Breast cancer medicines may force some cancer cells into 'sleeper mode', allowing them to potentially come back to life years after initial treatment, Medical Xpress reports.

These are the early-stage findings from scientists at Imperial College London, who studied human breast cancer cells in the laboratory.

The team, who studied a group of breast cancer drugs called hormone treatments, say their research opens avenues for finding ways of keeping the cancer cells dormant for longer, or even potentially finding a way of awakening the cells so they can then be killed by the treatment.

Dr. Luca Magnani, lead author of the study from Imperial's Department of Surgery and Cancer said: "For a long time scientists have debated whether hormone therapies—which are a very effective treatment and save millions of lives—work by killing breast cancer cells or whether the drugs flip them into a dormant 'sleeper' state.

"This is an important question as hormone treatments are used on the majority of breast cancers. Our findings suggest the drugs may actually kill some cells and switch others into this sleeper state. If we can unlock the secrets of these dormant cells, we may be able to find a way of preventing cancer coming back, either by holding the cells in permanent sleep mode, or be waking them up and killing them."