While the changes are only a few percent, with more than 40, 000 women diagnosed with breast cancer in the UK alone every year, a large proportion of whom have 'ER-positive' cancer, it could mean a significant decrease in the number whose cancer returns.

BBC: Breast cancer

Kingston said she was returning to the UK to do a film before returning to shoot the beginning of the next series of ER.

BBC: NEWS | Entertainment | ER star leaves amid 'age dispute'