NICE recommends new drug to prevent breast cancer in families at high risk.
Women whose close family members have had breast cancer, particularly at an early age may benefit from medicines to reduce their risk of developing the disease.
New evidence demonstrated if 1,000 women at high risk of breast cancer took anastrozole for 5 years 35 cases of breast cancer would be prevented, compared to 21 if they took tamoxifen.
NICE recommends anastrozole is offered for 5 years to women at high risk of breast cancer unless they have severe osteoporosis. And clinicians should consider offering it to women at moderate risk of breast cancer.
The recommendations appear in the draft update of the Familial breast cancer guideline out for consultation.
Professor Mark Baker, director of the centre for guidelines at NICE, said: "Our draft guideline update recommends the use of anastrozole as a first line treatment for postmenopausal women at high or medium risk of breast cancer who don't have osteoporosis.
"The evidence examined by the committee suggests anastrozole will not only reduce the number of breast cancer cases in these women compared to tamoxifen, but it is also a more cost effective option."
The current list price of an anastrozole is £1.19 for 28 tablets.
The draft guideline also recommends genetic testing for BRCA1 and BRAC2 mutations in women under 50 with triple negative breast cancer.
Testing should only be offered if the woman does not have a family history of breast or ovarian cancer.
The draft guideline update is out for consultation until 29 December 2016.