RATIONALE: A diet that is low in fat and/or high in flaxseed may slow or prevent disease progression of prostate cancer.

PURPOSE: Randomized phase II trial to study the effectiveness of a diet that is low in fat and/or high in flaxseed in slowing or preventing disease progression in patients who have newly diagnosed prostate cancer.

OBJECTIVES:

• Compare tumor proliferation in patients with newly diagnosed prostate cancer eating fat- and/or flaxseed-modified diets.
• Compare differences in histopathological markers associated with prostate cancer (rates of apoptosis, extent of high-grade prostatic intraepithelial neoplasia) among patients in these diet groups.
• Compare changes in serum prostate specific antigen among patients in these diet groups.
• Compare changes in hormone-related factors (total serum testosterone and free androgen index, insulin-like growth factor [IGF], and IGF-binding protein-3) among patients in these diet groups.
• Compare the effects of diet on nutritional biomarkers (levels of lignans in the urine and ejaculate, fatty acid profiles of erythrocytes and prostatic tissue) in these patients.
• Determine associations between dietary modification and changes in dietary biomarkers, hormonal intermediates, and study endpoints in these patients.

OUTLINE: This is a randomized study. Patients are stratified according to Gleason score (less than 7 vs at least 7) and race (black vs non-black). Patients are randomized to 1 of 4 diet groups.

• Arm I (Flaxseed-supplemented diet): Patients are instructed to incorporate ground flaxseed into their daily diets.
• Arm II (Low-fat diet): Patients are instructed on ways to achieve a diet with no greater than 20% of total energy from dietary fat.
• Arm III (Flaxseed-supplemented, low-fat diet): Patients are instructed as in arm I and arm II.
• Arm IV (Control diet): Patients are contacted weekly, but do not receive dietary counseling until after surgery.

All patients ingest the diets for at least 3 weeks and complete diet diaries until surgery. After surgery, all patients receive dietary counseling.

PROJECTED ACCRUAL: A total of 160 patients (40 per treatment arm) will be accrued for this study.

DISEASE CHARACTERISTICS:

• Histologically confirmed prostate cancer
• At least 3 weeks until planned prostatectomy (24 days between day 1 visit and surgery)
• Current diet that provides more than 30% of calories from fat

PATIENT CHARACTERISTICS:

Age

• 18 and over

Performance status

• Not specified

Life expectancy

• Not specified

Hematopoietic

• Not specified

Hepatic

• Not specified

Renal

• Not specified

Other

• Mentally competent
• Able to speak and write English
• Must have telephone access

PRIOR CONCURRENT THERAPY:

Biologic therapy

• Not specified

Chemotherapy

• Not specified

Endocrine therapy

• No concurrent hormonal therapy

Radiotherapy

• Not specified

Surgery

• At least 2 weeks since prior prostate biopsy

Other

• At least 7 days since prior antibiotics
• No prior therapy for prostate cancer
• No concurrent dietary supplements initiated within the past 3 months or anticipated to begin during study except standard multivitamin/mineral preparations (e.g., One-A-Day, Theragran, or Centrum) that do not supply > 100% of the recommended daily allowance of any vitamin or mineral
• No other concurrent neoadjuvant therapies
• No other concurrent flaxseed consumption