Impact of persistence on survival of patients with breast cancer treated with endocrine therapy in Northeast China: a prospective study

The purpose of this prospective study is to investigate the impact of endocrine treatment persistence on the survival of patients with estrogen receptor-positive breast cancer treated with endocrine therapy and identify the risk factors influencing the treatment persistence. We enrolled 1085 patients from Northeast China who were diagnosed as stage I-III, estrogen receptor-positive breast cancer between January 2007 and December 2010. The prognostic factors for disease-free survival (DFS) and overall survival (OS) of patients were identified using univariate and multivariate Cox proportional hazards regression models. Multiple logistic regression analysis was done to determine the possible risk factors for non-endocrine treatment and treatment discontinuation. Among the patients enrolled, 598 (55.1%) underwent 5 years of endocrine therapy, 278 (25.6%) less than 5 years, and 209 (19.3%) non-endocrine therapy. OS rates in the continuation, discontinuation, and non-endocrine treatment groups were 97.8%, 92.6% and 74.3%, and DFS 97.5%, 86.2% and 69.9%, respectively. After adjusting for pathological and socioeconomic factors, non-endocrine therapy and discontinuation were independent predictors for DFS and OS. Elderly patients (≥ 65 years), those living in suburban and rural areas, locally advanced patients, and receiving no radiotherapy and/or chemotherapy were more likely to receive non-endocrine therapy and discontinue endocrine treatment. In conclusion, the prospective study demonstrate that the persistence of endocrine treatment is low in estrogen receptor-positive breast cancer patients in Northeast China. Non-endocrine treatment and early discontinuation serve as independent prognostic factors for both DFS and OS of breast cancer patients treated with endocrine therapy.