Isoflavones and Radiation Therapy in Treating Patients With Localized Prostate Cancer

Phase II Randomized Study of Soy Isoflavones in Patients With Localized Prostate Cancer Treated With Radiation Therapy

RATIONALE: Eating a diet high in soy foods may slow the progression of some types of cancer. Isoflavones are compounds found in soy food that may slow the growth of prostate cancer cells and prevent further development of prostate cancer. Radiation therapy uses high-energy x-rays to kill tumor cells. Giving isoflavones together with radiation therapy may be an effective treatment for prostate cancer. PURPOSE: This randomized phase II trial is studying the side effects and how well giving isoflavones together with radiation therapy works in treating patients with localized prostate cancer.

OBJECTIVES: Determine the effect of soy protein isolate (isoflavones) and radiotherapy on the modulation of biomarkers in patients with localized prostate cancer. Determine the toxicity of this regimen in these patients. Determine the effect of this regimen on the quality of life of these patients. OUTLINE: This is a randomized, placebo-controlled study. Patients are randomized to 1 of 2 treatment arms. Arm I: Patients receive oral soy protein isolate (isoflavones) twice daily for 6 months in the absence of disease progression or unacceptable toxicity. Arm II: Patients receive an oral placebo twice daily for 6 months in the absence of disease progression or unacceptable toxicity. In both arms, patients also undergo radiotherapy while receiving isoflavones or placebo. Quality of life is assessed periodically. PROJECTED ACCRUAL: A total of 70 patients will be accrued for this study.

Toxicity as measured by number and grade of adverse events weekly during radiation and at 3 and 6 months

DISEASE CHARACTERISTICS: Histologically confirmed adenocarcinoma of the prostate that is localized to the prostate gland Must be scheduled to receive curative radiotherapy for prostate cancer Not eligible for a higher priority study at the Karmanos Cancer Institute PATIENT CHARACTERISTICS: Performance status 0-3 Life expectancy Not specified Hematopoietic Not specified Hepatic Not specified Renal Not specified Other No organ function restrictions PRIOR CONCURRENT THERAPY: Chemotherapy No prior chemotherapy Endocrine therapy No prior hormonal therapy Radiotherapy See Disease Characteristics Other No other concurrent micronutrient supplements, herbs, or vitamins except 1 daily multivitamin