Data presented at the International Breast Cancer Conference at St Gallen, Switzerland has shown that gene expression testing for early-stage breast cancer is working well in getting patients onto more appropriate treatment in Europe.

The Oncotype DX breast cancer test, developed by Genomic Health, provides a snapshot of tumour activity at the molecular level by measuring the expression of 21 genes (composed of 16 breast cancer genes and five reference genes). Readouts are fed into mathematical equations, giving a numerical figure to the likelihood of benefitting from chemotherapy and experiencing a metastasis over the next ten years on scales between 0 and 100.

"In the past, we've used a one-size-fits-all approach where all women with early-stage breast cancer get offered chemotherapy," said Steven Shak,  chief medical officer at Genomic Health. "But in reality only four out of 100 women actually benefit, with the remainder experiencing unnecessary toxicity."

The Oncotype DX test is widely used in the USA where it was launched in 2004 and is now routinely offered to women with stage I or II node negative and oestrogen receptor positive disease. What has been less clear is whether the test would be valuable in UK health care settings that traditionally use less chemotherapy. Simon Holt, a surgical oncologist at the Prince Philip Hospital (Llanelli, Wales) presented a prospective analysis of 107 patients who had undergone testing with the South West Wales Breast Cancer Network. In the study he analysed how many women initially evaluated with the Nottingham Prognostic Index (the current evaluation tool) had treatment decisions changed following evaluation with the Oncotype DX technology.

Results showed that overall, 33% of patients in the study had their treatment decisions changed. This was composed of 23.6% who changed from receiving both chemotherapy and hormone therapy to just receiving hormone therapy and 9.4% who switched from just receiving hormone therapy to receiving hormone therapy plus chemotherapy. "From the clinical perspective, it's probably more important to identify those patients who'll benefit from chemotherapy," said Holt, adding patients were quite happy to undergo treatment once they appreciated its significance.

Genomic Health already has an assay in colon cancer, launched in 2010, and another in development in prostate. "Future assays may even be able to show whether anthracyclines or taxanes would be more effective in individual patients," said Shak.