The impact of the adoption of the 21-gene recurrence score (RS) assay on receipt of chemotherapy was strongly population dependent and associated with relatively lower chemotherapy use in groups with high-risk disease and relatively higher chemotherapy use in patients with low-risk disease, according to a study published online ahead of print in JAMA Oncology.1

Guidelines recommend consideration of chemotherapy for most patients with early-stage, estrogen receptor-positive, invasive breast cancer in the absence of additional prognostic information.

The RS assay has been shown in limited academic settings to reduce physician recommendations for adjuvant chemotherapy.

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Researchers examined whether adoption of the RS assay in a nationally representative sample of patients with early-stage breast cancer was associated with the use of chemotherapy.

They performed a retrospective cohort study of Medicare beneficiaries who received a diagnosis of incident breast cancer between 2005 and 2009 using Surveillance, Epidemiology, and End Results data set with linked Medicare claims to evaluate who received chemotherapy within 12 months of diagnosis.

A total of 44,044 patients met the criteria for enrollment: 24% had low-risk, 51.3% intermediate-risk, and 24.6% high-risk disease as defined by the National Comprehensive Cancer Network. Findings revealed no association between receipt of the RS assay and chemotherapy administration.

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In multivariate analysis, there was a significant interaction between NCCN risk and use of the RS assay, with assay use associated with lower chemotherapy use in high-risk patients and greater chemotherapy use in low-risk patients, compared with no receipt of the assay.

In unadjusted analyses, overall chemotherapy use decreased over time in patients 70 years or younger with high-risk disease and those receiving the assay.

In conclusion, overall use of chemotherapy decreased during the study period in patients who were most likely to receive chemotherapy.


  1. Dinan MA, Mi X, Reed SD, et al; Association between the use of the 21-gene recurrence score assay and receipt of chemotherapy among Medicare beneficiaries with early-stage breast cancer, 2005-2009. [published online ahead of print August 27, 2015]. JAMA Oncol. doi: 10.1001/jamaoncol.2015.2722.