How being obese could help you FIGHT cancer

July 6, 2015  12:58

Overweight cancer patients are more likely to survive after treatment for advanced stages of the disease, new research has revealed.

Doctors branded their findings a 'surprise', having expected thinner patients to fare better.

Their study found patients with a low to healthy body mass index (BMI) lived on average two-and-a-half months less than overweight and obese patients.

The results shocked researchers, who had predicted obese patients would not react as well to treatments for stage 4 colorectal cancer because of their increased risk of developing the disease and it returning.

Past research has also shown many obese cancer patients receive less-than-optimal dosages of cancer drugs, or have other health problems that complicate their recovery.

Lead author of the new study, Dr Yousuf Zafar, of Duke University in North Carolina, said: 'Contrary to our hypothesis, patients who had the lowest BMI were at risk for having the shortest survival.

'In this case, patients with the lowest body weight - people who had metastatic colon cancer [that which had spread] and a BMI of less than 25 - were at the highest risk.' 

According to guidelines, a healthy adult's BMI ranges from 18.5 to 24, while a BMI below 18.5 is deemed underweight. 

Researchers examined data from 6,128 patients who had previously been untreated for their metastatic colorectal cancer, from four different studies in the US and Europe.

Their average BMI at the start of cancer treatment was 25.3, considered slightly overweight. 

All received the drug bevacizumab with chemotherapy as part of their treatment.

Bevacizumab, also known by the brand name Avastin, is used in patients with metastatic cancer to slow the growth of new blood vessels. 

Researchers divided patients into four BMI ranges, and measured participants' survival rates.

They also measured the length of time that patients' tumours stopped growing, which was measured as progression-free survival.

Patients with the lowest BMI from 20 to 24.9, which would be considered a healthy weight according to BMI guidelines, survived an average of 21.1 months after starting their treatment.

Those with a BMI of 25 to 29, considered overweight, survived two-and-a-half months longer, researchers found.

Furthermore, obese patients seemed to fare best. 

Patients deemed obese with a BMI of 30 to 35, survived an average of 24 months.

And those with BMIs of 35.1 and higher, survived an average of 23.7 months.

Although the study found significant differences in how long a patient lived based on their BMI ranges, patients of all weights saw similar rates of progression-free survival, or a halt in their tumour growth. 

Patients whose tumours stopped growing went an average of 10 months without progression, but the stoppage in tumour growth does not necessarily improve chances of survival.

The study does not indicate that being overweight is in any way protective for patients undergoing cancer treatment, Dr Zafar said. 

Instead, the results suggest that there could be an aspect of biology that could put thinner patients at a higher risk for poor outcomes, he said.

Dr Zafar said: 'There may be a relationship between having a lower BMI and how much treatment patients can tolerate.

'I would hypothesise that the lowest weight patients in our analysis received or tolerated less treatment, or received adequate treatment at first, but became too sick to receive additional therapy.

'That may be where we can focus more attention on improving their outcomes.'

The study was presented at the European Society for Medical Oncology World Congress on Gastrointestinal Cancer. 

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