Testosterone Treatment for Prostate Cancer
- Cancer of the prostate, which is a small gland at the base of the scrotum, is often detected while it is still in the early stages before it has spread, or metastasized, to other organs. It is a slow-growing tumor, and almost all men who are diagnosed and treated remain cancer-free after five years.
- Prostate cancer is a hormone-dependent cancer. The male hormone (or androgen) testosterone stimulates the development of secondary male sexual characteristics, such as body hair, muscle development and prostate growth, during puberty. After puberty, androgens continue to stimulate prostate cells in the adult male. Androgens stimulate all prostate cells and are unable to distinguish between healthy and cancerous cells, thus male hormones serve as fuel to stimulate prostate tumor growth.
- Prostate cancer is commonly treated with hormonal therapy, but that term is misleading. When used as treatment for prostate cancer, hormonal therapy refers to blocking androgen production to starve the tumor, not supplementing testosterone production. Androgen ablation therapy, which is the full name for this treatment, stops the testes from producing testosterone in an effort to slow or halt tumor growth. Androgen ablation therapy is typically administered for six months, followed by a six-month rest period to delay the tumor from developing resistance. Androgen ablation therapy by itself does not eliminate the tumor but prevents it from worsening and boosts the effect of other treatments.
- Testosterone production is blocked by one of four methods. Orchiectomy (surgical removal of the testicles) or chemical castration through the use of luteinizing hormone releasing hormone (LHRH) agonists or LHRH antagonists reduce testosterone production by up to 95 percent. Anti-androgens block testosterone receptors, preventing circulating hormones from interacting with the prostate cells. A combination of anti-androgens and castration reduces the amount of circulating hormone while blocking the action of whatever testosterone remains. Estrogen, or female hormone, reduces testosterone production by confusing the hypothalamus to interrupt the cascade that normally triggers testosterone production. Estrogen is rarely used because of serious cardiovascular effects.
- Although most men experience a noticeable reduction in tumor size after androgen-ablation therapy, all prostate cancers eventually develop resistance to the drastically reduced hormone levels. Some tumors develop resistance within months of androgen-ablation therapy whereas in others, resistance may take years to develop. Treatment options are limited for tumors that become resistant or hormone refractory. Therapy for hormone-refractory prostate cancer may involve a second course of androgen-ablation therapy, which is generally ineffective, or radiation and chemotherapy.
