The impact of new chemotherapeutic and hormone agents on survival in a population-based cohort of women with metastatic breast cancer

Abstract

Background: Over the past decade, a number of new therapeutic agents have become available in the treatment of metastatic breast cancer (MBC). This study characterized the use and assessed the impact on survival of population-based access to new agents for the treatment of MBC.

Methods: The dates of release in British Columbia of 7 new systemic agents for MBC during the 1990s were used to construct 4 time cohorts. All patients with a first diagnosis of distant metastases in each of the time cohorts were identified and characterized, and their survival was compared. Cox proportional regression modeling was used to assess for predictors of survival.

Results: In total, 2150 patients with a first distant metastases diagnosed during 1 of the 4 cohort intervals were identified. Baseline characteristics between cohorts were similar, except a greater proportion of the later cohorts received adjuvant chemotherapy (P < .001), had positive estrogen receptor status (P = .01), and had a longer median time from initial diagnosis to MBC (P < .001). Survival in Cohort 1 (1991-1992) and Cohort 2 (1994-1995; median, 438 days and 450 days, respectively) was similar. Survival was longer in Cohort 3 (1997-1998; median, 564 days; P = .002) and improved further in Cohort 4 (1999-2001; median, 667 days; P = .05). In multivariate analysis, the later cohorts were associated independently with improved survival (P = .01 and P < .001, respectively).

Conclusions: Population-based access to new therapeutic agents for MBC appeared to be associated with improved survival. To the authors' knowledge, this is the first study to date that demonstrates, from a population-based perspective, improving survival over the past decade for women with MBC.