Scientists at Imperial College London and the European Institute of Oncology in Milan have discovered a new mechanism by which some ER-positive breast cancers develop resistance to anti-hormone treatments known as aromatase inhibitors.
The study, published in Nature Genetics, compared samples from 150 patients with secondary breast cancer, analysing their primary breast tumours previously collected at surgery against their secondary tumours. In one in five patients treated with aromatase inhibitors, cancer cells in their secondary tumours exhibited multiple copies of the gene for aromatase.
The findings suggest cancer cells are able to use a compensatory mechanism to counteract the effect of aromatase inhibitors and become resistant to treatment. By increasing the amount of aromatase enzyme, cancer cells can increase production of oestrogen, the hormone which drives the growth of ER-positive breast cancer.
Dr Richard Berks, Senior Research Communications Officer at Breast Cancer Now, said:
“This reveals a new way that the most common breast cancers can survive anti-hormone treatments.
“By producing more aromatase, breast tumours could resist treatment and return elsewhere around the body, years or even decades after the disease first appeared. Once breast cancer spreads, it sadly cannot be cured, and so we urgently need to tackle drug resistance.
“It is now critical we find ways to spot, at an early stage, whether a person’s breast cancer is becoming resistant to treatment so that they can be moved onto more effective options.”