For patients with breast cancer, the recommended daily dose is 20-40 mg. Dosages greater than 20 mg per day should be given in divided doses (morning and evening).
In three single agent adjuvant studies in women, one 10 mg tamoxifen citrate tablet was administered two (ECOG and NATO) or three (Toronto) times a day for two years. In the NSABP B-14 adjuvant study in women with node-negative breast cancer, one 10 mg tamoxifen citrate tablet was given twice a day for at least 5 years. Results of the B-14 study suggest that continuation of therapy beyond five years does not provide additional benefit (see CLINICAL PHARMACOLOGY). In the EBCTCG 1995 overview, the reduction in recurrence and mortality was greater in those studies that used tamoxifen for about 5 years than in those that used tamoxifen for a shorter period of therapy. There was no indication that doses greater than 20 mg per day were more effective. Current data from clinical trials support 5 years of adjuvant tamoxifen therapy for patients with breast cancer.
Ductal Carcinoma in Situ (DCIS):
The recommended dose is tamoxifen citrate tablets 20 mg daily for 5 years.
Reduction in Breast Cancer Incidence in High Risk Women:
The recommended dose is tamoxifen citrate tablets 20 mg daily for 5 years. There are no data to support the use of tamoxifen other than for 5 years (See CLINICAL PHARMACOLOGY, Clinical Studies, Reduction in Breast Cancer Incidence in High Risk Women).