Nearly 40% of breast cancer tumours change form when they spread, recent research suggests.

Breast cancer 'changes' as it spreads

More than 45,500 women are diagnosed with breast cancer in the UK every year
Research has found that “nearly 40% of breast cancer tumours change form when they spread,” BBC News reported. It said that the finding could mean cancer patients may need changes to their treatment regime.
This research found that some tumours changed the type of proteins they produced when they spread from the breast to the lymph nodes (the area of the body where breast cancer often spreads first). As tumours are more likely to respond to certain treatments depending on which proteins they produce, such changes may have an impact on the effectiveness of some treatments.
However, the study contained relatively few cancer patients with certain types of tumour and it could not assess the effect of the changes on treatment. As such, the results will need to be verified by further research involving more patients and which examines whether the outcome of treatment is affected.
It is too early to know whether reassessing the characteristics of breast cancer tumours that have spread to the lymph nodes would help choose more effective treatment.

The research was carried out by Dr S J Aitken and colleagues from the Breakthrough Research Unit at the University of Edinburgh. It was funded by Breakthrough Breast Cancer, the Scottish Funding Council and Cancer Research UK. The study was published in the peer-reviewed medical journal Annals of Oncology.
In general, the BBC gave a balanced report of this research. It notes that “a clinical trial needs to be carried out to fully evaluate the benefits of testing cancer cells in the lymph nodes before it can be approved for use on the NHS."

This study reports that the characteristics of breast tumours may change as they spread through the body. It gives further insight into the behaviour of cancer cells, but its findings will require confirmation in other studies.  Other points of note are:
Although the study included samples from a relatively large number of women, comparatively few had certain characteristics (for example, those who tested negative for all three proteins). As such, the findings will need to be confirmed by other studies.
The study only looked at lymph node metastases (spread). It cannot show what happens when the cancerous cells spread further throughout the body.
Although the findings provide a possible reason why cancer treatments may fail, as the researchers report, their study was too small to look at whether these changes predict treatment failure. Further studies will be needed to assess whether this is the case.

Aitken SJ, Thomas JS, Langdon SP, Harrison DJ and Faratian D. Quantitative analysis of changes in ER, PR and HER2 expression in primary breast cancer and paired nodal metastases. Annals of Oncology 2009, first published online on October 25 2009