Many women with breast cancer not getting genetic test to see if chemotherapy is needed

Many women with breast cancer may be undergoing unnecessary chemotherapy because their doctors aren’t using the genetic tests that determine whether chemo is necessary for their treatment, according to a study by the Netherlands Comprehensive Cancer Centre (IKNL) in collaboration with the University of Twente. In 2024, only a third of patients received the test, NOS reports.

In the Netherlands, women over 50 with early-stage breast cancer can get the MammaPrint and Oncotype DX genetic tests to map out the tumor’s genes. Doctors use this information to predict the likelihood of the cancer’s recurrence and to determine whether chemotherapy will be beneficial.

Dutch health insurance has covered these tests since 2023. Before that, only 9 percent of eligible patients received the test. In 2024, that increased to 37 percent. But that still means that approximately two-thirds of eligible women did not get the test. That amounted to around 1,000 women in 2024, according to the researchers.

Of the people who did get genetic testing and were found to have a high risk of metastases, over 80 percent underwent chemotherapy. Of the patients with a low risk, less than 10 percent received chemotherapy. Of the patients who did not get the genetic test despite being eligible, over half underwent chemotherapy.

“This suggests that the lack of test information can lead to broader use of chemotherapy than necessary,” lead researcher Sabine Siesling told NOS. "This could mean that women are receiving chemotherapy unnecessarily."

Chemotherapy comes with severe and sometimes permanent side effects, including hair loss, memory problems, and fatigue.

The researchers have launched a follow-up study to investigate why the genetic tests aren’t being used more widely.