Overweight, Obese Women at Greater Risk of Breast Cancer Recurrence, Death
Problem persists even after adjusting chemo dose for weight; no proof that losing weight after diagnosis will make a
2012 -Women who are overweight or obese when they are diagnosed with breast cancer are at higher risk of cancer
recurrence or related death than are leaner women, according to a new study to be presented to the 8th European Breast Cancer Conference
(EBCC-8) today by U.S. researchers.
This finding held true even though the study mandated that chemotherapy dosage be adjusted for body weight, and adds to
the evidence that lifestyle factors can influence cancer prognosis, Dr. Jennifer Ligibel, a medical oncologist at the Dana-Farber Cancer
Institute, Boston, and an Associate Professor at Harvard Medical School will tell the conference.
Dr. Ligibel and colleagues studied data from 1909 patients who were enrolled into a study called CALGB 9741 between 1997
and 1999. The study was set up to investigate different dosing schedules for adjuvant chemotherapy in patients where cancer cells were found
in the lymph nodes (node-positive cancer).
The presence of such cells in the lymph nodes means that there is a higher chance of cancer returning after surgery.
After extracting height and weight data from the patient records, they went on to evaluate the relationship between body
mass index (BMI) with relapse-free survival (RFS) and overall survival (OS).
The breakdown of women in the study by weight were -
● 1.2% of the patients were underweight,
● 32.6% normal weight,
● 32.9% overweight and
● 33.3% obese.
Additionally, 49% of patients were menopausal, 65% had estrogen-receptor positive cancers, where the presence of estrogen
encourages the tumor to grow, and 70% received the estrogen-receptor blocking treatment, tamoxifen.
"Several other studies have shown that being overweight or obese at the time that a woman is diagnosed with breast cancer
is linked to a higher risk of recurrence. However, questions have been raised in the past whether obese women were receiving relatively lower
doses of chemotherapy due to their weight," said Ligibel.
"Our study mandated that each patient received a chemotherapy dose adjusted to her weight, so these results suggest that
treatment factors are not responsible for the differences in recurrence rates seen in heavier women.
"We found that BMI was related to both RFS and OS; for example, the ten-year RFS of a patient who was overweight was 70%;
compared with 65% for one who was obese."
Although the link between obesity and the development of breast cancer is well known, there has been less research to
date looking at its effect on cancer recurrence and survival.
"When you consider that data from 2007-8  show that 68% of US adults aged 20 years and over were overweight or obese,
as compared to only 56% of the same group in 1998-1994, you can see the way the problem is growing. That is why we think it is a matter of
urgency to find out as much about the relationship between obesity and cancer as we can," Dr. Ligibel will say.
Ligibel was referring to the 2007-8 data from the US National Health and Nutrition Examination Survey (NHANES).
The researchers intend to follow up their work by learning more about how weight-related factors could influence breast
cancer outcomes. A number of studies currently underway are looking at how changing lifestyle behaviors, for example losing weight, exercising
more, and eating a better diet, affects the hormones in women's bodies that have been linked with breast cancer.
Ultimately, they say, they are interested in studying the impact of deliberate weight loss on the risk of recurrence in
women with early breast cancer.
"Obesity is a modifiable factor, and although there is not yet enough evidence to say with certainty that losing weight
or exercising more regularly will decrease the risk of breast cancer recurrence, there are consistent links between lifestyle factors such as
diet, weight and physical activity patterns and breast cancer prognosis. If future studies show that making changes in lifestyle behaviors for
women with early breast cancer will improve survival rates, then lifestyle interventions may one day become a standard part of breast cancer
care," Dr. Ligibel will conclude.
Professor David Cameron, from the University of Edinburgh (U.K.) and chair of EBCC-8 said: "Whilst these are important
findings for women with breast cancer, we need to recognize that the reason overweight women have poorer outcomes is not clear. There are a
lot of health reasons why overweight women should try and get back to a normal weight, but this is not always easy, and as the authors
acknowledge, we don't yet know that losing weight after a breast cancer diagnosis will make a difference."
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