Breast cancer is more likely to spread during sleep

The immune system is heavily modulated by the body’s sleep-wake cycle, known as the circadian rhythm.

(Christa Lesté-Lasserre/ New Scientist) — Breast cancer cells spread to other parts of the body mostly at night while people are sleeping, and not continuously throughout the day as scientists had previously thought.

This doesn’t mean that people with cancer should try to avoid sleeping to stop it from spreading, researchers warn – previous work has suggested that disrupted sleep could worsen breast cancer prognosis. But the discovery does indicate that considering the best time of day to give cancer therapies could make them more effective, says Nicola Aceto at ETH Zurich in Switzerland.

“Most cancer treatments are not designed with the intent to target tumour cells at a specific time, but are rather given with the general thought that the tumour is there, and you try to attack it at any time,” he says. “Now we understand what happens at different times better than we did before, and that [treatment] needs to be done better.” (…)