Breast Cancer Spreads More During the Night

New research shows that breast cancer metastasis (spread) occurs mainly during sleep. This finding was “striking and unexpected”, according to the researchers.

Professor and molecular oncologist Nicola Aceto works at the Swiss Federal Institute of Technology in Zurich. “This has not been shown before and, to be honest, it surprised us too,” he said.

The study's authors say the findings have potential implications for the timing of biopsies and the treatment of cancers prone to metastasis.

The study appeared on 22 June in Nature , where it was published online.

Details of the Study

Circulating tumor cells (DTH) are generally thought to enter the circulation continuously or following specific events such as surgery or physical activity. However, the processes regulating tumor cell metastasis and the possible role of circadian rhythms (the biological clock) in tumor formation remain unclear.

To better understand these processes, Aceto and colleagues collected blood samples from 30 women with breast cancer at 4.00 and 10.00, representing the body's resting and active phases, respectively.

The researchers observed that more than 78% of all the circulating tumor cells obtained were in blood samples collected during the resting phase. Researchers Harrison Ball, Sunitha Nagrath and Ann Arbor from the University of Michigan wrote in Nature News & Views that these findings were surprising.

The team also observed that key circadian rhythm hormones (such as melatonin, testosterone and glucocorticoids) regulate the formation of circulating tumor cells, and that insulin promotes tumor cell proliferation in a time-dependent manner. Thus, “the need for time-controlled approaches to the characterization and treatment of breast cancer” was revealed.

Are Changes in Treatment Close?

Ball and Nagrath say the time-dependent nature of circulating tumor cell (DTH) dynamics could substantially change how cancer patients are assessed and treated. They say the data indicating proliferation and release of circulating tumor cells during the resting phase suggest specialists may need to be more mindful about when they give certain treatments. However, both also point out that large clinical trials will be needed before circadian rhythms are incorporated into standard practice. It is also unclear whether these breast cancer findings apply to other tumor types.

Mariana G. Figueiro of the Icahn School of Medicine at Mount Sinai in New York, who was not involved in the research, agrees that if studies confirm more metastatic spread at night, “there is an opportunity to treat patients at strategic times” . Figueiro also sees a potential effect on the timing of blood collection. “I think it is important for people to focus on doing biopsies and blood work based on circadian timing,” she said.

Marleen Meyers, clinical professor of Medicine at NYU Langone's Perlmutter Cancer Center in New York, also agrees that these findings may have many clinical implications. "The most obvious is that the time of day when treatment is given could affect its effectiveness." But Meyers noted that the benefits of treating someone at night must be weighed against the drawbacks of interrupting their normal sleep–wake cycle, with a careful assessment of benefit and harm. "If this finding is clinically important, it will be difficult to incorporate into clinical treatment," she said. 

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