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Researchers have indicated that postmenopausal women who experience 5% or more weight loss have a lower risk of invasive breast cancer than women whose weight remains stable.
The data analysis of the large prospective prospective study on women's health (WHI) shows that, in postmenopausal women who have experienced ≥ 5% weight loss over a 3 year period – intentional or not – the Breast cancer risk was 12% lower than that of women whose weight remained the same.
The study, led by Rowan T. Chlebowski, MD, PhD, Hope City National Medical Center, Duarte, Calif., Was published online Oct. 8 in Cancer. The study was presented in part at the San Antonio Breast Cancer Symposium on December 8, 2017 and was reported by Medscape Medical News at this moment.
"These results suggest that interventions in postmenopausal women aimed at generating weight loss could lead to a reduction in the risk of breast cancer," write the authors.
They note that about one-third of menopausal women in the United States are obese and that obesity is an established risk factor for postmenopausal breast cancer.
Although the analysis found no association between weight gain of ≥ 5% and increased risk of breast cancer (risk ratio [HR], 1.02), a weight gain of ≥ 5% was associated with a significant increase in the risk of triple negative breast cancer (HR, 1.54).
The observation plan of the study "excludes causal inference," say the researchers. "Because we have no solid biological reason to associate weight gain with the progression of triple-negative breast cancer, we now suggest that this finding be interpreted with caution."
Previous studies
Studies on the impact of weight loss on overall breast cancer risk have yielded mixed results, they noted, adding that current results were corroborated by evidence from many previous studies and analyzes.
In studies of bariatric surgery, for example, weight loss of> 20 kg was associated with a lower risk of breast cancer in severely obese women.
"Our current results suggest a benefit for less weight loss, achievable without surgery," say the authors.
The results of the current analysis are also corroborated by evidence from post-hoc analyzes of the WHI Dietary Modification test tracking data, Chlebowski said in a statement. These analyzes, conducted by the Chlebowki Research Group, were presented at the San Antonio Breast Cancer Symposium on December 15, 2014 and were reported by Medscape Medical News at this moment. They showed that after a cumulative mean follow-up of 16.1 years in more than 3,000 women diagnosed with breast cancer, a weight loss of 3% among those who followed a low-fat diet was associated with a significant improvement in overall survival after breast cancer, other cancers and cardiovascular disease compared to women who followed their usual diet.
"These findings, taken together, provide strong correlative evidence that a modest weight loss program can have an impact on breast cancer," said Chlebowski.
The conclusions of this study are not "autonomous", he said Medscape Medical News, pointing to evidence of an earlier analysis of data from the WHI observational study. This analysis, also conducted by his research team, showed that a moderate weight loss over a 3 year period resulted in a significant reduction in the risk of endometrial cancer.
However, a secondary analysis of data from the separate WHI clinical trial population, conducted by another research group, yielded somewhat different results. During a median follow-up period of 13 years, there was no association between weight loss or gain and the incidence of breast cancer in women already overweight or obese. An increased risk of breast cancer was found in women whose baseline body mass index (BMI) was less than 25.0 and who had taken more than 5% of body weight.
Asked about these differences, Chlebowski stressed that "the message is a message of moderation". Most postmenopausal women can achieve modest weight loss, he said. "Since no analysis has been observed for analyzes of obese women versus non-obese women, it is likely that even obese women could benefit as long as they avoid [weight] reduction to BMI 18.5. "
"Strong and unique proof"
Anne McTierman, MD, PhD, professor of epidemiology research at the Fred Hutchinson Cancer Research Center in Seattle, Washington, said the present study provides "solid and unique evidence that the loss weight gain after menopause is beneficial for breast cancer risk reduction. "
McTierman is also a professor of medicine at the schools of medicine and public health at the University of Washington. His own research focuses on diet, obesity, exercise, risk of cancer development and cancer prognosis.
It's never too late to reduce your risk of breast cancer.
"The bottom line here [is that] It's never too late to reduce your risk of breast cancer, "said McTierman Medscape Medical News.
Unlike previous observational studies that relied on patient-reported weight changes, the current study measured the weight of women upon arrival in the study and again three years later, she noted. In addition, the study was adjusted for other risk factors for breast cancer in a large cohort followed for more than 10 years. He also assessed the type of breast cancer in those who developed a disease, said McTierman.
