Breast Cancer Treatment With Tamoxifen Requires Total Darkness at Night

breast cancer

Breast cancer treatment with a drug called Tamoxifen was shown to require total darkness at night to be effective. Even low levels of light in the bedroom at night were shown to affect melatonin, a hormone that plays a role in sleep and setting the circadian rhythm. Melatonin levels were reduced with even the smallest amount of light and this was shown to be associated with larger tumors and resistance to Tamoxifen.

Getting enough sleep has increasingly been shown to be important in maintaining health. The body has a daily biological rhythm, called the circadian rhythm, and maintenance of a regular circadian rhythm is important for health. Disruption of the regularity of this rhythm due to travel, shift changes or other factors has been associated with many changes in biochemistry that have been suggested to lay the basis for some diseases or states of ill health.

In this latest study, it was shown that even a very small amount of light, such as from a cell phone or computer, can play a role in disturbing the circadian rhythm and related hormone levels. In the experimental set up for this study, the dim amount of light that produced the effect was equivalent to the faint amount of light that shines in at the bottom of a door. It has been known for a long time that melatonin is a very important hormone in maintaining the circadian rhythm and, in this study on breast cancer; melatonin levels were shown to be disrupted.

It has been shown that the higher melatonin levels that occur at night put breast cancer cells in a state of sleep and in this sleep state, growth mechanisms are turned off. This is when the cancer cells are killed by the drug Tamoxifen. However, if light is present and the melatonin levels are suppressed, then the cells do not enter the sleep state and are not affected by the Tamoxifen.

The study that was published in the journal Cancer Research was carried out on rats. The rats had breast cancer and they were being treated with Tamoxifen. Some of the rats slept in complete darkness through the night and other rats slept in a space that had a dim light level. The rats that slept in the presence of a dim light had larger tumors and the tumors were shown to be resistant to Tamoxifen. In a second stage of the experiment, the mice that slept in a dimly lit space were given melatonin supplements and the results from this experiment showed the Tamoxifen worked better and the tumors were smaller. The study was carried out at Tulane University School of Medicine and Dr. Steven Hill led the research team.

It has been reported that Dr. Hill does not advocate use of melatonin supplements in humans, based on the results of his study, but the research does suggest that it may be wise for women with breast cancer to sleep in a completely darkened room, or sleep with a blindfold, while taking Tamoxifen as a treatment. While Tamoxifen is a drug that has been used as a standard treatment for breast cancer in women, it does not work well in some women. The recently published paper may have provided the answer to why this is happening. It is possible that these women have lifestyles and bedtime practices that are the most disruptive to the circadian rhythm. Of course, extending the research study to humans is planned for the future. It is good to know at this point, however, that good sleeping habits and total darkness at night might be beneficial when receiving treatment for breast cancer.

By Margaret Lutze

Cancer Research
Medical Daily
BBC News