Endocrine therapy

This information is meant as a supplement to the information you have received from your doctor and/or nurse practitioner. In the first part we will elaborate on the process of the endocrine therapy. In the second part you will find information about possible side-effects and advice towards managing those, and in the third part you’ll find information on the departments and people you can get in touch with if necessary.

Endocrine therapy

Hormones are small particles our body makes. They are released into the bloodstream to convey messages to different organs in the body: starting, enhancing, diminishing and stopping processes. Breast cells need estrogen and progesterone to function and to grow. These are predominantly made in the ovaries, after which they travel to the breast cells and connect with the receptors that are on the cells.

If a breast cancer cell also contains these so-called ‘endocrine receptors’, hormones could cause the tumor cells to grow. About 80% of patients with breast cancer have endocrine positive breast cancer, meaning their tumor will contain these receptors. Only patients that are endocrine positive can be treated with endocrine therapy.

The better describing name for endocrine therapy would be anti-hormonal therapy because the result of the treatment will be lowering the production and/or effect of hormones in the body. This way the growth of a tumor and/or metastasis is inhibited, and new tumors are prevented.

Endocrine therapy can be used before and/or after surgery. It is also used in palliative care, to prevent worsening of the cancer.

The choice in terms of type of endocrine therapy is based on your menopausal state, and the phase of your treatment. The most used endocrine therapies are tamoxifen, letrozol, anastrazol, fulvestrant, gosereline and leuproreline.

Using endocrine therapy will cause (chemical) menopause in the woman body. This doesn’t necessarily mean that you can’t get pregnant. It is advised to use contraceptives while using endocrine therapy, due to increased risk of developing disorders of the unborn child. If you wish to pursue pregnancy whilst still on endocrine therapy, consult with your physician.

Side effects

The side effects that are most common with endocrine therapy will be discussed, including advice on how to manage them. The first thing to make clear is that the hereafter named side effects can but don’t have to occur. Some people have a lot of side effects, others slim to none. Most side effects are temporary. The mentioned advices are not individually made, but provide guidelines from our and our patients experiences. The amount of side effects that you are experiencing has no effect on the result of the treatment. A lot of the experienced side effects are the result of the induced menopause. These side effects could also occur if you have already passed the menopausal stage. Most complaints simmer down after two to three months of endocrine therapy.

1. Hot flashes
2. Dry vagina
3. Loss of libido
4. Loss of ability to concentrate
5. Mood swings
6. Sleeping problems
7. Weight gain
8. Arthralgia
9. Osteoporosis
10. Nausea
11. Thrombosis
12. Fatigue
13. Thinning of hair
14. Skin problems
15. Headaches

Explanation:

- = a side effect or explanation

• = an advice

Hot flashes

• Hot flashes are one of the most common menopausal complaints.
• They create a sensation of heat, often coming from the chest towards the back, arms and head. You could also experience redness in the face and extensive sweating. They can last a few seconds, or several minutes and could happen at any time and any place.
• Distract yourself, if experiencing a hot flash;
• Regular physical exercise helps prevent hot flashes;
• Wear clothes and use bed sheets made from natural cloth, like cotton;
• Ventilate and cool your bedroom;
• Alcohol, smoking, spicy food, caffeine, chocolate, berries, white sugar and stress can cause and/or worsen hot flashes. The sensitivity to one or more of these is different in each patient;
• There is some evidence that acupuncture may help reduce these symptoms.

Dry vagina

• Because of the lower amount of estrogen in the blood, the mucus of the vagina could get thinner and dryer. This can cause pain during sexual intercourse. In rare cases, tamoxifen could cause more discharge.
• Have an open discussion about this and what it means to you with your sexual partner;
• Use lube if necessary, check the ingredients to make sure they do not contain any hormones;
• Stay alert to changes in discharge and smell, this could point to a yeast infection. If so, contact your doctor;
• Don’t wash your vagina with soap, water is sufficient;
• Make sure to practice good personal hygiene;
• If you’re experiencing vaginal bleeding, contact your doctor.

Loss of libido

• Because of the changes in hormone levels, you could experience low libido. Besides the chemical changes, you (and/or your partner) might also need some time to get used to possible changes the breast cancer caused to your body and sexuality.
• Try to talk to each other to find out what you need;
• If you are experiencing problems, you can talk to your doctor. He/she can refer you to a sexologist if necessary.

Loss of ability to concentrate

• Changes in hormone levels could lead to concentration problems and forgetfulness.

Mood swings

• Women going through menopause regularly complain about mood swings, feeling irritable and not very emotionally balanced. Depressive feelings can occur as well. This could be part of the menopause process, but if you are experiencing these feelings on endocrine therapy they could also be the result of the whole process revolving the breast cancer.
• Try listening to your own feelings;
• Talk to your loved ones about how you feel;
• Try connecting with fellow patients for recognition and talks;
• If necessary, discuss these complaints with your doctor. He/she can refer you to a social worker or psychologist for more specialized care.

Sleeping problems

• The combination of sleeping problems and the hot flashes possibly occurring during the night can cause a disruptive sleep pattern. This can cause issues maintaining an active day and could increase irritableness.
• Make a day program with incorporated moments of rest;
• Try not to sleep during the day;
• Discuss with your doctor or nurse practitioner if you need more help.

Weight gain

• During endocrine treatment your weight might increase a few pounds. The specific cause of this is unknown. It could also be caused by fluid retention.
• Try to stay active with regular exercise;
• Watch for excessive sugar and fat intake;
• If necessary, discuss your weight gain with a dietician.

