[Lani]

I had been under the impression that whether or not soy might increase or decrease the chance of recurrence of bc was related to ER/PR status but now two studies one out of Japan and one out of Korea (below) say soy's effect on recurrence more likely depends on tumor's her2 status. The article below is based on a small number of patients, but the full article refers to the Japanese study and is very interesting...

Nutr Cancer. 2012 Jan 2. [Epub ahead of print]
Differential Influence of Dietary Soy Intake on the Risk of Breast Cancer Recurrence Related to HER2 Status.
Woo HD, Park KS, Ro J, Kim J.
Source
a Cancer Epidemiology Branch, National Cancer Center , Korea.
Abstract
The effects of soy products and isoflavone on breast cancer recurrence were compared according to receptor status including epidermal growth factor receptor-2 (HER2) with 339 Korean women. Dietary intake of soy foods was assessed using a validated food frequency questionnaire with 103 food items. Twenty-five patients experienced breast cancer recurrence, 17 patients were HER2 negative, and 8 patients were HER2 positive. Legume intake (mostly from black soybeans) was inversely associated with the risk of breast cancer recurrence in HER2 negative cancer patients (HR: 0.27, 95% CI: 0.13-0.57, P for trend < 0.01), whereas legume intake was positively associated in HER2 positive cancer patients (P for trend = 0.02). In HER2 negative cancer patients, isoflavone was inversely associated with breast cancer recurrence (HR: 0.23, 95% CI: 0.06-0.89; P for trend = 0.01). Total soy intake was not associated with an increased risk of cancer recurrence. In conclusion, overall soy food intake might not affect the risk of cancer recurrence, but high intake of soy isoflavones increased the risk of cancer recurrence in HER2-positive breast cancer patients. However, further research is needed to confirm these results due to the small number of cancer recurrence events.
PMID: 22211813