Three scientists have set out to find more effective treatment for a growing proportion of women who are obese and have breast cancer.
Obesity is not only a risk factor for developing breast cancer, but also determines how effective treatment is, researcher Dr Margaret Currie said.
Currie has teamed up with Associate Professor Gabi Dachs and Dr Logan Walker from the Mackenzie Cancer Research Group for the project, which is funded by the Cancer Society and the New Zealand Breast Cancer Foundation.
The University of Otago, Christchurch, group's initial studies showed that when obese fat cells were cultured together with breast cancer cells, the breast cancer cells became more resistant to chemotherapy drugs.
"They are still able to proliferate and have metabolic activity, even though they should be dying due to the chemo."
Cancer cells also became more migratory, spreading to other parts of the body.
"When you become obese the fat cells become obese too, they are absolutely stuffed with lipids and it changes the way they act," Currie said.
The findings had huge implications for treatment, she said.
"We think this is quite a small but dangerous population of breast cancer cells that we need to find new drugs to target."
The next stage would involve testing different medications, which might target the cancer cells in obese women more effectively.
Metformin - a drug widely used to treat Type 2 diabetes - has been tested already with promising findings.
"Obesity has been linked to an increased risk of getting breast cancer if you are post menopausal, but what we are interested in is no matter what age you are, once you have breast cancer, if you're obese, you are likely to do worse," Currie said.
"What we are working towards is improving chemotherapy outcome for these patients".
Breast cancer cost New Zealand about $127 million every year, with each diagnosed case costing about $45,000, University of Otago, Wellington, public health researcher Dr Nick Wilson said.
Well established evidence showed a clear link between obesity and breast cancer, and the most cost-effective response by the Government would be to regulate the food industry through taxation and labelling, he said.
"The Government, I think, is shooting itself in the foot by not starting to regulate soft drink because it's just leaving the taxpayer to foot the bill downstream with increased diabetes and obesity related cancers and heart disease."
Breast cancer and obesity: the facts
- Breast cancer patients who are obese before or after diagnosis are less likely to survive than patients with normal BMI.
- The risk of dying from breast cancer increases by a third for every increase of 5kg/m2 in BMI.
- About 30 per cent of New Zealanders are overweight and another 40 per cent are obese.
- Death from breast cancer in Māori is double that of non-Māori.
- Breast cancer is the most commonly diagnosed cancer in New Zealand women, and the second-most common cause of cancer death.