OBJECTIVES:~Primary~Determine the efficacy of Hypericum perforatum (St. John's wort) in alleviating hot flashes, in terms of hot flash frequency, score, and duration and disruption of daily activities caused by hot flashes, in postmenopausal women with non-metastatic breast cancer.~Determine hot flash changes over 4 weeks in patients treated with this drug.~Secondary~Determine the toxicity of this drug in these patients.~Determine the effect of Hypericum perforatum (St. John's wort) on serum tamoxifen levels in women receiving tamoxifen therapy.~Determine the effect of Hypericum perforatum (St. John's wort) on general health-related quality of life and mood at 2 and 4 weeks relative to baseline, and during the 2 week post-treatment phase in these patients.~To evaluate changes in average weekly hot flush scores and duration over course of study.~OUTLINE: This is a multicenter study.~Patients receive oral Hypericum perforatum (St. John's wort) three times daily for 4 weeks in the absence of disease progression or unacceptable toxicity.~Patients complete a daily diary of the frequency, severity, and duration of their hot flashes, and complete quality of life and mood assessments every 2 weeks during study treatment and continuing weekly for 2 weeks after completion of study treatment.~Patients receiving tamoxifen will have blood tests to measure serum tamoxifen levels at baseline, 2, 4, and 6 weeks.~PROJECTED ACCRUAL: A total of 39 patients will be accrued for this study.
RATIONALE: St. John's wort may help relieve hot flashes in women with breast cancer.~PURPOSE: This phase II trial is studying how well St. John's wort works in relieving hot flashes in women with non-metastatic breast cancer.