Prostate cancer is one of the most common cancers in the United States, according to the Prostate Cancer Foundation. Male hormones stimulate the growth of prostate cancer cells, so one treatment option is to drastically reduce the levels of circulating hormones and essentially starve the cancer. However, some tumor cells grow even in the absence of hormones, or the tumor becomes accustomed to the low hormone levels. The result is hormone refractory prostate cancer, in which the tumor stops responding to hormone deprivation therapy and resumes growth.
Prostate Cancer
is the most common type of cancer after skin cancers, affecting approximately one in six men in the United States. A man is more likely to be diagnosed with prostate cancer than a woman is to be diagnosed with breast cancer, according to the Prostate Cancer Foundation. Fortunately, prostate cancer is associated with one of the highest five-year survival rates of all cancers, primarily because it is often diagnosed when it is still in an early stage. Nearly all men diagnosed with prostate cancer are cancer-free five years after diagnosis.
Hormones and Prostate Cancer
The prostate, a small, walnut-sized organ near the scrotum, manufactures approximately 90 percent of male hormones, or androgens. The other five percent is made by the adrenal glands. The male hormone testosterone causes the prostate gland and other sex organs to grow during puberty, and it contributes to prostate growth through adulthood. Testosterone stimulates all prostate cells; it cannot distinguish between healthy cells and cancerous ones. The presence of testosterone "feeds" prostate cancer cells and stimulates the tumor to grow.
What Is Hormone Refractory Prostate Cancer?
Because male hormones feed the growth of prostate cancer cells, depriving the body of androgens slows or even halts prostate tumor growth. Most men with prostate cancer experience a significant response after hormone deprivation (also called androgen ablation) begins. Hormone therapy is most effective when prostate cancer is in the earliest stages. Unfortunately, the effects of hormone therapy do not last. Prostate cancer cells stop responding after months or even years of hormone deprivation and resume growing. Some prostate cancer cells grow independent of testosterone while others become accustomed to the reduced hormone levels. Prostate cancer that no longer responds to hormone therapy is termed hormone refractory prostate cancer. Hormone refractory prostate cancer is a more advanced stage of prostate cancer.
Hormone Therapy
Hormone therapy may be used alone or combined with other types of treatments. Hormone therapy falls into four types: castration, either by surgical removal of the testicles (orchiectomy) or chemically blocking the hormones that stimulate testosterone production; estrogen (female hormone) therapy, which has no effect on prostate cancer cells but stops the hypothalamus from producing gonadotropin-releasing hormone, which stimulates testosterone production; anti-androgens, which block the receptors on the cells so that testosterone cannot cause the cells to grow; and combination androgen blockade, which combines castration with anti-androgen therapy.
Treatment for Hormone Refractory Prostate Cancer
Treatment for hormone refractory prostate cancer is limited. Hormone therapy may be interrupted for a brief period and then restarted. This strategy may shock the tumor and again slow or halt its growth. Other treatment options for hormone refractory prostate cancer include radiation therapy, chemotherapy or experimental therapies such as immunotherapy, gene therapy, programmed cell death or regulation of the cell signaling process.
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