Breast swelling (gynaecomastia)

What is gynaecomastia?

Gynaecomastia is swelling or enlargement of the breast in men.

What causes breast swelling in men with prostate cancer?

Hormone therapy is a common treatment for prostate cancer. This can change the balance of hormones in your body and cause breast tissue to grow.

What is the treatment for gynaecomastia?

You might have radiotherapy, a drug called tamoxifen or surgery to remove the breast tissue. Talk to your doctor about what is best for you.

Some hormone therapies for prostate cancer can cause breast swelling and tenderness. This is gynaecomastia (pronounced guy-nee-co-mass-tee-ah).

Why does hormone therapy cause breast swelling?

Hormones occur naturally in your body. They control the growth and activity of normal cells. Testosterone is a male sex hormone mainly made by the testicles.

Men also have a small amount of oestrogen circulating around their bodies.

Prostate cancer usually depends on testosterone to grow. Hormone therapy blocks or lowers the amount of testosterone in the body. 

A lower testosterone level changes the balance of hormones in your body. And you have more oestrogen compared to the level of testosterone. Oestrogen stimulates the growth of breast tissue.

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

Before treatment, ask your doctor how likely it is that your breast tissue will get swollen. Breast swelling is more common with some types of hormone therapy. This includes bicalutamide when you take it for longer than 6 months. 

Find out more about hormone therapy for prostate cancer

Treatment for breast swelling

Hormone therapy, 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​

• tablets such as 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

You take tamoxifen as tablets. It 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.

Surgery to remove breast tissue

Surgery to remove extra breast tissue is an option. 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 inverted nipple

• loss of feeling in the breast

Another way to remove 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 on hormone treatment 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 liposuction may work better.