It would be good to know what the immune system is doing during sleep. As I understand it, metastasis is caused by a local depletion in nutrients or stress to t

It would be good to know what the immune system is doing during sleep. As I understand it, metastasis is caused by a local depletion in nutrients or stress to the tumor cells, which then try to find a new environment to occupy. If tumor-killing activity of the immune system happens primarily at night, that could explain why metastasis is also primarily at night, and may explain the discrepancy on melatonin which you just mentioned, where this study found that higher melatonin levels correlated with higher circulating tumor cell numbers, but the literature suggests that melatonin helps kill tumors.