Prostate cancer refers to cancer that begins in the male prostate. Metastatic prostate cancer refers to cancer that began in the prostate and extended or spread to another part of the body, distinct from the prostate. Because prostate cancer is typically a slow-growing cancer, it often takes several years for the cancer to become large enough to infiltrate the bloodstream and be carried to other body parts, where secondary tumors can begin to grow. Early detection can help prevent this metastasis. Once prostate cancer metastasizes to other parts of the body, it is no longer curable, although it is treatable to extend and/or improve quality of life.
Treatments
Because metastatic prostate cancer is not curable, treatment is designed to slow the growth of both the primary and secondary cancers, and to improve quality of life. The treatments for metastatic prostate cancer have not evolved dramatically since the 1940s, and largely involve blocking testosterone. Since prostate cancer uses testosterone to grow, blocking testosterone production can inhibit or slow the growth of the cancer cells. Approximately 80 percent of men diagnosed with metastatic prostate cancer respond, at least temporarily, to hormone treatment. However, in 50 percent of those who respond, the cancer eventually mutates within three years and ceases to respond to hormone therapy.
Surgical Hormonal Therapy
Hormone therapy, to reduce the production of testosterone and slow the growth of prostate cancer, can include the surgical removal of the testicles. Since the testicles produce testosterone, removing them surgically inhibits or stops your body's production of testosterone, slowing the growth of the cancer. Because this treatment is not chemotherapy, you experience none of the traditional side effects associated with chemotherapy. However, you may experience a loss of libido, impotence, hot flashes, muscle weakness or osteoporosis.
Injectible Hormone Therapy
If men do not wish to have their testicles removed, physicians may perform hormone therapy using an injection of a medication to inhibit the production of testosterone. Lupron and Zoladex are medications used for this purpose. Your doctor must administer the injection every three months. While this medical inhibition of testosterone production has many of the same side effects of surgical castration, its effects are reversible.
Androgen Blockage
Androgen-blocking drugs remove the final remaining source of testosterone from the body. While 95 percent of testosterone in your body is produced in the testicles, the adrenal glands produce 5 percent of your body's testosterone. Thus, total androgen blockage involves blocking the adrenal androgens from producing hormones. The benefits of this remain unproven, although some studies suggest that this therapy may extend survival time by up to six months. Androgen blockers are generally used in conjunction with other hormonal therapies.
Treating Metastases
Because metastatic cancer, by definition, involves secondary tumors in other parts of your body, your doctor may also treat these sites. The bones are a common site of metastases for prostate cancer. Cancer cells located within the bone can be treated by radiation that targets these secondary tumors, or by a bone-targeting agent called bisphosophonates, which help to slow the processes of bone growth and destruction that are sped up by the metastatic cancer cells' presence in the bones.
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