Diindolylmethane (DIM), a bioactive metabolite found in cruciferous vegetables such as broccoli, brussel sprouts and cauliflower, may reduce the risk of development or recurrence of breast cancer. There is limited evidence of clinically relevant activity of DIM or long-term safety data of its regular use.
[Photo: Dr. Cynthia A. Thomson]
In a study led by researchers at the University of Arizona Mel and Enid Zuckerman College of Public Health and UA Cancer Center, a randomized, double-blind, placebo-controlled trial was conducted to determine the activity and safety of combined use of BioResponse DIM® (BR-DIM) with tamoxifen. The study “Arizona: A randomized, placebo-controlled trial of DIM for breast cancer biomarker modulation in patients taking tamoxifen,” was first published online in the journal Breast Cancer Research and Treatment, on May 30.
Women prescribed tamoxifen (n = 130) were randomly assigned oral BR-DIM at 150 mg twice daily or placebo, for 12 months. The primary study endpoint was change in urinary hydroxyestrone ratio. The investigators also looked at changes in 4-hydroxyestrone (4-OHE1), serum estrogens, sex hormone-binding globulin (SHBG), breast density, and tamoxifen metabolites.
A total of 98 women (51 placebo, 47 DIM) participated in the clinical trial. Compliance with treatment was more than 91 percent. BR-DIM increased the 2/16α-OHE1 ratio compared to placebo. Serum SHBG increased with BR-DIM compared to placebo. No change in breast density measured by mammography or by MRI was observed. Plasma tamoxifen metabolites were reduced in women receiving BR-DIM versus placebo. Minimal adverse events were reported and did not differ by treatment arm.
The results show that patients taking tamoxifen for breast cancer, daily BR-DIM promoted favorable changes in estrogen metabolism and circulating levels of SHBG. The finding suggest that further research is warranted to determine whether BR-DIM associated decreases in tamoxifen metabolites, including effects on endoxifen levels, reduces the clinical benefit of tamoxifen.