Prospective study of soy intake and breast cancer prognosis in Chinese breast cancer survivors

  • Topic:
  • Institution: University of Hong Kong
  • Country: Hong Kong
  • Status: Completed

During the course of this grant, the principal investigator changed from Suzanne Ho to Professor Winnie Yeo, who wrote the final progress report below. Professor Yeo has received a subsequent grant to continue her research in this area, details of which can be found on her grant page.

Scientific abstract

(View plain language abstract)

Background

Survivors of cancer, particularly breast cancer, are highly motivated to seek information about diet, dietary supplement use, and nutritional complementary therapies. Soy foods have generated considerable interest among breast cancer survivors for the alleviation of menopausal symptoms and promoting health; but have also raised much concern because of conflicting reports of soy effects on breast cancer prognosis.

This is a prospective cohort study which aims to examine the effect of habitual dietary soy intake prior to as well as after the diagnosis of breast cancer on breast cancer prognosis and survival.

Hypothesis

Habitual high intake of soy food, both before and after breast cancer diagnosis, does not have an adverse effect on survival among breast cancer survivors, and that there may be a beneficial effect on prognosis, breast cancer recurrence, mortality, and all-cause mortality.

Methods

Recruit and construct a cohort of 1,350 breast cancer patients with initial diagnosis of primary breast cancer.

Obtain baseline information on socio-demographic characteristics, and potential confounding variables including reproductive and disease history, health and lifestyle factors, and use of complementary therapy based on standardized structured questionnaire, and to also obtain anthropometric measurements.

Conduct interviews with structured food questionnaires at diagnosis [baseline], 18- and 26- months post-diagnosis.

Obtain clinical information during follow-up.

Findings

Between January 2011 and January 2014, 2,811 Chinese breast cancer cases were screened from the two major regional hospitals. Among 2,045 eligible subjects, 1,465 cases agreed to participate in the study with a response rate of 72%. By the end of March 2014, all subjects completed the baseline interviews. About 70% of cases were aged between 45 and 64 years, and 71% of subjects were married. Two-fifths (44%) of subjects had completed high school. Three-fifths (59%) of cases were working full-time before diagnosis. Very few subjects were ever smokers (7%) or regular alcohol users (5%).

The first follow-up (18-month) assessment was commenced in February 2012; this was completed in August 2015.
The second follow-up (36-month) assessment commenced in August 2013; 99% of the patients have completed this follow-up. The remaining 14 patients (1%) will be completing this follow-up by August 2017.

Conclusions

Data analysis is currently continuing.

Plain language abstract

Background

Survivors of cancer, particularly breast cancer, are highly motivated to seek information about diet, dietary supplement use, and nutritional complementary therapies. Soy foods have generated considerable interest among breast cancer survivors for the alleviation of menopausal symptoms and promoting health; but have also raised much concern because of conflicting reports of soy effects on breast cancer prognosis.

Aims and objectives

  1. To evaluate the association of soy food intake prior to breast cancer diagnosis with outcomes in breast cancer recurrence, mortality, and all-cause mortality among breast cancer survivors.

  2. To evaluate the relationship between post-diagnosis soy food intake with outcomes in breast cancer recurrence, mortality, and all-cause mortality among breast cancer survivors.

How the study was carried out

Newly diagnosed breast cancer patients were recruited. Clinical information including baseline demographics were obtained. Patients were interviewed with structured questionnaires that included assessment of soy intake.

Key findings and conclusions

Data analysis is ongoing.