Genetic Testing Associated with Decreased Use of Chemotherapy in High-Risk Patients

Decrease found in chemotherapy use among patients with high-risk cancer and those who received genetic testing.

High-risk patients used chemotherapy less than low-risk patients using the 21-gene recurrence test, according to a study published online by JAMA Oncology.

National Comprehensive Cancer Network (NCCN) guidelines state that patients should consider chemotherapy in estrogen receptor (ER)-positive, node-negative breast cancer for all but the smallest tumors. Studies in the past have suggested that the 21-gene recurrence score assay (testing) is cost-effective due to the fact that it prompts more appropriate allocation of chemotherapy to patients most likely to benefit.

Researchers at the Duke Clinical Research Institute investigated the association between adoption of the 21-gene recurrence score assay testing in a nationally representative sample of Medicare patients with early stage breast cancer and the use of chemotherapy.

The study evaluated approximately 14,000 individuals suffering from low-risk (24%), intermediate-risk (51.3%) or high-risk disease (24.6% lymph node positive) as defined by NCCN standards. The study found that 14.3% of patients received chemotherapy in the 12 months following diagnosis.

There was no observable correlation between receipt of the testing and chemotherapy use.

However, there was an interaction between NCCN risk and use of the assay. The genetic testing appeared to be associated with a decrease in chemotherapy use among high-risk patients and an increase in chemotherapy use in low-risk patients.

A subgroup analysis of the age group between 66 to 70 years of age revealed an overall decrease in the use of chemotherapy from 29% to 24% that was limited to patients with high-risk disease and patients who went through genetic testing. Authors note that they could not determine to what extent decreased chemotherapy use reflects the influence of genetic testing or unrelated changes in practice.

Scientists involved in the study also note that their results have limitations as only testing paid for by Medicare was detected in their analysis.

“Our data suggest that use of the RS [21-gene recurrence score] 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 authors of the study.

While the reason for the correlation is still unknown, the fact remains that use of the RS assay decreased chemotherapy use in high-risk patients while increasing the use of chemotherapy in low-risk patients. This anomaly needs further testing, especially in cases where testing is not paid for by Medicare, in order to confirm the findings and investigate the reasoning behind this occurrence.