Breast Cancer Spreads More Aggressively at Night, Startling New Study Finds

People with breast cancer who close their eyes at night are more likely to get the disease.

A paper published in Nature this week overturns the idea that breast cancer spreads at the same rate.

Doctors may change the way they collect blood samples from people with cancer after the result.

The need for healthcare professionals to record the time at which they perform biopsies may be indicated by the findings.

Making the data truly comparable may be possible.

An unexplained difference in the number of circulating tumor cells in samples analyzed at different times of the day was discovered by researchers.

Some of my colleagues work late in the evening or early in the morning, and sometimes they also analyze blood at odd hours.

When blood samples are most often taken, mice sleep during the day when they have a higher number of cancer cells.

Thirty women with breast cancer were studied by the Swiss researchers to find out what was happening.

The majority of circulating tumor cells were found in blood samples that were taken at night while the rest were found in daytime samples.

The same result was found when the researchers injected the mice with breast cancer cells. When the mouse was at rest, the circulating tumors were higher.

The researchers said that the cancer cells collected during the rest period were prone to metastasize, whereas circulating tumor cells generated during the active phase are devoid of the ability to spread.

Tumor cells taken from mice and humans at rest increased the expression of their genes, according to genetic analysis. It makes them better at metastasizing.

Changing the light-dark routine gave some mice jet lag. There was a huge decrease in the concentration of circulating tumor cells in the mice that were messed with.

The researchers tested if giving the mice hormones that were similar to those found in the body when they were awake would affect the number of tumors.

They injected mice with testosterone, a hormone that makes it possible to turn sugar into energy, and dexamethasone, a synthetic chemical.

There was a marked reduction in the number of circulating tumor cells in a blood sample taken during the rest period.

"Our research shows that the escape of circulating cancer cells from the original tumor is controlled by hormones such as melatonin, which determine our rhythms of day and night," says Zoi Diamantopoulou.

The paper was published in a journal.