The remedies, known as NACs (N-Acetyl cysteines), are decongestants that help people cope with the worst symptoms of the common cold—and they also happen to interfere with the growth and spread of cancer.

It's all to do with cancer cells known as stroma by interfering with cancer cells known as stroma, which are essential for cancer to spread. They are part of a process that includes special 'transporter' proteins that supply energy—and specifically lactate—from neighbouring cells.

NAC cold remedies reduce the numbers of transporter proteins by 80 per cent, researchers from the University of Salford have discovered, effectively cutting off the cancerous cells' food supply.

In laboratory tests, the researchers say they have witnessed a "near complete reduction" in the transporter genes when a cold remedy has been applied to breast cancer cells.

And they've seen the same extraordinary results in 12 women who had been waiting to have surgery for breast cancer. The women were given the maximum dose of a NAC cold remedy for three weeks, and biopsies before and afterwards revealed that the quantity of the transporter cells had reduced by 80 per cent. This almost completely halted the growth and spread of the breast cancer, and made it far less aggressive.

High levels of the transporter protein also suggest that breast cancer is likely to be fatal, the researchers added.

Discovering a highly effective and non-toxic alternative to chemotherapy is a "huge step forward", the researchers say.