Arthralgia

• Estrogens play a role in the formation of joint fluids. This process could change during endocrine treatment, causing arthralgia. Especially in the morning your joints might be painful and stiff.
• Keep active;
• Warm showers might help for these complaints;
• Discuss your complaints with your doctor when they cause impairments.

Osteoporosis

• All women in menopause experience a decrease in bone density. This is called osteoporosis. For a healthy bone mineral homeostasis, estrogen is essential. After going through menopause, the estrogen levels will have decreased, which could lead to (quicker) loss of bone density and therefore risk of fractures. This risk is most pronounced for women being treated with aromatase-inhibitors and women going through premature menopause.
• It is essential to have enough calcium in your diet. Calcium is most present in dairy products, but also fish, shrimps, bread, legumes and nuts contain calcium. Plant-based calcium is less absorbed than animal-based calcium. You need about 1000-1500 mg of calcium a day, this entails two to three servings of dairy and some cheese. If you can’t have dairy due to dietary restrictions, calcium supplements (combined with vitamin D to ensure better absorption) could be the best option for you.
• Stay physically active, to maintain strong bones. Especially ‘burdened’ exercise (such as walking, fitness, running and dancing) have a positive effect on the production of bone, more so than ‘unburdened’ exercise (such as swimming and biking);
• Maintain a diet containing the daily recommended amount of calcium, as described above;
• Be sure to get enough sunlight to stimulate the manufacturing of vitamin D. This is necessary for absorption of calcium;
• Don’t smoke;
• Try moderating your alcohol intake;
• Based on your personal circumstances and case, your doctor could decide to treat you with medication that will halt the breakdown of your bones.

Nausea

• Nausea, if it occurs, is most likely limited to the beginning of treatment. This will generally wear off four to six weeks after start of treatment.
• If your complaints persist or if you start losing weight because of it (more than 3 kg), discuss this with your doctor or nurse practitioner.
• Drink enough fluids, to a minimum of 1,5 - 2 liter a day. This means 10 to 15 glasses of tea, water, milk, juice, coffee, soup, yoghurt e.g.;
• Try taking your endocrine treatment at a different moment in the day, to see if this changes the complaints;
• Try having multiple smaller meals instead of a few big ones. Having too much food in one go can increase your nausea;
• An empty stomach may also increase nausea, which could also benefit of smaller meals spread out over the day;
• Don’t have meals containing a lot of fat/grease;
• Try minimizing your alcohol intake to see if this effects your nausea;
• Don’t smoke, as this could worsen nausea complaints;
• Make sure to rest enough around the meals, giving your body the chance to recuperate.

Thrombosis

• The use of tamoxifen leads to a slight increased risk to develop thrombosis. This is a bloodclot that gets stuck in a vein, which could eventually block that vein. This inhibits blood from going through that vein freely.
• You can recognize thrombosis through the following symptoms:
  - A red, swollen arm or leg that feels warm and hurts.
  - Shortness of breath and pain when taking deeper breaths.
• Always contact your doctor or nurse practitioner when experiencing these symptoms.

Fatigue

• Because of the changes in your hormonal homeostasis, you could experience more fatigue. This fatigue could also be the result of the cancer itself, the treatment that you may have had prior to the endocrine treatment, and the psychological strain it all might (have) had on you. If the fatigue is indeed caused by your endocrine treatment, it is expected to decrease over the course of time. It is possible it will not resolve completely.
• Being fatigued could lead to loss of functionality throughout the day, sleeping problems, loss of concentration, forgetfulness, being irritable or worrysome.
• Take enough time to rest;
• Try not to sleep during the day to prevent sleeping problems during the night;
• Spread your activities throughout the day and week;
• Try to keep up with physical exercise with 30 min of exercise a day. If this seems too much, you could also split that up in two sessions of 15 minutes;
• Try maintaining regularity in your day-night rhythm;
• Have a healthy, balanced diet;
• Try talking about your complaints and worries to your loved ones;
• Prioritize the things that are most important, and say “no” more often;
• Accept help from loved ones when needed. This gives you more energy for the things you prioritize;
• Discuss your fatigue with your doctor or nurse practitioner.

Thinning of hair

• Endocrine therapy could lead to thinner hair and more hair loss than normal. You will not go bald, such as during chemotherapy.
• Use shampoo for sensitive hair;
• Don’t wash your hair with water that’s too hot;
• Take care in rinsing out all of the shampoo;
• You could use a moisturizing conditioner after shampoo ;
• Dry carefully with a soft towel;
• Comb your hair while it’s still wet, to prevent knots.

Skin problems

• Endocrine therapy can change your skin. It could become dry, flaky or greasy. It could become thicker, or thinner, and lead to redness or spotty skin by differences in pigmentation. It could also be easily irritable. You could experience an increase in facial and body hair.
• Try different skin products based on the changes you experience;
• If you’re experiencing itchy skin, try menthol based crème or powder;
• Consider going to a beautician for advice or assistance.

Headaches

• There is a clear relation between hormonal changes (such as those caused by endocrine treatment) and headaches. The underlying causality of this is unknown.
• If you are experiencing headaches;
• Try relaxing;
• Find something to distract yourself;
• Find calm surroundings;
• When necessary, use painkillers (or anti-migraine medication if you are diagnosed with migraines).

More information

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Practical information

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april 2025