"In my own clinical studies, we found that women assigned to a weight loss program with a diet alone or with a diet + exercise significantly reduced the rates of several blood factors that could promote growth. a breast tumor, compared to women assigned to a control group remained stable in weight, including estrogen, inflammation, insulin, among others, "she said.
Details of the study
For this study, investigators used data from 93,676 US women aged 50 to 79 recruited in the WHI observational study between 1993 and 1998. Their last cohort for analysis was 61,335 postmenopausal women who did not have anterior breast cancer and whose mammography results were normal.
Local laboratory reports were used to determine the status of the estrogen receptor 2, progesterone receptor, and human epidermal growth factor receptor. The BMI was calculated at baseline and at year 3. The change in weight was categorized as stable (<5%), loss (≥5%) or gain (≥5%). ). Participant self-assessments were used to determine if the weight loss was intentional.
Initially, 41% of women were of normal weight, 34% were overweight and 25% were obese.
During an average follow-up of 11.4 years, 3061 cases of breast cancer were diagnosed. Compared to 41,139 women whose weight remained stable (gain <1 lb), the analysis showed that for 8,175 women who lost weight over the three-year period, the risk of breast cancer was significantly higher. low (risk ratio). [HR]0.88; P = 0.02), without interaction by BMI. Of these, 4829 intentionally lost an average of 19.58 lbs and 3346 suffered an unintentional average weight loss of 16.90 lbs.
Women who gained 5% weight gain were more likely to be younger, black, more smoky, and younger at the time of first birth than women with stable weights. Women with intentional weight loss were more likely to have a higher BMI, but were less likely to be physically active or to be prescribed hormone therapy (P <0.01) compared to women whose weight has not changed.
The earliest weight loss was maintained until the sixth year. The average time between the beginning of the third year and the diagnosis of breast cancer was 6.47 years.
In the 12,021 postmenopausal women with an average of 18.5 lbs, the risk of breast cancer was not increased (HR, 1.02). This result was maintained after adjusting for the frequency of the mammogram. Notably, there was no significant difference in breast cancer risk, whether the weight loss was intentional or not (HR <1; P = .2 for both).
Larger studies are needed to provide a more definitive understanding of the role of intentional weight loss versus unintentional weight loss in cancer risk, say the authors.
McTierman noted that there is strong evidence that women can reduce their risk of breast cancer in postmenopausal women by maintaining a BMI of less than 25, staying physically active, eating healthily, not smoking, by drinking little or no alcohol and by submitting regularly to a recommended mammographic screening.
For patients requiring hormone therapy to manage the symptoms of menopause, she insisted that progesterone should be avoided or that its use should be limited to less than 3 years. She also said that so-called bio-identical hormones and hormonal creams and gels are "no safer than prescription hormones and should be avoided".
Evidence that the use of hormones for the treatment of postmenopausal symptoms may increase the risk of breast cancer comes from previous analyzes of two separate randomized trials of WHI, also conducted by Chlebowski. These showed that the combined use of estrogens and progestogens for an average of 5.6 years significantly increased the risk of breast cancer (HR, 1.3) and that this high risk persisted. after 13 years of follow-up.
McTierman stated that for women with a strong family history of breast cancer, a BRCA a gene mutation, or cancer precursor, additional MRI or ultrasound screening can add valuable information to the results of regular mammography screening for the early detection of breast cancer. Clinicians can also discuss the pros and cons of estrogen blocking drugs such as tamoxifen (multiple brands), raloxifene (Evista, Eli Lily) and aromatase inhibitors, she suggested.
Mastectomy and / or prophylactic oophorectomy significantly reduces the risk of breast cancer, noted McTierman. "Clearly, these options are the most appropriate for women at very high risk," she said.
In high-risk women who undergo bilateral mastectomy, the risk of breast cancer is reduced by more than 90%, she said. In women undergoing bilateral oophorectomy, the risk of breast cancer is reduced by about half compared to high-risk women whose ovaries are intact.
The WHI observational study was funded by the National Institute of Heart, Lung and Blood, the National Institutes of Health and the Department of Health and Social Services. The analysis was supported by the American Institute for Cancer Research. Dr. Chlebowski maintains financial relationships with AstraZeneca, Novartis and Pfizer. No other significant financial relationship has been reported.
Cancer. Posted online 8th October 2018. Summary
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