Long-term endometrial and breast safety of a specific, standardized soy extract

Abstract

Objective To assess the effects of an oral soy isoflavone extract (Phytosoya) on endometrium and breast in postmenopausal women treated for 3 years. Methods A total of 395 postmenopausal women were included in this international prospective, open-label study. The number of patients who completed the 3-year study was 197. The women were treated for 3 years with a specific, standardized soy isoflavone extract (total 70 mg/day). Endometrial biopsy, transvaginal ultrasonography and mammography were performed before and after 3 years of treatment. Results No case of hyperplasia/cancer was diagnosed among the 192 interpretable biopsies at 3 years. Only one case of simple hyperplasia was diagnosed among 197 post-baseline interpretable biopsies. The endometrial safety of this extract has been demonstrated (point estimate 0.5%). There was no statistically significant change in endometrial thickness after 3 years (98.4% inactive or atrophic and 0.3% proliferative endometrium at 1 year). Mammography results showed no notable change from baseline. No patient in any set developed an ACR classification of 4 or 5 after 3 years of treatment. The global safety was rated as either 'excellent' or 'good' by 99.1% of investigators and 99.0% of patients after 3 years of treatment. The adverse events were as follows: eight patients had metrorrhagia and seven patients had at least one breast adverse event: three patients had 'breast pain', two patients reported 'breast tenderness' and two patients h…