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Why does breast cancer often spread in obese women?

Every year, approx. 5,000 Danish women are diagnosed with breast cancer. Obesity makes the cancer cells more aggressive, so they spread to other parts of the body. This is the focus of Rasmus Siersbæk’s research and he hopes to be able to find better treatment methods for this disease.

By Birgitte Svennevig, , 1/14/2021

The primary tumour is not the most common cause of death for breast cancer patients. Instead spreading of cancer cells to other parts of the body is the leading cause of death, and it is currently not possible to control this process.

– Several large studies have shown that obese people are at greater risk of two things when it comes to breast cancer: Firstly, there is a greater risk of getting cancer. Secondly, there is a greater risk that the cancer will spread, says Rasmus Siersbæk.

He has done research in breast cancer for more than five years and is currently assistant professor at the Department of Biochemistry and Molecular Biology, University of Southern Denmark.

How is the spread related to obesity?

Not many people are aware of the connection between cancer and obesity, and according to Rasmus Siersbæk, it is important to spread the word.

– It is not a matter of making obese people feel guilty, but we should all have proper information about factors that can have a great impact on our health, he says.

The human organism is an extremely complex universe in which cells interact with each other in many different ways, and it is such interactions between the normal cells of the body and the cancer cells that can change in obese patients.

Healthy cells ‘talk’ to cancer cells

– The normal cells in the body ‘talk’ to the cancer cells using small signalling molecules. If you are obese, the fat cells and immune cells, for example, change so that the signals they send increase the ability of the cancer cells to spread to other parts of the body.

– We are interested in decoding these signals, so we can stop them and thereby inhibit the spread of the cancer cells, says Rasmus Siersbæk.

Breast cancer

  • Breast cancer is one of the most common cancers in Denmark
  • The risk of dying from the disease has been declining for the past 20 years
  • Since 2000, the 5-year survival rate has increased from 78% to 87%.

The ultimate goal is to be able to offer cancer patients a treatment that, in addition to inhibiting the growth of the tumour, also inhibits the spread of cancer cells to the rest of the body.

Rasmus Siersbæk has previously spent four years in Cambridge in England studying such a signalling pathway from healthy cells to cancer cells, which affects the spread of cancer cells.

Based on this research, and with the support from the Novo Nordisk Foundation and the Danish Cancer Society, he continues his research at the University of Southern Denmark, where he studies the mechanisms that control the growth and spread of cancer cells in the body and the effect of obesity on this process.

Photo: Mikkel Linnemann Johansson

Meet the researcher

Rasmus Siersbæk is a PhD and assistant professor at the Department of Biochemistry and Molecular Biology. He does research in breast cancer.


Editing was completed: 14.01.2021