Avoid the Nightlight! It can lead to Tamoxifen Resistant Cancer

Being exposed to light at night when you are being treated for breast cancer can lead to a tamoxifen resistant cancer.

Breast cancer is the most common cancer form with about 1.7 million new diagnoses every year (2012). A common drug prescribed to breast cancer patients is called Tamoxifen. It works by blocking the receptor for estrogen in the breast tissue which prevents the cancer from growing. The most common form of breast cancer is dependent on the hormones estrogen and progesterone to keep growing at a  fast rate and by blocking it you can stop the cancer from spreading. In a new study the researchers investigated if exposure to light can have a negative effect on cancer treatment.

tamoxifen resistant cancer

A MRI image of a breast cancer tumor

Nighttime light leads to Tamoxifen resistant cancer

The study setup was to let one group of laboratory mice be exposed to a night time dim exposure of light while the control group was able to sleep in darkness. The mice that were exposed to dim light during the night produced less melatonin, a hormone linked to sleep. This lack of the hormone caused breast cancer tumors to grow faster and the tumors to develop a resistance to the drug Tamoxifen. This result was not observed in either the controls or mice subjected to the light but still getting melatonin supplements during their dimly lit night cycle.

The light used by the researchers was not very bright, just a measly 0.2 lux about the amount of light that come in through the crack of a door to an otherwise dark room. Since mice are more sensitive to light than humans it is unsure how much light is needed before the same effect can be seen there, but the scientist are working on a clinical trial for humans.

So if you are currently receiving Tamoxifen therapy for breast cancer it might be a good idea to make sure you sleep in a pitch black room to avoid developing resistance to the drug. Supplementation with Melatonin might be a good idea but if taken at the wrong time it will screw up your day/night rhythm causing further problems.

Cover image a molecule of Tamoxifen by Fuse809