If you’re taking Tamoxifen following breast cancer, have you wondered how well it’s working to protect you from cancer recurrence?

There’s no actual way to measure the effectiveness of Tamoxifen while you’re taking it.  However, researchers have identified a factor that strongly influences the effectiveness of Tamoxifen.  It turns out that the effectiveness of Tamoxifen may be closely tied to your melatonin level.1

Melatonin is a hormone naturally produced by your pineal gland (under your brain) when it gets dark in the evening.  It induces sleepiness and kicks off your body’s “nightshift” processes, which include hormone regeneration and repair of tissues from daily wear and tear.   It has also, on its own, been demonstrated to have anticancer effects.1

To generate optimal amounts of melatonin, it’s important to sleep in a very dark room.  Even small amounts of light in the room you sleep in can significantly reduce your melatonin production. (This may be one of the reasons that people who work night shifts have higher rates of cancer. 2,3) Melatonin production also declines with age.

The new research, conducted on mice, revealed that mice who slept in the darkest conditions, and therefore had the highest levels of melatonin, experienced dramatic rates in tumor regression while on Tamoxifen.  In mice whose melatonin levels were suppressed due to nighttime light exposure, tumors were barely affected by the presence of Tamoxifen.

These findings imply that to receive the full benefit of Tamoxifen, you need to be sleeping adequate hours in complete darkness.

If you’re on Tamoxifen, here’s what you can do now to increase your chances of deriving its full protective benefit:

Ironically, Tamoxifen produces hot flashes in many women, which in turn interfere with sleep.  That’s another good reason to keep your bedroom very dark.  Even if you’re not actually sleeping, you’ll continue to produce melatonin if you lie quietly in complete darkness.  That may be a great time to practice deep, intentional breathing or a gratitude meditation, either of which may help you get back to sleep.

Sweet dreams!

1 Dauchy RT et al, Circadian and melatonin disruption by exposure to light at night drives intrinsic resistance to tamoxifen therapy in breast cancer,  2014 Aug 1;74(15):4099-110. PMID: 25062775

2 AA Zamfir Chiru et al, Melatonin and cancer, J Med Life, Sep 15, 2014; 7(3): 373–374. PMCID: PMC4233441

3 He C et al, Circadian disrupting exposures and breast cancer risk: a meta-analysis, Int Arch Occup Environ Health. 2014 Sep 27. PMID: 25261318

4 Jia Y et al, Does night work increase the risk of breast cancer? A systematic review and meta-analysis of epidemiological studies, Cancer Epidemiol. 2013 Jun; 37(3):197-206. PMID: 23403128