Impacts of smoking on endocrine treatment response in a prospective breast cancer cohort

Abstract

Background: The association between smoking and breast cancer prognosis remains unclear. The purpose of this study was to investigate whether preoperative smoking was associated with prognosis in different treatment groups.

Methods: This population-based cohort consisted of 1065 breast cancer patients without preoperative treatment included between 2002 and 2012 in Lund, Sweden. Smoking status was examined in relation to patient and tumour characteristics, and prognosis in different treatment groups.

Results: At the preoperative visit, 21.0% smoked. Median follow-up time was 5.1 years. Overall, in the 1016 patients included in the survival analyses, there was no significant association between smoking and risk of breast cancer events (adjusted hazard ratio (adjHR): 1.45; 95% confidence interval (CI): 0.95-2.20). For the 309 aromatase inhibitor (AI)-treated patients ⩾50 years with oestrogen receptor-positive (ER+) tumours, smoking was associated with risk of breast cancer events (adjHR: 2.97; 95% CI: 1.44-6.13), distant metastasis (adjHR: 4.19; 95% CI: 1.81-9.72), and death (adjHR: 3.52; 95% CI: 1.59-7.81). Smoking was not associated with breast cancer events or distant metastasis in other treatment groups.

Conclusions: Preoperative smoking was only associated with an increased risk for breast cancer events and distant metastasis in AI-treated patients. If confirmed, smoking status should be taken into consideration when selecting an endocrine therapy.

Figure 1

Flowchart of patients in different analyses in relation to their preoperative smoking status. AIs=aromatase inhibitors; ER=oestrogen receptor; TAM=tamoxifen.

Figure 2

Flowchart of smoking status among alive and event-free patients using ‘last observation carried forward'. Out of the 206 preoperative smokers, 21 patients (10.2%) reported no further smoking during the first postoperative year. Out of the 810 preoperative non-smokers, seven patients (<1%) reported smoking during the first postoperative year.

Figure 3

Kaplan–Meier estimates showing the association between preoperative smoking status and risk for breast cancer events. As this is an ongoing cohort, there are fewer patients with longer follow-up times. (A) There was no association among all patients. (B) There was no association among patients ever treated with chemotherapy. (C) Smoking was associated with a tendency towards an increased risk for breast cancer events among patients ever treated with radiotherapy. adjHR=adjusted hazard ratios; CI=confidence interval.

Figure 4

Kaplan–Meier estimates showing the association between preoperative smoking status and risk of breast cancer events, distant metastases, and death due to any cause among patients ⩾50 years with ER+ tumors. As this is an ongoing cohort, there are fewer patients with longer follow-up times. (A) Smoking was associated with a three-fold increased risk for breast cancer events among AI-treated patients. (B) Smoking was associated with a four-fold increased risk for distant metastases among AI-treated patients. (C) Smoking was associated with a three-fold increased risk of death due to any cause among AI-treated patients. (D) There was no association between smoking and risk for breast cancer events among TAM-treated patients. AdjHR=adjusted hazard ratios; aIs=aromatase inhibitors; CI=confidence interval; ER=oestrogen receptor; TAM=tamoxifen.