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According to a recent article published in the Journal of the American Medical Association (JAMA), high doses of radiation therapy reduce the risk of a cancer recurrence more effectively than conventional doses in early prostate cancer.

The prostate is a gland of the male reproductive system. It produces some of the fluid that transports sperm during ejaculation. After skin cancer, prostate cancer is the most common form of cancer diagnosed in men. For men whose cancer has not spread outside of the prostate, treatment often includes radiation therapy to the prostate and surrounding tissues.

Although radiation for early prostate cancer can result in high rates of long-term, cancer-free survival, cancer will recur in a significant portion of men. Recurrences of prostate cancer are often measured by elevated levels of prostate-specific antigens (PSA) in the blood. Prostate-specific antigens are small proteins that are normally shed by the prostate; however, when PSA levels are elevated, it is often a sign of the presence or recurrence of cancer or other benign conditions related to the prostate. Researchers are evaluating ways in which to minimize rates of recurrences in this patient population.

Researchers from the US recently conducted a clinical trial to directly compare high doses of radiation therapy to conventional doses in the treatment of early prostate cancer. This trial included 393 men with early prostate who were treated between 1996 and 1999 with either high-dose conformal radiation therapy or conventional-dose external beam radiation therapy.

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At approximately 5 years follow-up, cancer recurrences as determined by rising PSA levels were reduced by approximately half in men treated with higher doses of radiation therapy compared to those treated with conventional doses. Rates of recurrence were nearly 40% in men treated with conventional doses, compared with only 20% for those treated with higher doses. At 5 years, survival between the two groups has remained similar. Severe rates of rectal or urinary side effects have occurred in less than 2% of patients in each group.

The researchers concluded that higher doses of radiation therapy appear to more effectively reduce the risk of a cancer recurrence than conventional doses as evidenced by rises in PSA levels in early prostate cancer. Patients with early prostate cancer may wish to speak with their physician regarding their individual risks and benefits of increased doses of radiation therapy.

Reference: Zietman A, DeSilvio M, Slater J, et al. Comparison of conventional-dose vs high-dose conformal radiation therapy in clinically localized adenocarcinoma of the prostate. Journal of the American Medical Association. 2005; 294:1233-1239.