Use of Recurrence Assay in Guiding Chemotherapy Decisions

In a new study of Medicare beneficiaries published in JAMA Oncology, researchers found that use of the 21-gene recurrence score (RS) assay was associated with decreased use of chemotherapy in high-risk patients and increased use of chemotherapy in low-risk patients compared with not using the test.

National Comprehensive Cancer Network (NCCN) guidelines recommend consideration of adjuvant chemotherapy in estrogen receptor (ER)-positive, node-negative breast cancer for all but the smallest tumors. The RS assay has been shown in limited academic settings to reduce physician recommendations for adjuvant chemotherapy. However, it is unknown whether adoption of the assay has reduced overall chemotherapy use among practitioners in general. Michaela Dinan, PhD, Duke Clinical Research Institute (Durham, NC), and her team examined associations between the adoption of the RS assay and chemotherapy in a nationally representative sample of Medicare beneficiaries with early-stage breast cancer.

For the study, the Surveillance, Epidemiology, and End Results (SEER) database linked with Medicare claims to identify patients diagnosed with early-stage, ER-positive, nonmetastic breast cancer between 2005 and 2009. Patients were required to have a primary diagnosis of breast cancer on a Medicare claim between 2 months before and 4 months after the SEER-reported diagnosis. A total of 44,044 patients had low-risk (24.0%), intermediate-risk (51.3%), or high-risk disease (24.6%), as defined by the NCCN guidelines, and met the study criteria.  

Overall, 14.3% of patients received chemotherapy within 12 months after diagnosis. The researchers observed no overall association between receipt of testing and chemotherapy use. Chemotherapy was more frequently used in patients aged 70 and younger, patients with fewer comorbidities, and patients with high-risk disease. There was, however, a significant interaction between use of the assay and NCCN-defined risk. Genetic testing in high-risk patients was associated with decreased use of chemotherapy (odds ratio [OR], 0.36; 99% confidence interval [CI], 0.26-0.50) and in low-risk patients  was associated with increased use of chemotherapy (OR, 3.71; 99% CI, 2.30-5.98), compared with patients that did not receive genetic testing (P=.006 for the overall interaction).

Because of the significant impact of age on use of the RS assay and chemotherapy, a subgroup analysis of patients aged 66–70 years was performed. The researchers observed an overall decrease in the use of chemotherapy, from 29.1% in 2005 to 24.0% in 2009; this appeared to be limited to patients with high-risk disease and patients who underwent RS assay testing. The extent to which decreased chemotherapy use is influenced by genetic testing use, as opposed to unrelated changes in practice, could not be determined, the authors noted.

“Our data suggest that use of the RS assay may have decreased chemotherapy use in general practice among younger patients with high-risk disease in whom receipt of chemotherapy would have otherwise been likely, but that it was associated with greater chemotherapy use in patients with low-risk disease,” wrote the researchers.—Eileen Koutnik-Fotopoulos

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Dinan MA, Mi X, Reed SD, Lyman GH, Curtis LH. Association between 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.