was 19 months. Median OS among patients with de novo stage IV and relapsed disease was 39.2 and 27.2 months, respectively (P < 0.0001). In the multivariable model, women with relapsed disease had an increased risk of death compared with patients with de novo disease (HR = 1.75, 95% confidence interval 1.47-2.08, P < 0.0001). When the multivariable model was stratified by DFI, women with relapsed disease with DFI <6 months, >= 6 months to <2 years, or >= 2 to <5 years each had a significantly higher risk of death compared with women with de novo stage IV disease. The risk of death was not statistically different among patients with relapsed disease with DFI >5 years compared with those with de novo disease. Conclusions: This large cohort study provides further insight into the natural history of relapsed and de novo stage IV breast cancer. DFI plays an important role in the prognosis for patients with relapsed breast cancer.