Weight Loss Blog

Breast cancer patients who are overweight have more aggressive disease and are likely to die sooner, U.S. researchers reported on Friday.

A dangerous type of breast cancer, known as inflammatory breast cancer, was seen in 45 percent of obese patients, compared with 30 percent of overweight patients and 15 percent of patients of healthy weight.

“The more obese a patient is, the more aggressive the disease,” said Dr. Massimo Cristofanilli of the University of Texas M.D. Anderson Cancer Center, who led the study.

“We are learning that the fat tissue may increase inflammation that leads to more aggressive disease.”

Writing in the journal Clinical Cancer Research, Cristofanilli and colleagues said they studied 606 women with breast cancer that had spread within the breast.

They classified them according to body mass index or BMI, a globally accepted measure of obesity. People with BMIs of below 25 are considered normal, while 25-29 marks overweight and 30 or above is clinically obese.

After five years, 56.8 percent of obese women and 56.3 percent of overweight women were still alive. But 67.4 percent of the normal weight women had survived.

More than 56 percent of women of normal weight survived 10 years, compared to 42.7 percent of obese women and 41.8 percent of overweight women.

“Obesity goes far beyond just how a person looks or any physical strain from carrying around extra weight. Particular attention should be paid to our overweight patients,” Cristofanilli said.

Many studies have shown that the obese have a greater risk of several types of cancer. Last month British researchers reported in the Lancet medical journal that obesity can double the risk of leukemia, multiple myeloma, thyroid cancer, colon and kidney cancers.

Fat cells produce a range of hormones that could fuel cancer, researchers say.

Locally advanced breast cancer more deadly in obese

Women with locally advanced breast cancer who are overweight have a worst prognosis than their slimmer counterparts, US researchers reported.

An aggressive type of breast cancer, known as inflammatory breast cancer, was also seen in significantly more obese and overweight patients than in normal-weight patients, according to the study, published in the journal Clinical Cancer Research.

“The more obese a patient is, the more aggressive the disease,” said principal investigator Dr. Massimo Cristofanilli of the University of Texas M.D. Anderson Cancer Center in Houston. “We are learning that the fat tissue may increase inflammation that leads to more aggressive disease.”

Cristofanilli and colleagues studied 602 women with locally advanced breast cancer. They classified the patients by body mass index (BMI), the ratio of height to weight, frequently used to measure obesity. (People with BMIs of less than 18.5 are underweight; between 18.5 and 24.9 is considered normal; 25.0 to 29.9 is overweight; and 30 or higher is obese.)

After fiveyears, the researchers report that 58.6 per cent of the obese women, 58.3 per cent of the overweight women and 69.3 per cent of the normal-weight women were still alive.

After ten years, 57.3 per cent of normal- or underweight had survived compared with 42.4 per cent of obese women and 44.1 per cent of overweight women.

“Obesity goes far beyond just how a person looks or any physical strain from carrying around extra weight. Particular attention should be paid to our overweight patients,” Cristofanilli said.

Many studies have shown that the obese have a greater risk of several types of cancer. Last month British researchers reported in The Lancet medical journal that obesity can double the risk of leukemia, multiple myeloma, thyroid cancer, colon and kidney cancers.

Breast cancer, blood sugar and body fat

“Big C risk is worse if you’re fat” reads the headline in The Sun today. The news story it refers to goes on to say that fat women are “less likely to get low-risk breast cancer – but more prone to life-threatening versions”. The researchers have “discovered a link between the fiercest types [of breast cancer] and high blood sugar”, the newspaper adds.

The newspaper report is based on a Swedish study investigating metabolic factors and breast cancer risk. There were few results of statistical significance this study so it is impossible to reach firm conclusions. Although this study adds evidence to previous research which suggests a complex link between metabolism and breast cancer, more studies are needed to identify what this risk is. This study is not conclusive and The Sun and other news sources have overstated its significance.

Where did the story come from?
Dr Anne Cust, Tanja Stocks and colleagues from the University of Melbourne, the University of Sydney, the International Agency for Research on Cancer (France), Umea University in Sweden and the German Cancer Research Centre carried out this research. The study was funded by the World Cancer Research Fund, the Swedish Cancer Society and the council of Vasterbotten county in Sweden. It was published in Breast Cancer Research and Treatment, a peer-reviewed medical journal.

