RATIONALE: Exercising regularly may lower the risk of breast cancer.

PURPOSE: This randomized clinical trial is studying how well exercise prevents breast cancer in healthy young women.

OBJECTIVES:

Primary

• Compare the changes in urine levels of a stable marker of oxidative stress (F_2-isoprostanes) in healthy young women who undergo exercise training during 4 menstrual cycles vs no exercise.

Secondary

• Assess the changes in other metabolic factors that explain the association between physical activity and breast cancer, including:

Estrogen metabolism (estrone, estradiol, estriol, 2-OHE_1, 2-OHE_2, 2-MeOHE_1, 2-MeOHE_2, 4-OHE_1, 4-OHE_2 [as well as ratios of these metabolites], insulin-like growth factor (IGF)-1 (as well as IGF-binding proteins-1, -2, and -3, insulin, glucose, body composition (including body mass index, lean mass, and body fat [DEXA scan]).

OUTLINE: This is a randomized, controlled study. Participants are stratified according to baseline body fat percentage and age (18 to 24 years vs 25 to 30 years). Participants are randomized to 1 of 2 intervention arms.

• Arm I: Participants exercise for 30 minutes 5 times a week. The intensity of exercise is increased every 4 weeks. The exercise regimen continues for up to 4 menstrual cycles.
• Arm II: Participants are observed for 4 menstrual cycles. Participants in both arms undergo 24-hour collection of urine on days 7, 8, and 9 of menstrual cycles 1 and 6. F_2-isoprostanes are measured via gas chromatography-mass spectrometry (GC/MS). Estrogens are also measured by GC/MS and include E_1, E_2, E_3, 2-OHE_1, 2-OHE_2, 4-OHE_1, 4-OHE_2, 2-MeE_1, 2-MeE_2, 4-MeE_1, 4-MeE_2, and 16OHE_1.

Participants undergo blood collection, body mass measurement by dual-energy x-ray absorptiometry, and a fitness assessment twice during the 6-month study.

PROJECTED ACCRUAL: A total of 400 participants will be accrued.

Inclusion Criteria:

• Healthy women
• Self-reported menstrual cycle length of 25-35 days within the past 2 months
• Nonsmoker
• Sedentary (exercise < 3 times weekly within the past 6 months)
• Intact ovaries and uterus
• No history of gynecological problems (e.g., fibroids, endometriosis, polycystic ovary syndrome)
• Female
• Premenopausal
• Body mass index 18.5 to 40
• Stable weight (no changes ≥ 10% within the past year)

Exclusion Criteria:

• No pregnancy or breast feeding within the past 6 months

• No plans to become pregnant during study treatment

• No cancer within the past 5 years except for nonmelanoma skin cancers

• No medical condition that would prohibit participation in a vigorous program of weight-bearing aerobic exercise including, but not limited to, any of the following:

  • Fibromyalgia
  • Chronic fatigue syndrome
  • Metabolic disorders
  • Recent cardiovascular event
  • Orthopedic limitations
  • Psychiatric disorders requiring antipsychotic drugs

• No uncontrolled hypertension (systolic blood pressure [BP] > 160 mm Hg and/or diastolic BP > 99 mm Hg)

• No more than 7 alcoholic beverages per week

• No injected hormonal contraceptive use within the past year

• More than 6 months since prior use of intrauterine device

• More than 3 months since prior oral or patch hormone contraceptives

• No medication that would prohibit participation in a vigorous program of weight-bearing aerobic exercise