Melatonin, the hormone known for its ability to regulate your sleep and wake cycle, has long been the focus of sleep studies in the medical world. Though its natural secretion comes from the pineal gland in the brain, melatonin is also taken as an oral supplement to treat sleep disorders like insomnia or help lessen jetlag symptoms.

Recent oncological research is now suggesting a correlation between melatonin and cancer: studies have found that it could have a potential ability to lessen the negative effects of cancer chemotherapy, enhance its therapeutic effect and reduce its toxicity (1). What is melatonin’s main mechanism, and how does it work with chemotherapy to lessen symptoms and improve outcomes?

Melatonin secretion from the pineal gland plays an integral part to the body’s natural circadian rhythm, regulating sleep and cueing our bodies to fall asleep when it’s dark outside. Because of this, melatonin is one of the body’s strongest antioxidants. Experimental studies have indicated that melatonin may inhibit cancer cell growth, and preliminary clinical studies perhaps confirm its anticancer properties (2). One clinical investigation looked to define the therapeutic properties of melatonin and conducted two studies on the matter. The first evaluated the effects of melatonin in a group of 1,440 patients with untreatable advanced tumors who either received supportive care with or without melatonin; the second study looked at the influence of melatonin on the effectiveness and toxicity of chemotherapy (2). In both cases, patients were administered 20 milligrams per day and researchers were astonished by the results. In both studies, the percentage of patients with disease stabilization and percentage of one-year survival were both higher in patients who took melatonin, the objective tumor response rate was higher in patients treated with chemo and melatonin, and chemotherapy-induced side effects lessened with melatonin (2). Clearly more research needs to be conducted to confirm findings but preliminary glimpses into what melatonin might be capable of has been clinically interesting.

In a study published in the Journal of Pineal Research, scientists evaluated the five-year survival results for 100 metastatic non-small cell lung cancer patients on chemotherapy, both with and without the concomitant administration of melatonin at 20 milligrams per day. Their research indicated noteworthy results—both the overall tumor regression rate and the five-year survival rate were significantly higher in patients who took melatonin (1). None of the patients treated with chemo alone were alive after two years, but a five-year survival was achieved in three of 49 (6 percent) patients treated with both (1).

A separate study conducted by researchers at the Division of Radiation Oncology at the Hospital S. Gerardo in Milan further examined melatonin’s effect on patients in combination with chemotherapy treatment and found that melatonin seemed to potentially exert anticancer activity in three ways: inhibiting cancer cell growth in cells expressing melatonin receptors; stimulation of the antitumor immune response; and lessening the strength of oncogene expression (3). The study considered 370 patients suffering from cancer who were randomized to receive chemotherapy alone or with chemotherapy and 20 milligram doses of melatonin, taken at night time. The study found that the overall tumor regression rate and two-year survival rate was significantly higher for those concomitantly treated with melatonin and chemo (3).

More studies have been conducted that further suggest melatonin’s support or enhancement of chemotherapy by acting as an antioxidant agent that reduces the toxicity and symptoms of treatment. Additionally, melatonin is thought to be potentially supportive in assisting effectiveness of chemotherapy but further studies are needed to confirm this (4). One included 250 metastatic solid tumor patients who were randomized to receive chemotherapy alone or in combination with 20 milligrams of melatonin per day. Scientists found that the one-year survival rate and tumor regression rate were both significantly higher in patients concomitantly treated with melatonin (4).  The same researchers conducted a related study in 2007 that confirmed their original study’s results—of 846 patients with metastatic solid tumors, those who were randomized to receive chemotherapy alongside melatonin cited an increase in disease stabilization and survival time in respect to chemotherapy alone.

Though these studies are interesting and important to consider as cancer research develops, there is undoubtedly a need for further investigation before definite conclusions can be made about melatonin’s effect on cancer chemotherapy. These early studies are motivating but require more examination before fully considering them as fact. Do not take melatonin before getting clearance by your oncologist, and always ask your oncologist or physician before making changes to your regimen.


  1. Lissoni P, Chilelli M, Villa S, Cerizza L, Tancini G. Five years survival in metastatic non-small cell lung cancer patients treated with chemotherapy alone or chemotherapy and melatonin: a randomized trial. J Pineal Res. 2003;35(1):12-5.
  2. Lissoni P. Is there a role for melatonin in supportive care?. Support Care Cancer. 2002;10(2):110-6.
  3. Lissoni P. Biochemotherapy with standard chemotherapies plus the pineal hormone melatonin in the treatment of advanced solid neoplasms. Pathol Biol. 2007;55(3-4):201-4.
  4. Lissoni P, Barni S, Mandalà M, et al. Decreased toxicity and increased efficacy of cancer chemotherapy using the pineal hormone melatonin in metastatic solid tumour patients with poor clinical status. Eur J Cancer. 1999;35(12):1688-92