Total darkness at night ‘can aid breast cancer treatment’

Patients undergoing treatment for breast cancer with the drug tamoxifen could benefit from minimising exposure to light at night.

A Tulane University School of Medicine study has revealed that total darkness at night stimulates production of melatonin, a substance they have found to be vital to the success of tamoxifen in treating breast cancer.

By itself, melatonin was shown to delay formation of tumours and significantly slow their growth, but the regression of cancer cells in animals with high nighttime melatonin levels during complete darkness or those receiving melatonin supplementation was even more dramatic when tamoxifen was used.

Principal investigator David Blask explained: "High melatonin levels at night put breast cancer cells to sleep by turning off key growth mechanisms. These cells are vulnerable to tamoxifen. But when the lights are on … breast cancer cells 'wake up' and ignore tamoxifen."

The findings could have significant implications for patients who are exposed to light at night due to sleep problems, night shifts or the glow emitted by computer and TV screens.

Breast cancer is the most common cancer in the UK, with around 48,000 women contracting the disease in Britain each year.