LONDON, July 17 — The genomic test that changed how oncologists decide whether to give chemotherapy for early breast cancer now has company. Oncotype DX, the 21-gene assay that has dominated risk stratification for years, is no longer the only option on the shelf. The technical reality is that a small family of competing tests has emerged, each taking a slightly different path to the same destination: telling patients and their doctors who can safely skip chemotherapy and who cannot.
MammaPrint, developed by Agendia, secured FDA approval in 2007 and uses a 70-gene signature validated for early-stage breast cancer. Prosigna, built by NanoString Technologies around the PAM50 gene set, received FDA clearance in 2013.
EndoPredict, from Myriad Genetics, combines a 12-gene molecular score with traditional clinical factors. Each offers an alternative approach to risk stratification, and some provide additional prognostic information for specific subgroups. The clinical evidence base that established Oncotype DX as the most widely used test came from two landmark studies: TAILORx and RxPONDER.
Those trials gave the 21-gene assay a formidable evidence advantage. Yet ongoing research aims to refine risk prediction further, and the newer tests are increasingly part of the conversation.
Under the Hood
The detail that matters in these tests is what they measure. Oncotype DX quantifies the expression of 16 cancer-related genes and five reference genes. MammaPrint looks at 70 genes to classify tumours as low or high risk.
Prosigna uses the PAM50 gene set to produce a risk of recurrence score at 10 years. EndoPredict folds a 12-gene molecular score together with tumour size and nodal status.
As ever, the choice between them often comes down to the specific clinical question. Some tests perform better for certain tumour subtypes or patient age groups. None is perfect.
The Next Frontier
Liquid biopsy tests, which analyse circulating tumour DNA from a simple blood draw, are being investigated for monitoring recurrence after treatment. That would represent a shift from the current paradigm, where tissue from the original biopsy or surgery is the material for genomic analysis. The cost of genomic testing has decreased over time, with some tests now priced below $3,000.
That matters because cost was historically a barrier to wider adoption, particularly outside major academic centres. The National Cancer Institute is funding research to integrate genomic testing with artificial intelligence, aiming to improve prediction models beyond what gene expression data alone can achieve.
The future of personalised breast cancer treatment includes combining genomic test results with clinical data, imaging, and patient preferences to optimise therapy. The American Society of Clinical Oncology and the National Comprehensive Cancer Network continue to update their guidelines as new evidence emerges. For now, the genomic testing landscape for breast cancer is more crowded than it was a decade ago, and the evidence base is still filling in.
That is progress, even if it makes the oncologist’s job a little harder.
