Since the rate of persistence to adjuvant endocrine therapy such as 5-year aromatase inhibitors (AI) would decrease over time in patients with hormone-sensitive breast cancer, it is necessary to investigate if a patient support program could modify patients' beliefs and improve their persistence to AI treatment. This was a prospective, multicenter, controlled, observational study to evaluate the efficacy of a patient support program in improving postmenopausal patients' persistence to adjuvant AI medication for early stage breast cancer (NCT00769080). The primary objective was to compare the rates of 1-year persistence to upfront adjuvant AI for patients in the two observational arms (standard treatment group and standard treatment plus patient support program group). In this study, 262 patients were enrolled in the standard treatment group and 241 patients in the standard treatment plus patient support program group. The mean 1-year persistence rates were 95.9 and 95.8% for the standard treatment group and the standard treatment plus patient support program group, respectively (P=0.95). The mean times to treatment discontinuation were 231.2 days in the standard treatment group and 227.8 days in the standard treatment plus patient support program group, with no statistically significant difference between the two groups (P=0.96). There was also no statistically significant difference in the reason for treatment discontinuation (P=0.32). There was a significant relationship between the patient centered care questionnaire and poor persistence (odds ratio=3.9; 95% CI, 1.1-13.7; P=0.035), suggesting that the persistence rate of patients with whom the doctor always or usually spends time is greater than that of patients with whom the doctor sometimes or never spends time. Patients' persistence to adjuvant AI medication for postmenopausal, early stage breast cancer is relatively high in the first year and is not significantly increased by adding a patient support program to standard treatment.