What kind of scientific study was this?
The study was a nested case-control study designed to explore the relationship between body mass index (BMI), the hormones involved in metabolism (leptin and adiponectin), some of those involved in controlling blood-sugar levels (C-peptide and glycated haemoglobin) and breast cancer risk among women in northern Sweden.

The researchers had access to data from several different groups of women who were involved in the Northern Sweden Health and Disease Cohort (NSHDC). One part of the NSHDC ran from 1985 to 1996 and another part has taken place since 1995. In September 2005, they linked all women for whom they had blood samples to the regional cancer register (which records 99% of breast cancer diagnoses). Of these women, 561 had a diagnosis of breast cancer. From the same population (i.e. women who came from the original groups and had blood sample records available), they selected one control for each case. The case-control pairs were matched on age at baseline and the date when their blood samples were taken.

The researchers looked at the blood samples from the women who had breast cancer and compared them with those who did not. They were particularly interested in whether the levels of particular hormones that regulate metabolism (leptin and adiponectin) were different between the groups. They also compared the levels of chemicals involved in regulating blood sugar: C-peptide and glycated haemoglobin.

What were the results of the study?
Overall, the researchers found that BMI, leptin, adiponectin, C-peptide and glycated haemoglobin had no effect on the levels of risk of any type of breast cancer (stages I–IV). When the researchers divided the women into two groups (those with stage I tumours and those with stage II–IV tumours), they found a slightly different pattern of results: obese women were much less likely than normal weight women to have stage one breast cancer.

Women with higher levels of glycated haemoglobin were also less likely to have stage I breast cancer than those with lower levels. The researchers acknowledge that the mechanisms underlying this decreased risk are unclear.

For breast cancer stages II-IV, there were no statistically significant patterns. That is, although a greater number of obese women had stage II-IV breast cancer than normal weight women, this was not statistically significant.

In overweight or obese women, higher levels of glycated haemoglobin had a borderline significant association with risk of more severe tumours.

What interpretations did the researchers draw from these results?
The researchers conclude that their study has found an inexplicable reduction in risk of stage I breast cancer among obese women compared with normal weight women. They also found a reduced risk of stage one breast cancer among women with high “blood sugar” compared with those with normal blood sugar. Furthermore, the study found that higher levels of leptin and glycated haemoglobin together with higher BMI had “a suggestion of an increased risk” of stage II–IV breast cancer.

What does the NHS Knowledge Service make of this study?
In isolation, the lack of statistical significance in the results linking BMI and other markers of metabolism with risk of more severe breast cancer mean that this study is not conclusive. The claim in The Sun that “high blood sugar in overweight women hugely increases the risk of aggressive tumours” is an overstatement of these results. The authors discuss other evidence that links a particular metabolic profile (overweight, insulin resistance) to progression of tumours. However, they are cautious about their conclusions from this study, saying that there is only a “suggestion of an increased risk”.
Other limitations that the authors raise include the study’s reliance on the results from only one blood sample, which is unlikely to represent metabolism over the long term. They were also unable to explore in detail the contribution of age differences between the women to the differences in risk.

This research is inconclusive, though it may add some evidence to other research into the relationship between metabolism and breast cancer. Until further studies replicate these findings with statistical significance, this relationship will remain unclear.

High blood sugar and body fat increase breast cancer risk

WOMEN who are overweight or have high blood sugar could be more at risk of developing aggressive breast cancer, research shows.
A new study is believed to be the first to look at how excess body fat and blood sugar levels affect the chance of developing different types of tumours.

It found women were less likely to suffer low-risk breast cancer if they were overweight or suffered high blood sugar (insulin resistance), but were at higher risk of more aggressive tumours.

Experts at Umea University in Sweden carried out the study, funded by the World Cancer
Research Fund, and
published in the journal Breast Cancer Research and Treatment.

They looked at blood samples and measurements including body mass index (BMI) taken from more than 1,000 women. Of the group, 561 women had been diagnosed with breast cancer while 561 remained free of the disease and acted as a control.

The study found that the association of BMI, leptin (a hormone linked to body fat) and HbA1c (a blood sugar reading) and breast cancer risk differed significantly according to whether the tumour was diagnosed as early stage I or more advanced stages II to IV.

Dr Sarah Cant, policy manager at Breakthrough Breast Cancer, said: “We already know that being obese after the menopause increases the risk of developing breast cancer but this research is the first to suggest being overweight and having high blood sugar levels may affect the stage of breast cancer at diagnosis.”