Participants undergoing dietary intervention were given a fat gram goal by dietitians. Self-monitoring was carried out using a "keeping score" book.
The findings of the study were presented at the 2014 San Antonio Breast Cancer Symposium - a 5-day conference aiming to provide state-of-the-art information on breast cancer research to an audience of researchers and physicians from over 90 countries.
"The current findings with respect to long-term influence of dietary lifestyle intervention on overall survival are mixed, but of potential importance," reports Dr. Rowan Chlebowski, a medical oncologist from the Harbor-UCLA Medical Center in Torrance, CA.
The study utilized data taken from the Women's Intervention Nutrition Study (WINS), a randomized trial that had previously been used to test whether dietary intervention can improve the clinical outcome of women with breast cancer, and assessed death rates after 15 years of follow-up.
"In a prior report of WINS after 5 years follow-up, relapse events were 24% lower in the intervention group. In the current report, the intervention influence on long-term survival was examined," explains Dr. Chlebowski.
For the current study, the researchers followed 2,437 women aged 48-79 with early-stage breast cancer who received standard-of-care treatment at one of 39 centers in the US. Within 6 months of diagnosis, the participants were assigned to either a control group or a dietary intervention group, whereby fat intake was lowered for 5 years while adequate nutrition was maintained.
Within the intervention group, dietitians assisted participants in implementing a low-fat eating plan. Each woman underwent eight bi-weekly individual counseling sessions, with subsequent follow-ups every 3 months. Fat intake was externally monitored with annual unannounced telephone recalls, as well as self-monitored.
Dietary intervention potentially beneficial for triple-negative breast cancer patients
Commenting on their findings, Dr. Chlebowski says:
"Overall, while the death rate was somewhat lower in the intervention group compared with control group (13.6% versus 17%, respectively), the difference was not statistically significant. However, in exploratory subgroup analyses, in women with estrogen receptor (ER)-negative cancers, a 36%, statistically significant reduction in deaths was seen in women in the intervention group."
Some forms of breast cancer have hormone receptors - proteins that pick up signals from hormones promoting cell growth. These signals can then promote the growth of cancer cells. Around 2 out of every 3 cases of breast cancer test positively for hormone receptors.
Death rate reduction was found by the researchers to be even more significant - at 56% - in women whose breast cancer was both ER-negative and progesterone receptor (PR)-negative.
Among the participants, 1,597 women had ER-positive breast cancer, 478 had ER-negative breast cancer and 362 had ER/PR-negative breast cancer.
Breast cancer can also contain a protein called human epidermal growth receptor 2 (HER2) that promotes the growth of cancer cells. HER2-positive breast cancers are commonly more aggressive than other forms of breast cancer.
"HER2 evaluation was not available when this study was conducted," states Dr. Chlebowski, "but it is likely that a substantial number of ER/PR-negative breast cancers were also negative for HER2, making them triple-negative breast cancers, which generally have a poor prognosis." Further research will be needed to confirm this hypothesis.
Dr. Chlebowski hopes that the study's findings - that dietary intervention could make a difference for women with certain forms of breast cancer - could influence this group of patients to make a lifelong change.
Last month, Medical News Today reported on research from the International Agency for Reseach on Cancer that found nearly half a million new cancer cases per year can be attributed to high body mass index.