choose to take up the NHS offer of mammography screening. Breast Cancer UK do not offer advice on mammography screening for breast cancer. As mentioned, BCUK believes women should decide whether they participate in the NHS screening programme and that their decision should be based on a full understanding of the potential risks and benefits. We encourage women to read about screening protocols (available online and in freely available booklets) and discuss individual options with their physicians. For information about mammography screening please see the following websites: Public Health England (2013). NHS breast screening helping you decide. The Independent UK Panel on Breast Cancer (2012). The Benefits and Harms of Breast Cancer Screening: An Independent Review. Q. Does HRT cause breast cancer? A: Hormone replacement therapy, or HRT, can increase breast cancer risk. Combined HRT (a combination of oestrogen and progestin (synthetic progestogen) increases risk considerably more than oestrogen alone. The longer HRT is taken, the higher the risk; it is estimated that HRT increases the risk of breast cancer 2.7 fold, if it is taken for around five and a half years. Risk is immediately reduced when HRT is stopped and after 5 years or less risk is no longer evident. Most studies have found HRT containing oestrogen only slightly elevates breast cancer risk. However, this type of therapy may not be suitable for all women. Q. Does the contraceptive pill and other types of hormonal contraceptive increase breast cancer risk? A: The contraceptive pill contains synthetic oestrogen and/or synthetic progestogen. Studies have use of combined oral contraceptives (oestrogen and progestogen) slightly increases breast cancer risk. The risk is no longer evident 10 years after use has stopped. Some studies suggest progestogen-only contraceptives may not be associated with increased risk. More studies are needed to confirm this. Other types of hormonal contraceptives include injections and hormone releasing intrauterine systems which contain progestogen, and patches and vaginal rings which use both oestrogen and progestogen. There are fewer studies into risk associated with these types of contraceptives, although the risks are thought to be similar to the contraceptive pill. Some studies have indicated that use of injections increases breast cancer risk, although more studies are needed to confirm this.
Q. Does fluoride in drinking water increase breast cancer risk? A: No studies have demonstrated a link between fluoride in drinking water and an increased risk of breast cancer. Fluoride is added to drinking water to prevent tooth decay. There is limited evidence fluoride may increase the risk of bone cancer, however most studies, including a recent British study, conclude there is no evidence of an association between bone cancer and fluoride in drinking water. Water fluoridation may cause early stage dental fluorosis (dental mottling) in children. Q. Does chlorine in water increase breast cancer risk? A: Currently, there is insufficient evidence to conclude that chlorine in drinking water increases breast cancer risk, although there are some studies that claim chlorinated water slightly increases risk. Chlorine is added to water as a disinfectant. It can react with organic matter in water and generate chlorination by-products such as chloroform. The International Agency for Research on Cancer (IARC) classifies some chlorination by-products as possible causes of cancer. Q. Does drinking cow’s milk increase breast cancer risk? A: It is unclear whether a diet high in milk and dairy increases breast cancer risk. Concerns stem from the fact that cow’s milk usually comes from pregnant cows and contains bovine hormones, including bovine oestrogen. Drinking cow’s milk increases levels of human insulin growth factor 1 (IGF-1), and women with higher levels of this growth factor have a slightly increased breast cancer risk. However, although some studies suggest a diet high in milk and dairy products increases breast cancer risk, others suggest there is no increase, or even in some cases a reduced breast cancer risk. Q. Does smoking increase breast cancer risk? A: Most recent studies and meta-analyses conclude there is a modest increase in breast cancer risk for those who smoke or are passive smokers (e.g.). The difficulty in demonstrating a link may be partly because of interactions with other factors which influence risk. For example, a recent study showed that exposure to light at night is a breast cancer risk factor,