The study reviewed here found that overweight or obese Danish women diagnosed with breast cancer had a worse prognosis than women at a healthy weight. These results were reported at the 2009 San Antonio Breast Cancer Symposium.
Women who were obese at the time of diagnosis were more likely to:
Women who were overweight but not obese at the time of diagnosis had similar increases in risk.
Women at a healthy weight were more likely to benefit from chemotherapy and hormonal therapy medicines given to reduce the risk of the cancer coming back.
This very large study was done in Denmark and looked at the weight and medical records of 19,000 women diagnosed with breast cancer between 1977 and 2006. A woman's weight was classified by body mass index (BMI). BMI uses your weight and height to determine if you're underweight, normal weight, overweight, or obese.
Compared to normal weight women, women who were overweight or obese were diagnosed with cancers that:
Compared to normal weight women, obese women had an 11% greater risk of dying from breast cancer during the 10 years after diagnosis. The risk of dying from breast cancer more than 10 years after diagnosis was also greater for obese and overweight women. Compared to normal weight women:
Overweight and obese women didn't respond as well to treatment compared to normal weight women. Normal weight women had the best response to adjuvant chemotherapy and hormonal therapy (treatments given after surgery to reduce the risk of the cancer coming back). Normal weight women were 77% more likely to benefit from chemotherapy and 57% more likely to benefit from hormonal therapy compared to women who were obese, after 10 years of follow-up.
This study strongly suggests that being overweight or obese makes breast cancer prognosis worse. Excess weight is associated with more aggressive cancers and a decrease in treatment benefits. Researchers don't completely understand why extra weight is associated with these effects. One possible reason is the effect body fat has on the hormone estrogen. Extra body fat can increase estrogen levels and estrogen can make breast cancers grow.
Many women are frustrated and unhappy because they gain weight during and after breast cancer treatment. This is especially true for women who get chemotherapy and/or hormonal therapy. Chemotherapy can cause early menopause, which makes it much easier to gain weight. But there are other reasons women gain weight after diagnosis:
If you've been diagnosed with breast cancer, try to make exercise and a healthy diet part of your daily routine, especially if you are overweight or obese. It may be hard to make these kind of changes if you're struggling to recover from treatment. Some women say it helps to think of eating well and exercising as important parts of their treatment plan. You might want to talk to your doctor or a registered dietitian to develop a healthy eating plan designed specifically for you and your needs. Losing weight is hard to do. But it can be done with exercise and careful diet changes. Be nice to yourself; don't punish yourself. Always tell your doctor about any new diet or exercise plans you're using.
In the Breastcancer.org Nutrition section, the Eating to Lose Weight After Treatment pages can help you asses your weight and create a healthy eating and exercise plan to reach and maintain a healthy weight.
SAN ANTONIO (MedPage Today) -- Obesity significantly worsens breast cancer prognosis, including response to therapy and survival, data from a large Danish study showed.
Compared to normal-weight breast cancer patients, obese patients had as much as a 38% greater risk of breast cancer mortality 10 years after diagnosis. Obesity increased the risk of distant metastasis by almost 50%.
Normal-weight women also were as much as 77% more likely to benefit from adjuvant systemic therapy for breast cancer.
"The poorer prognosis among obese patients with breast cancer is likely due to diagnosis at a more advanced stage and a higher risk of developing distant metastases," Marianne Ewertz, MD, of Odense University Hospital, said at the San Antonio Breast Cancer Symposium.
"Additionally, adjuvant treatment seems to lose its effect more rapidly in obese patients," she added.
Studies have shown that obesity increases the risk of dying from breast cancer. However, the reasons for the increased mortality hazard have remained unclear. One possible explanation is that obesity reduces the efficacy of breast cancer therapy.
To examine obesity within the context of adjuvant breast cancer therapy, Ewertz and colleagues reviewed data on 53,816 Danish women treated for breast cancer from 1977 through 2006. The data included detailed information about demographic, clinical, and pathologic characteristics of each woman's cancer.
Investigators calculated body mass index (BMI) for 19,000 of the women, and used BMI as a surrogate for obesity. They defined a normal BMI as <25 and found that women with a higher BMI were usually older and more often postmenopausal. Here are some of the findings:
An analysis of survival by type of adjuvant therapy showed that women with a BMI <25 derived greater benefit from chemotherapy up to 10 years after diagnosis and more than 10 years after diagnosis.
The effect of BMI on hormonal therapy was less consistent.
Differences in therapeutic benefit were greatest for women with a BMI <25 who had been followed for more than 10 years. They were 77% more likely to benefit from chemotherapy and 57% more likely to benefit from hormonal therapy, compared with women who had a BMI >30 and were followed for 10 years.
Future studies should focus on identifying reasons for the differences in the effects of adjuvant therapy, Ewertz said.
The results underscore the importance of maintaining body weight within a normal range. Additionally, women with an above-normal BMI should be targeted for regular screening mammography, she said.
Ewertz disclosed relationships with GlaxoSmithKline and Novartis.
Primary source: San Antonio Breast Cancer Symposium Source reference: Ewertz M, et al "Effect of obesity on prognosis after early breast cancer" SABCS 2009; Abstract 18.
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