Can HRT or the oral contraceptive pill increase a woman’s risk of breast cancer?

Many women use the oral contraceptive pill or hormone replacement therapy (HRT) to manage fertility, troublesome symptoms of heavy periods or the menopause. As with all forms of treatment, it is important to be aware of the possible side-effects and risks of any medication you take, particularly for those taken over a long period of time. In this informative article, revered consultant breast oncologist Dr Shiroma De Silva-Minor expertly explains how these commonly prescribed treatments can affect a person’s breast cancer risk and also sheds light on the various lifestyle changes which are most impactful in reducing the likelihood of developing the disease.

Can HRT or the oral contraceptive pill increase a woman’s risk of breast cancer?

The oral contraceptive pill and breast cancer

To answer this question, it's important to understand the impact of hormonal changes on breast tissue. Different hormonal exposure over the course of a woman's lifetime has an impact on her breast cancer risk. Pregnancy and breastfeeding reduces the total number of lifetime menstrual cycles and therefore exposure to specific hormones associated with breast cancer, meaning that multiple pregnancies and breastfeeding, especially if done for longer, are protective.

Going through puberty early, a late menopause or never being pregnant increases a woman’s lifetime number of menstrual cycles and again increases risk of breast cancer.

The oral contraceptive pill (OCP) can increase risk but on average, it is estimated that less than one per cent of breast cancer cases in the UK are related to the OCP. The risk is also proportional to the duration of a woman’s use of the OCP, increasing from seven per cent for five years’ use to fourteen per cent for ten years’ use.

Also, this risk reduces once a woman stops taking the OCP and returns to that of a non-user ten years after stopping. Breast cancer risk also varies according to the type of oral contraceptive pill a woman takes; combined Oestrogen-Progesterone or Oestrogen only.

HRT and breast cancer

The breast cancer risk for a woman undergoing hormone replacement therapy (HRT) is between one in fifty and one in two hundred and depends on many factors, such as the type of HRT taken (Oestrogen only or combined), the duration of treatment and obesity. HRT is thought to account for two per cent of cases of breast cancer.

If you are taking the oral contraceptive pill or HRT and are concerned about the risk of breast cancer, you should speak to your doctor. As with every intervention in medicine, it's important to weigh up pros and cons in each individual case. While there are risks, it’s also important to consider the advantages of these forms of treatment. HRT can have a positive and protective effect on the bones and heart and the OCP can be taken for contraceptive reasons but can also to help control painful or heavy periods.

Which lifestyle factors contribute to breast cancer risk?

Lifestyle

Although many risk factors for breast cancer are out of our control, the good news is that a number of lifestyle changes can be very impactful, particularly those relating to diet, alcohol consumption and exercise. In fact, Breast Cancer UK estimates that around thirty per cent of breast cancer cases in the UK can be prevented by making lifestyle changes.

Alcohol

Alcohol is a very important factor but I find that a lot of my patients are not aware that alcohol can increase breast cancer risk. In the Million Women study, an observational cohort study conducted by Oxford University following almost 700,000 post-menopausal, healthy women, various dietary links with increased risk of cancer were looked into. The strongest link was found to be with alcohol intake. Alcohol causes DNA damage and also increases oestrogen and other hormone levels associated with breast cancer. In breast cancer survivors, even as little as three drinks a week can increase the risk of recurrence. Therefore, it's important that women are making informed choices.

Diet

Diet is very closely linked to breast cancer risk. To help reduce this risk, a plant based diet, ideally with plant based protein in every meal, is recommended. Plenty of fruit, vegetables and roughage has also been shown to reduce cancer risk in the Million Women study amongst many others. As well as the avoidance of processed foods to reduce breast cancer risk, the following foods are recommended:

• cruciferous vegetables, such as cauliflower, kale, turnip and radish
• fermented food, such as miso, kimchi and kefir
• antioxidant foods, including rich coloured fruit and vegetables like citrus and berries
• nuts and spices such as cinnamon, turmeric and cardamom

I am often asked about sugar feeding cancers. It's important to know that this risk doesn’t so much relate to the sugar itself but rather the body's response to sugar and other high calorie or processed foods. Intake of these foods causes the body to produce insulin and insulin-like growth factors which can stimulate cancer cell growth.

Not only what we eat, but also when we eat is important in reducing breast cancer risk. Eating late at night, skipping breakfast, snacking and grazing throughout the day can increase the risk of breast cancer. There is a growing body of evidence for the health benefits of intermittent fasting (or time restricted diets) which involves eating two meals within a six to eight hour window before fasting for sixteen to eighteen hours. This has been shown not only to help with weight control, but also reduces blood pressure, controls blood sugar levels, improves heart and brain function and our ability to cope with stress as well as boosting the immune system.

Obesity

Being obese or overweight post menopause can increase breast cancer risk as fat cells produce oestrogen. A BMI of less than twenty-five reduces cancer risk as well as the likelihood of stroke, heart attack and dementia.

Exercise and activity

Many studies conducted over the past years have consistently shown that an increase in physical activity is linked to a lower breast cancer risk.

If you are concerned about your risk of breast cancer and wish to schedule a consultation with Dr De Silva-Minor, you can do so by visiting her Top Doctors profile.