The TAILORx prospective study provides the best evidence yet that a 21 gene assay can identify women with breast cancer who can be sparred chemotherapy, reports the New England Journal of Medicine.

Previous studies have shown the 21-gene expression assay, produced by Oncotype DX, can provide additional prognostic information independent of clinicopathologic features and predict benefit from adjuvant chemotherapy in oestrogen-receptor-positive disease.

Since validation in prospectively conducted studies provides the highest level of evidence supporting clinical validity, Joseph Sparano and colleagues, from Montefiore Medical Center, New York, undertook the Trial Assigning Individualised Options for Treatment (TAILORx) study.

Between April 2006 and October 2010, 10,253 women aged 18 to 75 years with axillary node–negative invasive breast cancer (that was oestrogen-receptor–positive or progesterone-receptor–positive, or both, and that did not overexpress HER2) had a reverse-transcriptase–polymerase-chain-reaction 21-gene assay performed on RNA extracted from formalin-fixed paraffin-embedded tissue.

The study was undertaken in a central laboratory (Genomic Health).

Results showed 1626 women had a recurrence score of 0 to 10 (indicating low risk); 6907 had a score of 11 to 25 (indicating midrange risk); and 1736 had a score of 26 or higher (indicating high risk).

In the low risk cohort of patients (with a recurrence score of 0 to 10) the rate of invasive disease–free survival at five years was 93.8% (95% CI, 92.4 to 94.9); the rate of freedom from recurrence of breast cancer at a distant site at five years was 99.3% (95% CI, 98.7 to 99.6); the rate of freedom from recurrence at five years was 98.7% (95% CI, 97.9 to 99.2); and the rate of overall survival at five years was 98.0% (95% CI, 97.1 to 98.6).

"This prospective study involving uniformly treated patients with hormone-receptor positive, HER2-negative, axillary node-negative breast cancer supports the clinical validity of the 21-gene assay in identifying patients who may be safely spared adjuvant chemotherapy," write the authors.

In an accompanying commentary Clifford Hudis from Memorial Sloan Kettering Cancer Center, New York, writes, “ For now, however, this assay is the most rigorously tested option and provides proof of the principle that we can develop reproducible predictive tests to select patients who should not receive chemotherapy. In that regard, it is one more step toward precision. There are more steps ahead.”

Source: The New England Journal of Medicine

Reference:

J Sparano, R Gray, D Makower, et al. Prospective Validation of a 21-Gene Expression Assay in Breast Cancer. NEJM September 28, 2015. 

C Hudis. Biology before Anatomy in Early Breast Cancer – Precisely the Point. Ibid, September 28, 2015.