Impact of smoking history on the outcomes of women with early-stage breast cancer: a secondary analysis of a randomized study

Abstract

To assess the impact of smoking history on the outcomes of early-stage breast cancer patients treated with sequential anthracyclines–taxanes in a randomized study. This is a secondary analysis of patient-level data of 1242 breast cancer patients referred for adjuvant chemotherapy in the BCIRG005 clinical trial. Overall survival was assessed according to smoking history through Kaplan–Meier analysis. Univariate and multivariate Cox regression analyses of factors affecting overall and relapse-free survival were subsequently conducted. Factors that were evaluated included: age, performance status, number of chemotherapy cycles, T stage, lymph node ratio, estrogen receptor status, adjuvant radiotherapy and smoking history. Kaplan–Meier analysis of overall survival according to smoking status (ever smoker vs. never smoker) was conducted. There was a trend toward a better overall survival among never smokers compared to ever smokers; however, it was not statistically significant (P = 0.098). The following factors were associated with better overall survival in multivariate analysis: older age (P = 0.011), complete chemotherapy course (P = 0.002), lower T stage (P < 0.0001), lower lymph node ratio (P < 0.0001) and positive estrogen receptor status (P = 0.006). Otherwise, the following factors were associated with better relapse-free survival in multivariate analysis: older age (P = 0.001), never smoking status (P = 0.021), lower T stage (P = 0.028), lower lymph node ratio (P < 0.0001) and positive estrogen receptor status (P < 0.0001). Early-stage breast cancer patients with a positive smoking history experienced worse relapse-free survival compared to never smokers. Physicians managing breast cancer patients should prioritize discussion about the benefits of smoking cessation when counseling their patients.

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