Test could spare breast cancer patients unnecessary chemotherapy

A gene test may improve the way doctors treating women with early-stage breast cancer identify those who can safely avoid post-surgery chemotherapy.

The initial results of the MINDACT clinical trial show the MammaPrint test, which looks at a 70-gene signature inside cancer cells, can detect which patients benefit from adjuvant chemotherapy.

The randomised trial was run by the European Organisation of Research and Treatment of Cancer, with support from a range of organisations, including Cancer Research UK. 

It compared the ability of the MammaPrint test to identify who would most benefit from chemotherapy, with that of traditional clinical assessments. 

“We’re essentially comparing analysis of tumour biology, with analysis of tumour anatomy,” said study leader Dr Martine Piccart, head of the Medicine Department at Brussels’ Jules Bordet Institute.

The study enrolled 6693 patients, who were followed up for five years on average. The results suggest that using MammaPrint would lead to a 14 per cent reduction in prescriptions of chemotherapy, with no change in survival.

Professor Arnie Purushotham, Cancer Research UK’s senior clinical advisor, said: “This important trial looked at treatment decisions made based on the genetic make-up of tumours in women with early breast cancer. It showed that fewer patients were prescribed chemotherapy when the MammaPrint test was used. 

“This approach allows us to better select patients for chemotherapy and only treat women who will respond while avoiding treating those who won’t benefit, thereby sparing them potential side-effects.”

Many women with early-stage breast cancer undergo chemotherapy after surgery to cut the risk of the disease recurring. 

The patient’s age, as well as the stage and grade of their tumour are among the factors normally taken into account before a decision on whether to recommend chemotherapy is taken. 

But Piccart said it was known that not all those undergoing chemotherapy need the treatment. Some gain no clinical benefit, while having severe side effects. 

Piccart, who is also co-founder of the Breast International Group, says if the trial shows the MammaPrint test is better at identifying patients who do not need chemotherapy than traditional methods it could help change clinical practice. That, she adds, would enable many women to be spared the aggressive treatment.  

Piccart said her team will continue to follow the patients taking part in the trial to monitor their long-term outcomes. 

The results of the study were presented to the American Association for Cancer Research’s annual meeting. 

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