Breast swelling is sometimes a side effect of hormone treatment for cancer. Treatments are available to help avoid and relieve symptoms.

Some cancer treatments can lower the levels of sex hormones in the body. The sex hormones are oestrogen and progesterone in women, and testosterone in men. The cancer treatments include hormone treatments for prostate cancer.

Prostate cancer needs testosterone to grow. Hormonal treatments aim to:

• stop the testicles from making testosterone
• stop testosterone reaching cancer cells

The adrenal glands produce a small amount of oestrogen in men. Hormonal treatments lower your testosterone and this changes the balance of hormones in your body. When oestrogen becomes higher, compared to the amount of testosterone, breast tissue can develop. Oestrogen stimulates the growth of breast tissue.

Breast swelling in men is gynaecomastia (pronounced guy-nee-co-mass-tee-ah).

Swelling can happen in either breast, or both breasts. It may be painful. It starts as fatty tissue. But it can develop into thicker (dense) tissue. This is glandular tissue.

Risk of breast swelling

Anti androgen treatments, such as bicalutamide, causes swelling in about 1 in 2 (50%) of men. 

It is less likely when taking medicines called luteinising hormone releasing hormone drugs, such as Zoladex.

Treatment for breast swelling

Anti androgen treatments, such as bicalutamide, may last for several years. Your doctor may suggest treatment to reduce the risk of breast swelling if your treatment is likely to be longer than 6 months.

Treatment might include:

• radiotherapy
• tamoxifen
• surgery

Radiotherapy

Radiotherapy uses high energy x-rays to reduce the swelling. It's the main treatment for preventing and treating breast swelling. It is called breast-bud radiotherapy. You have one or two sessions of radiotherapy and it's a very small dose. 

The skin around your nipple may be red and sore for a few weeks after the treatment. There is a small risk of cancer developing in the radiation area many years after treatment. Your doctor will talk to you about this.

Tamoxifen

Tamoxifen works by blocking oestrogen. This slows down breast tissue swelling. Research suggests that in men taking bicalutamide it can:

• prevent breast swelling
• reduce swelling and pain

Tamoxifen can cause side effects such as hot flushes.

It's unclear how tamoxifen might affect how well hormone treatments work for prostate cancer. We need more research to find out. Your doctor might suggest tamoxifen if radiotherapy does not help your breast swelling.

Aromatase Inhibitors (letrozole, exemestane or anastrozole)

Aromatase Inhibitors (AIs) stop the body from changing male hormones into oestrogen in the fatty tissues of the body. We know from research that AIs can reduce breast swelling and pain but we need to know more about exactly how well they work.

Surgery to remove breast tissue

You can have any excess breast tissue removed. The surgeon makes a cut (incision) around the nipple to leave it in place and minimise any scarring.

After surgery you might have:

• bleeding
• flattening around the nipple
• an inpointing nipple (inverted nipple)
• loss of feeling in the breast

Another way of removing breast tissue is to suck out the excess fatty tissue with liposuction. Liposuction works better if the swelling is made up of fatty tissue. Men having hormone treatment for prostate cancer tend to have glandular tissue, which is thicker. Glandular tissue is more difficult to suck out than fatty tissue. 

There is some research that suggests combining surgery with sucking out the fat may work better.

Feelings about breast swelling

Breast swelling and breast pain can be very distressing and difficult to cope with. Many men feel embarrassed and less confident about themselves when they have it.

If you haven’t been offered any advice or treatment about breast swelling, and you notice it starting to happen, tell your doctor or nurse as soon as possible They can work out the best treatment for you and offer support.