Daidzein effect on hormone refractory prostate cancer in vitro and in vivo compared to genistein and soy extract: potentiation of radiotherapy.

Purpose: Genistein, the major bioactive isoflavone of soybeans, acts as a radiosensitizer for prostate cancer (PCa) both in vitro and in vivo. However, pure genistein promoted increased metastasis to lymph nodes. A mixture of soy isoflavones (genistein, daidzein, glycitein) did not cause increased metastasis, but potentiated radiotherapy.