Cancer of the prostate, a male sex gland located near the bladder and rectum, is a type of cancer that occurs commonly in older men. Treatment for prostate cancer depends on the stage of disease (extent of disease at the time of diagnosis), and may include surgery, radiation therapy, hormone therapy, chemotherapy, and/or biologic therapy to help the immune system fight the cancer.
Patients with metastatic prostate cancer have cancer that has spread beyond the area of the prostate and is incurable. The goal of treatment is palliation and improvement in quality of life. Growth of prostate cancer, at least initially, is dependent on the presence of the male hormone testosterone. Depriving the cancer of testosterone is often the initial treatment for patients with metastatic prostate cancer. This can be accomplished by surgical castration (orchiectomy) or the administration of drugs such as flutamide or bicalutamide which interfere with the function of testosterone and other androgenic hormones. Most patients will have a slowing or cessation of cancer growth after hormonal treatment but 80 % of patients will have cancer progression within 12-18 months. These patients are said to have “hormone refractory” prostate cancer.
Chemotherapy is sometimes administered to patients following failure of hormonal therapy although there is controversy over whether or not such treatment prolongs survival. There is however agreement that chemotherapy can alleviate some of the symptoms of prostate cancer growth such as pain and improve performance. Many of the chemotherapy regimens that have been used to treat hormone refractory prostate cancer include estramustine which is an alklyating agent that can be given my mouth. Some of the drugs that have been added to estramustine include etoposide, vinblastine, paclitaxel and docetaxel. Another drug combination that has palliative effects in hormone refractory prostate cancer is mitoxantrone and prednisone. The disadvantages of these regimens is that they frequently cause low blood counts and other toxicities and many have to be given intravenously.
Doctors in Italy have evaluated an oral regimen of cyclophosphamide and estramustine for the treatment of 32 patients with hormone refractory prostate cancer. The average age of these 32 patients was 74 years. Toxicity was mild and mainly gastrointestinal.
Prostate specific antigen (PSA) decreased by at least 50% in 44% of patients, remained stable in 38% and rose in 18%. Seven of 8 patients with bone pain had complete disappearance of pain and one had partial relief. The average duration of response to treatment was 30 weeks.
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Thus, a regimen of estramustine and cyclophosphamide appears to be safe and effective palliative treatment for some patients with hormone refractory prostate cancer. (Cancer, Vol 88, Issue No 6, pp 1438-1444, 2000)
Radiation therapy involves the directing of high-energy X-rays to the affected area of the body, to kill cancer cells. If radiation is selected as the form of treatment for prostate cancer it is important to know that there are variations in the manner in which radiation is delivered which can affect outcomes of treatment.
Doctors at the Cleveland Clinic Foundation evaluated 1041 consecutive patients with localized prostate cancer who were treated with external beam radiation therapy. They divided up the patients into those who received a below average or above average radiation dose of 72Gy. Patients receiving radiation doses above the average had a five year survival of 87% compared to 55% for patients receiving below average radiation doses. Clinical relapses occurred in 5% of patients receiving higher than average radiation doses compared to 12% of patients receiving lower than average radiation doses.
Based on these results these doctors were able to recommend radiation doses based on risk of relapse for 6 subgroups of patients with the lowest risk patients receiving 70-73 Gy and the highest risk groups receiving 80-90 Gy with an intermediate risk group receiving 75-85 Gy. These risk groups are determined by the level of PSA and the Gleason score obtained by looking at the cancer under the microscope.
In order to deliver high doses of radiation therapy without excessive toxicities a technique called three-dimensional conformal radiation therapy is used. This allows radiation to be delivered more accurately to the cancer while sparing normal tissue. It is estimated that less than half the patients receiving radiation therapy for prostate cancer are treated with three-dimensional conformal radiation therapy. (International Journal of Raniation Oncology Biology and Physics, vol 46, Issue No 3 pages 567-574, 2000)
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