Hormone Therapy: In Breast and Prostate Cancer

What is it?

Hormone therapy in cancer aims to reduce the oestrogen or androgen signal that the tumour uses to grow. It does not mean destroying the body’s own hormone completely. It should also not be confused with hormone replacement therapy in menopause.

In breast cancer, it is first looked at whether the tumour carries oestrogen and progesterone receptors. If it does not, these drugs have no place. The great majority of prostate cancer is sensitive to the androgen signal. Sensitivity may decrease over time, in which case the plan is updated.

How does it work?

Tamoxifen blocks the oestrogen receptor. Anastrozole, letrozole and exemestane are aromatase inhibitors that reduce oestrogen production after menopause. GnRH analogues such as goserelin can be used to suppress ovarian function.

In prostate cancer, goserelin or leuprorelin lowers testicular androgen. Enzalutamide blocks the receptor and abiraterone stops an enzyme in androgen production. These drugs are considered alone or in sequence, sometimes together with chemotherapy or new-generation drugs.

In which cancers is it used?

The main fields are hormone receptor-positive breast cancer and prostate cancer. It is used to reduce the risk of recurrence after surgery in early stages and to slow growth in metastatic disease. In some types of cancer of the uterine body, hormone drugs may also be discussed.

Which treatment is appropriate is discussed at the tumour board, with the relevant specialties taking part, by considering the type, stage and molecular features of the cancer and the person’s general condition together.

How is it given?

Most drugs are taken by mouth every day. GnRH analogues can be injected under the skin or into the muscle once a month or every three months. Abiraterone is taken on an empty stomach and usually together with a corticosteroid.

In breast cancer, the duration is a few years in most early stages. In metastatic prostate cancer, treatment can continue as long as the response lasts. At check-ups, blood pressure, blood sugar, liver tests and bone health are monitored.

During follow-up, blood tests, imaging and symptom review are read together. The dose or date may be changed according to side effects and organ function. The list of medicines used at home is updated at every visit. Sudden fever, shortness of breath, uncontrolled diarrhoea or bleeding should be reported the same day.

Possible side effects

Hot flushes, joint pain, vaginal dryness, changes in sexual desire, fatigue and mood swings may occur. Aromatase inhibitors can reduce bone density. With prostate-directed treatments there may be hot flushes, bone thinning, loss of muscle mass and breast tenderness.

Sudden swelling in the leg, chest pain or severe headache are assessed the same day. Whether a bone-protecting drug is needed is a separate decision.