21-Gene Recurrence Score Assay As a Predictor of Adjuvant Chemotherapy Administration for Early-Stage Breast Cancer: An Analysis of Use, Therapeutic Implications, and Disparity Profile

Authors: Jasem, J. et. al.

Source: JCO, doi:10.1200/JCO.2015.65.0887

www.jco.ascopubs.org/content/early/2016/03/17/JCO.2015.65.0887.abstract

Traditionally, patients with breast cancer tumors of greater than 1 centimeter (about ½ inch) were offered adjuvant (postoperative) chemotherapy.  However, many of these people did not receive benefit from it.  Investigators began to search for ways to determine who would and who would not benefit from taking adjuvant chemotherapy.

Genomic Health offers a Recurrence Score (RS) assay that providers can use to guide their treatment recommendations.  A patient’s RS indicates what type of benefit (risk of breast cancer recurrence in 10 years) the patient could gain from adding adjuvant chemotherapy to her breast cancer care regimen.  It is clear that this test has greatly affected how breast cancer care is provided in this country.

The investigators in this study remarked that, although the RS assay is expected to provide more uniform care across breast cancer patients, there are opportunities for the test to actually exacerbate differences in care delivery.  They observed the impact of the RS assay use among over 143,000 women diagnosed with breast cancer between 2004 and 2012.  The RS assay was used for 54% of these subjects.

The group discovered that there were lower chances of the RS assay being used for black and other nonwhite races.  Women who had governmental health insurance were also less likely to receive the assay.  Patients being cared for at academic centers, patients with larger tumors, higher tumor grade and isolated cells in an axillary lymph node were more likely to receive the assay.  The assay was used more frequently in the later years of the study.

There are standard guidelines about using the assay.  However, assays were performed in some patients whose disease characteristics did not meet those guidelines.  The assay was more likely to be used outside of national guidelines in younger patients, black patients, patients with higher tumor grade, male patients and patients being cared for in community facilities.  Also, patients on governmental insurance had a higher chance of the assay being used outside of standard guidelines.

The group noted that some of the differences in the use of the RS assay probably reflect an increased awareness of the importance of tumor biology in decision making for breast cancer care.  Previous clinical studies and the details of RS assay results can facilitate a very individualized approach to the care of a patient, and the differences in the RS assay use may reflect this.  However, the study found notable discrepancies in RS assay use for certain populations, and more research into these differences is needed.