A population-based study on the patterns of use of different chemotherapy regimens in Swiss patients with early breast cancer.

Background: There is considerable heterogeneity in the use of chemotherapy in early breast cancer (BC), despite international recommendations issued from the NCCN, NIH and the St.Gallen bi-annual conference.
Methods: We included 1,535 patients from seven Swiss cancer registries between 2003 and 2005 receiving chemotherapy for stage I to III BC. Chemotherapy was categorised into (a) FAC/FEC, anthracyclines followed by CMF or anthracycline-taxane combinations (FAC-T) (781 patients) and (b) other chemotherapy regimens such as CMF/AC (EC) (754 patients). Predictors for choosing FAC-T over non-FAC-T chemotherapy were separately determined in all patients and in ER-negative patients (n = 496) by multivariate logistic regression analysis.
Results: The use of FAC-T increased significantly over time, from 44% in 2003 to 55% in 2005. BC stage III (versus stage I-II) and nodal positivity were the predominant predictors for using FAC-T chemotherapy in the adjusted model (odds ratio (OR) 4.1, 95%-confidence intervals (CI) 2.6-6.3 and OR 3.0, 95%-CI 2.0-4.4, respectively). In high-risk ER-negative BC patients, poor histological differentiation was more important to choose FAC-T chemotherapy (OR 3.8, 95%-CI 1.9-7.5) than tumour stage or nodal status. The use of FAC-T chemotherapy varied substantially among the seven geographic regions, from 20% in rural Grisons-Glarus to 73% in Zurich.
Conclusions: Tumour biology is a predominant factor for choosing FAC-T over older chemotherapy regimens in patients with ER-negative early BC, but improvements should be made to reduce the substantial regional heterogeneity. Further epidemiological studies should assess how the use of FAC-T chemotherapy is affecting clinical outcome in patients with early BC and different risk profiles.