Hormone Therapy for Prostate Cancer

Male sex hormones are called androgens. They control the growth and upkeep of male characteristics. The most common androgens are testosterone and dihydrotestosterone (DHT). Androgens are needed for the normal prostate to work. They are also needed for prostate cancers to grow.

Early on, prostate cancers need androgens to grow. Hormone therapy lowers androgen levels, or blocks what androgens do. Either way, it slows the growth of these cancers.

Hormone therapy works by cutting off the androgens that prostate cancer needs to grow.

Prostate cancers that still depend on androgens are called castration sensitive. You may also see them called androgen dependent or hormone sensitive. Hormone therapy can slow them.

But most prostate cancers eventually stop responding. They become castration resistant. That means they keep growing even when androgen levels in the body are extremely low. Some newer hormone therapies are available to treat cancer that has become castration resistant.

Hormone therapy can block the production or use of androgens in several ways:

Reducing androgen production by the testicles. This is the most common form. It is called androgen deprivation therapy (ADT), and it is usually the first type people receive. It includes:

• Orchiectomy, surgery to remove both testicles, which can lower testosterone by 90% to 95%. This is permanent.
• LHRH agonists, drugs that eventually cause the pituitary gland to stop signaling the testicles to make androgens. This is called medical or chemical castration and is reversible. They are given by injection or implant. When first started, they can briefly raise testosterone (a "testosterone flare").
• LHRH antagonists, another form of medical castration that does not cause a flare.

Blocking the action of androgens (androgen receptor blockers). These compete with androgens to bind to androgen receptors. That keeps androgens from fueling cancer growth. They are usually used with ADT. They are given as pills.

Blocking androgen production throughout the body (androgen synthesis inhibitors). These stop androgen production by the testicles. They also stop it in the adrenal glands and in prostate cancer cells. They are given as pills.

Hormone therapy may be used in several ways for castration-sensitive prostate cancer:

• Early-stage cancer with higher risk of recurrence. Men having radiation for early-stage cancer with an intermediate or high risk of recurrence often receive ADT as well.
• Relapsed or recurrent cancer. Hormone therapy is often used alone after a recurrence following radiation or surgery.
• Advanced or metastatic cancer. ADT was long the standard, but men are now often treated with ADT plus another hormone therapy or chemotherapy.
• Easing symptoms. Hormone therapy is sometimes used alone to prevent or relieve local symptoms in men who are not candidates for surgery or radiation.

Is the hormone therapy working? Men who take it for more than a few months are tested regularly for the level of PSA (prostate-specific antigen) in their blood. A rising PSA may mean the cancer has started growing again, or has become resistant.

Androgens affect many organs, so ADT can cause a wide range of side effects. They include loss of interest in sex, erectile dysfunction, hot flashes, loss of bone density and fractures. They also include loss of muscle mass and strength, changes in blood fats, insulin resistance, and weight gain. Mood swings, fatigue, and growth of breast tissue are on the list too. The risk goes up the longer you are on hormone therapy.

Some side effects can be reduced. Men who lose bone mass may be prescribed drugs to slow or reverse it. Exercise may help with bone loss, muscle loss, weight gain, fatigue, and insulin resistance. Most sexual and emotional side effects eventually go away if hormone therapy is stopped. But for older men, or those treated for a long time, some changes may not fully disappear. Physical changes such as bone loss may remain.

Many side effects ease after hormone therapy stops, and exercise and certain medicines can help along the way.

• Call 911 or go to an emergency department if pain or pressure grips your chest, or you are suddenly short of breath. The same goes for a droop or weakness on one side, or trouble getting words out. Some research links hormone therapy with a higher risk of heart attack and stroke, though not every study agrees, so these signs are not worth waiting on.
• Call your care team the same day if a small fall or a minor knock leaves you with sharp pain in your back, hip, or ribs. Bone thinned by hormone therapy breaks more easily than you would expect.
• Call your care team within a day or two if low mood, hot flashes, or fatigue start to shape your days. Each of these has treatments, and you do not have to sit them out.

Source: American Cancer Society: hormone therapy for prostate cancer.