Variation in type of adjuvant chemotherapy received among patients with stage I breast cancer: A multi-institutional Portuguese cohort study

•In a retrospective multi-institutional Portuguese cohort study 40% of patients with early breast cancer had Stage I disease.•Almost one-quarter of patients with pathological stage I breast cancer were treated with adjuvant chemotherapy.•When treated with chemotherapy, most patients receive non-intensive regimens such as AC (doxorubicin plus cyclophosphamide).•Taxane-based non-intensive regimens, such as TC (docetaxel plus cyclophosphamide), were infrequently used.•Striking institutional variations in utilization of chemotherapy were noted, ranging from 0 to 43.4%.