"The OncotypeDx result is reported as a single score but it is made up of 16 informative genes and five control or "housekeeper" genes that we have studied in detail. Some of the 16 are considered as groups rather than individual genes, and one of these is the E-module, which consists of four genes that are related to oestrogen signalling, including the oestrogen receptor itself," he explained.
OncotypeDX has been used for over 350,000 tests and the ATAC team had previously shown that its prediction of recurrence was poorer in the second five years after a patient's diagnosis than in the first five years. The researchers wanted to find out the reason for this, and to do so they determined the relationship between the expression of the individual genes and gene modules and early (up to five years) and late (between five and ten years) recurrence rates in women with ER+ HER2- breast cancer.
They assessed the gene expression and recurrence rates in 1125 women in the ATAC trial, who had an average of ten years of follow-up. Nearly 90% of the women were HER2- and there were 215 recurrences during the ten years.
They found that recurrence rates were highest in the first five years for women with HER2+ breast cancer, compared with the subsequent five years, but for women with HER2- cancer, the recurrence rates were higher between five and ten years.
"When we looked at the women with HER2- breast cancer and defined them according to their E-module score, which indicated how sensitive to oestrogen their tumours were, we found that there was a striking difference," said Prof Dowsett. "Among women with tumours most sensitive to oestrogen, with a high E-module score, the recurrence rate more than doubled from 5.7% in the first five years to 13.6% in the subsequent five years. However, if they had a low E-module score, there was little difference in recurrence rates between the first five years and
|Contact: Emma Mason|
ECCO-the European CanCer Organisation