Key messages
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Due to a lack of robust evidence, the effects of melatonin on quality of life and sleep quality in people receiving treatment for cancer are unclear.
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Melatonin might not increase the risk of adverse events, but the available evidence is not strong enough for us to be certain.
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Well designed studies using melatonin over a period of up to three months are needed to give better estimates of the benefits and risks.
What is melatonin?
Melatonin is a hormone produced in the body to regulate the daily sleep and wakefulness cycle. It has been suggested that melatonin may improve sleep quality and quality of life, which are very important in cancer treatment. Moreover, there is research suggesting that melatonin is effective against solid tumours and may be effective for the treatment of cancer.
What did we want to find out?
We wanted to find out if melatonin can be used in cancer treatment, particularly for preserving the quality of life and sleep quality of cancer patients. We also wanted to find out if melatonin causes any unwanted side effects ('adverse events').
What did we do?
We searched for studies that looked at melatonin used with other standard cancer treatments compared with standard cancer treatments used alone or with placebo (fake treatment).
What did we find?
We found 30 studies that involved 5093 cancer patients, both men and women, with cancer of any type. The studies were conducted in 10 countries around the world.
We focused on the effects of melatonin over a period of three months. When compared to placebo plus standard cancer treatments, it is unclear if melatonin has an effect on quality of life and sleep. Melatonin may have little to no effect on potential adverse events like headache, fatigue, and nausea, but we are very uncertain about these results. No results are available for dizziness.
We found no studies to help us answer our questions about quality of life and sleep quality when melatonin is used with standard cancer treatments compared to the standard treatment alone. However, the studies did evaluate potential adverse events that might be related to melatonin, and they found that melatonin probably reduces the risk of tiredness (fatigue), and may reduce the risk of feeling sick (nausea). It is unclear if melatonin has an effect on headaches. No results are available for dizziness.
When melatonin is used topically, such as in a cream to put on the skin or in a mouth wash, it is unclear if it has an effect on quality of life. We found no studies to help us answer our questions about sleep quality. No data are available for adverse events like headache, fatigue, nausea, and dizziness, as these are not relevant if the melatonin is used topically. It is unclear if melatonin has any other unwanted effects when used topically.
What are the limitations of the evidence?
We are not confident in the evidence because it is possible that people in the studies were aware of which treatment they were getting. The evidence relating to some benefits and risks we are interested in does not cover all cancer types, or it is based on only a few cases.
How up to date is this evidence?
The evidence is up-to-date to September 2024.
The available evidence is of very low certainty, so we are unable to draw conclusions about the effects of melatonin on quality of life and sleep at three months in people receiving treatment for cancer. There may be no difference in adverse events between melatonin plus standard treatment and placebo plus standard treatment, but the evidence is very uncertain. Data were lacking for some outcomes, such as dizziness. Melatonin used alongside standard treatment probably reduces the risk of fatigue and may reduce nausea when compared to standard treatment alone. Since the evidence base for melatonin in people with cancer is limited due to insufficient data and risks of bias in study design, the decision for or against using melatonin as an adjunct to cancer treatment cannot easily be made at the current time.
To evaluate the benefits and harms of melatonin for preserving health-related quality of life and sleep in cancer patients.
To identify studies for inclusion in this review, we used CENTRAL, MEDLINE, 10 other databases, and four trial registers, together with reference checking, citation searching, and contact with study authors. The latest search date was 10 September 2024.
This Cochrane Review was partially funded by AG Biologische Krebstherapie, Deutsche Krebshilfe (grant numbers 70-301 and 109863). The funding agency had no role in the design or conduct of the study.
The protocol for this review is available via DOI 10.1002/14651858.CD010145.