ObjectiveTo study the influence of estrogen on zoledronic acid in preventing bone metastasis of breast cancer. MethodsTwo hundred and sixteen breast cancer patients who accepted modified radical mastectomy, chemotherapy, and the prophylaxis of zoledronate acid from January 2006 to December 2009 in this hospital were collected, including luminal A 55 cases, luminal B 63 cases, HER-2 positive 50 cases, triple negative 48 cases. Then these patients were categorized into low estrogen group(n=39) and normal estrogen group(n=177) according to the estrogen level. The patients in the low estrogen group accepted drug induced menopause, in the normal estrogen group didn't accept drug induced menopause. All the patients accepted the therapy of zoledronate acid, then with clinical follow-up for 3-5 years until progressive disease(include neoplasm recurrence, bone metastasis, and other neoplasm metastasis etc.). ResultsThe rate of bone metastasis in the low estrogen group was significantly lower than that in the normal estrogen group (χ2=21.91, P < 0.05). For the patients with luminal A, luminal B, HER-2 positive, and triple negative, the rates of bone metastases in the low estrogen group were significantly lower than those in the normal estrogen group[luminal A:5.13%(2/39) versus 12.43%(22/177), χ2=4.54, P < 0.05;luminal B:7.69%(3/39) versus 13.56%(24/177), χ2=6.04, P < 0.05;HER-2 postive:2.56%(1/39) versus 15.25%(27/177), χ2=3.95, P < 0.05;triple negative:2.56% (1/39) versus 18.08%(32/177), P < 0.05]. The rate of bone metastasis among the different subtype of breast cancer in the low estrogen group was not significant difference(χ2=0.55, P > 0.05). ConclusionsFrom the limited preliminary data, the premenopausal women patients with breast cancer who accepted drug induced menopause afer application of zoledronate acid for preverttion of bone metastasis has a obviously efficacy, and the efficacy has no difference among four molecular subtypes of breast cancer.