Circadian Rhythm and Concentration of Melatonin in Breast Cancer Patients.
Study Goal
To review studies evaluating the circadian rhythm of melatonin in breast cancer patients and assess the effects of surgery and chemotherapy on melatonin secretion.
Results Summary
Breast cancer patients maintain a circadian rhythm of melatonin secretion, though with reduced nocturnal peaks and amplitude. Melatonin levels influence estrogen receptor concentrations, correlate with clinical symptoms, and are altered by chemotherapy and surgery.
Population
Patients with breast cancer
Effective Dosage
Not specified
Duration
Not specified
Interactions
None mentioned
| Intervention | Direction | Endpoint | Population | Dosage | Impact | Claim # |
|---|---|---|---|---|---|---|
- | increase | risk of breast cancer | - | high | associated with | #1 |
Melatonin | decrease | breast cancer growth and proliferation | - | - | display anti-proliferative effects on | #2 |
- | no change | melatonin secretion | Patients with breast cancer | - | maintain a circadian rhythm of | #3 |
- | decrease | nocturnal melatonin peak | these patients | - | reduction in | #4 |
- | decrease | melatonin circadian rhythms | these patients | - | decreased amplitude of | #5 |
Melatonin levels | neutral | estrogen receptor concentrations | hormone-dependent estrogen-positive breast cancer | - | can influence | #6 |
Chemotherapy | neutral | melatonin levels | - | - | alters | #7 |
breast surgery | neutral | melatonin secretion | - | at first-day post-operation | tends to alter | #8 |
Melatonin levels | neutral | clinical and psychological symptoms of breast cancer | - | - | correlate with | #9 |
- | neutral | Circadian rhythm and the concentration of melatonin in the blood | patients with breast cancers | - | are altered in | #10 |
melatonin's antioxidant effects | neutral | the effect of therapies | - | - | can be modulated | #11 |
BACKGROUND: Melatonin is a biomarker of the central circadian clock and its chronobiotic actions entraining circadian rhythms to the light-dark cycle are well known. Reduction in melatonin levels and altered circadian rhythms have been associated with a high risk of breast cancer. Melatonin has also been shown to display anti-proliferative effects on breast cancer growth and proliferation. Evaluation of melatonin circadian rhythm alterations in patients bearing breast cancer may have interesting prognostic and therapeutic applications. OBJECTIVE: To review studies evaluating the circadian rhythm of melatonin in breast cancer patients. The effects of surgery and chemotherapy on melatonin secretion were also reviewed. METHODS: Electronic databases, including PubMed/MEDLINE and Scopus, were searched from their inception to May 2020, using the keywords "Melatonin", "Circadian rhythm" and "Breast cancer". RESULTS: Patients with breast cancer maintain a circadian rhythm of melatonin secretion with relatively high levels during the night and low levels during the day, however, a reduction in nocturnal melatonin peak and decreased amplitude of melatonin circadian rhythms in these patients have also been reported. Melatonin levels can influence estrogen receptor concentrations in hormone-dependent estrogen- positive breast cancer. Chemotherapy alters melatonin levels and breast surgery tends to alter melatonin secretion at first-day post-operation. Melatonin levels correlate with clinical and psychological symptoms of breast cancer, such as sleep quality and depression severity. CONCLUSION: Circadian rhythm and the concentration of melatonin in the blood are altered in patients with breast cancers, and it can modify not only the sleep-wake cycle and, thus, patients' quality of life but due to melatonin's antioxidant effects, the effect of therapies can be modulated. Due to the heterogonous protocols used to assess melatonin and variable environmental factors during sampling, further studies need to control, such variables in order to tailor clinical trials based on melatonin rhythm adjustment and/or supplementation in breast cancer patients.