The researchers say that their results show that, despite similar overall recurrence rates for patients with ER+ tumours between the first five years and the next five to ten years, there were important differences between groups of tumours with different genetic expression profiles.
"Importantly, HER2- tumours that are very sensitive to oestrogen are usually considered to be relatively low risk, yet these were the tumours that showed an increase in recurrence after five years, which coincided with the cessation of adjuvant hormonal therapy," said Prof Dowsett. "It is commonly thought that the reduction in recurrence achieved by five years of endocrine therapy 'carries-over' into the next five years. Our results suggest this effect may differ markedly between different groups of ER+ tumours. We need to do more detailed analyses on large numbers of tumours to find out if this is the case."
He said the results also suggested a way in which methods of predicting recurrence using genetic signatures may be improved. "Better predictors of recurrence than the OncotypeDX and others currently being used should be possible based on the different recurrence rates of different groups of tumours and their different sensitivity to endocrine therapy." He and his colleagues are already working to see if they achieve this.
"We are already testing over 900 tumours from the ATAC trial to see if we can identify the oestrogen-sensitive tumours better than by the genes in the Oncotype test. This will allow us to see whether, using the knowledge from this work, we can indeed create better predictors of recurrence both for the first five years and subsequent years after diagnosis," he said.
The findings could change clinical practice: women with HER2-, high oestrogen signalling breast cancer might be considered for adjuvant hormone therapy that is extended to ten years. However, the results need to b
|Contact: Emma Mason|
ECCO-the European CanCer Organisation