Genetic testing to reduce the need for post-surgery chemotherapy

20 April 2016

Promising initial results could lead to a reduction in the use of adjuvant chemotherapy for breast cancer patients.

The MINDACT clinical trial makes use of the Mammaprint genetic test to give clinicians a better idea of whether to prescribe chemotherapy after surgery (adjuvant chemotherapy). Results of the trial indicate the possibility of a reduction in the overall use of adjuvant chemotherapy with no effect on survival rates.

The Mammaprint test looks at 70 genes indicative of potential breast cancer reoccurrence. Following surgery, the test is able to determine whether a patient is at high or low risk. Normally, doctors study the extracted cancer, using various criteria, such as the appearance of the cells and the size of the tumour to assess the risk of the cancer returning. 

Patients who enrolled in the MINDACT trial were assessed using both the traditional method, and the genetic test. Out of 6,693 patients, 3,356 were categorised as high risk by the standard method. 1,550 of those were categorised as only a low risk by Mammaprint. Patients defined as high risk by both methods were prescribed adjuvant chemotherapy, patients with conflicting categorisations were randomly chosen to receive chemotherapy or not. 

Over the following five years, patients from the conflicting group had a metastasis-free survival rate of 94%, regardless of whether they had chemotherapy or not. The trial is a first of its kind, which has implications for how clinicians prescribe chemotherapy, and our understanding of breast cancer.

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