Scientists at the Cancer Research UK Cambridge Institute have discovered more about the way breast cancer spreads.

Breast cancer cells. Picture: LRI EM Unit (13198655)

The researchers believe advanced breast cancer probably spreads in waves, rather than continuously - a finding that could help to change the way patients are treated.

They studied 181 tumours collected during post mortem examinations on 10 women who had died from breast cancer that failed to respond to treatment and spread to other parts of the body.

Comparing the molecular make-up of the tumours, they uncovered clues on how the cancer evades the immune system, spread and become resistant to treatment.

They collected up to 37 tumours from the same patient, and found several were genetically very similar, as if they started from the same source.

Each patient’s tumours could be grouped, they found, in a just a few ‘family trees’.

The team believes this pattern results from a group of cancer cells creating new tumours in several organs at the same time.

Breast cancer cells. Picture: LRI EM Unit (13198653)

This could be cells breaking away from the primary tumour or from elsewhere in the body, where cancer cells can remain hidden and dormant, sometimes for years.

The number of ‘spreading events’ experienced by the patients ranged from one to three.

Professor Carlos Caldas, from the University of Cambridge Cancer Research UK Cambridge Institute, said: “We were lucky to have a rare and first in-depth look at these advanced cancers, and then we realised that what we thought we knew might be wrong.

“Breast cancer doesn’t appear to spread continuously with the initial tumour shedding cells one by one, but it spreads in waves.”

Prof Carlos Caldas at the Cancer Research UK Cambridge Institute. (13198728)

Prof Caldas is a national co-ordinator for breast cancer in the PEACE trial, a partnership between Cancer Research UK and UCL that enrols patients across the UK who agree to have samples of their cancer taken after their death for analysis.

David Scott, director of discovery research at Cancer Research UK, said: “This is the largest study of its kind to date and gives an unprecedented view of the behaviour of advanced cancers.

“Studying advanced cancer in this much detail is only possible thanks to the precious gift from patients who have donated their bodies so they may help others.

“Cancer Research UK is proud to honour their legacy, which will support many other studies, such as the PEACE trial.”

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