Double-Blind Randomized 12-Month Soy Intervention Had No Effects on Breast MRI Fibroglandular Tissue Density or Mammographic Density

Abstract

Soy supplementation by patients with breast cancer remains controversial. No controlled intervention studies have investigated the effects of soy supplementation on mammographic density in patients with breast cancer. We conducted a double-blind, randomized, placebo-controlled intervention study in previously treated patients with breast cancer (n = 66) and high-risk women (n = 29). We obtained digital mammograms and breast MRI scans at baseline and after 12 months of daily soy (50 mg isoflavones per day; n = 46) or placebo (n = 49) tablet supplementation. The total breast area (MA) and the area of mammographic density (MD) on the mammogram were measured using a validated computer-assisted method, and mammographic density percent (MD% = 100 × MD/MA) was determined. A well-tested computer algorithm was used to quantitatively measure the total breast volume (TBV) and fibroglandular tissue volume (FGV) on the breast MRI, and the FGV percent (FGV% = 100 × FGV/TBV) was calculated. On the basis of plasma soy isoflavone levels, compliance was excellent. Small decreases in MD% measured by the ratios of month 12 to baseline levels were seen in the soy (0.95) and the placebo (0.87) groups; these changes did not differ between the treatments (P = 0.38). Small decreases in FGV% were also found in both the soy (0.90) and the placebo (0.92) groups; these changes also did not differ between the treatments (P = 0.48). Results were comparable in patients with breast cancer and high-risk women. We found no evidence that soy supplementation would decrease mammographic density and that MRI might be more sensitive to changes in density than mammography.

Trial registration: ClinicalTrials.gov NCT01219075.

©2015 American Association for Cancer Research.

Figures

Figure 1

CONSORT diagram for study design and availability of mammograms and MRIs at baseline and after 12 months of intervention

Figure 2

Plasma soy isoflavone (genistein and daidzein combined) at baseline and after 12 months of intervention (Red= soy group; green= placebo group) (gndz_0: genistein and daidzein combined at baseline; gndz_1: genistein and daidzein combined at the end of month 12)

Figure 3

(a) Baseline mammographic density percent (MD%) on square-root scale (S_md_1) (square-root scale mammographic density percent at baseline) (x-axis) vs end of 12-month MD% (S_md_2) (square-root scale mammographic density percent at 12-month) (y-axis); and (b) Baseline FGV% on square-root scale (S_mri_1) (square-root scale fibroglandular volume percent at baseline) (x-axis) vs end of 12-month FGV% (S_mri_2) (square-root scale fibroglandular volume percent at 12-month) (y-axis) (s=soy group; p=placebo group).