The findings show that the 21-gene recurrence test score, approved for Medicare coverage in 2006, is being used to help direct clinical decisions in what is among the first widespread applications of personalized medicine. The Duke-led study was published in JAMA Oncology and reported in Drug Discovery & Development.
As lead author Michaela A. Dinan, Ph.D., of the Duke Cancer Institute and the Duke Clinical Research Institute explained, “The decision to get chemotherapy is very complex and personal, and it needs to be made between patients and physicians. This shows that the risk score test provides information that appears to affect to patients’ selection of treatment options in general clinical practice.”
Dinan and colleagues did a retrospective study, in which they analyzed data for 44,044 Medicare patients who had early-stage, estrogen receptor-positive breast cancer. They are patients for whom the RS assay is recommended. Of those patients, 24 percent were described as low-risk using National Comprehensive Cancer Network (NCCN) guidelines; 51.3 percent were classified as intermediate risk; and 24.6 percent were called high risk because of lymph node involvement.
In toto, 14.3 percent of patients had chemotherapy within 12 months after diagnosis. The researchers saw no overall association between having the RS assay and using chemotherapy.
However, among the different NCCN categories, there were surprising differences. RS testing was associated with decreased chemotherapy use among patients who were designated under NCCN definitions as high-risk – especially the younger Medicare patients who were between the ages of 66 and 70. Increased chemotherapy treatment was associated with test use among NCCN-designated low-risk patients.
The authors were unaware of what the RS scores were for the patients. Therefore, they were not able to ascertain whether patients in the NCCN risk categories coincided with RS risk.
Dinan concluded, “This limitation of the study affected the extent to which we could determine how the RS results were being used to guide chemotherapy within individual patients, and remains an area of ongoing research.”