“This is the largest study to date and the only one to have included women taking agents such as tamoxifen to reduce estrogen’s effect on cancer growth”, said the study’s lead author, Cheryl L. Rock, Ph.D., a professor in the Department of Family and Preventive Medicine at the University of California, San Diego.
Participants from this study were drawn from the larger Women’s Healthy Eating and Living Study (WHEL), a dietary intervention trial that followed 3,088 women who had been treated for early stage breast cancer but who were cancer-free at the time they enrolled. Participants were randomly assigned to one of two groups – one that ate a “normal” healthy diet and the other that ate extremely high amounts of fruits, fiber, and vegetables – and were followed for more than seven years. Breast cancer recurrence was about the same in each group.
In the current nested case-control study, 153 WHEL participants whose cancer had recurred were matched with 153 participants who remained cancer-free. These pairs were alike in terms of tumor type, body size, age, ethnicity, use of chemotherapy and other variables. Two-thirds of the participants were using tamoxifen, Rock said. When they enrolled, researchers tested the women’s blood for concentrations of the steroid hormones estradiol and testosterone. They analyzed different forms of estradiol and testosterone in the blood, such as how much was bound to transport proteins and how much was “free” circulating and able to enter a cell.
Researchers found that higher estradiol concentrations, in all forms, significantly predicted cancer recurrence. Overall, women whose cancer came back had an average total estradiol concentration that was more than double the average for women who remained cancer-free. Increased levels of testosterone or the sex hormone binding globulin (SHBG) levels were not associated with recurrence, contradicting the findings of several previous studies.
MEDICA.de; Source: American Association for Cancer Research