High-Dose Melatonin

Pineal hormone with dual roles in circadian support and emerging anti-tumor / adjuvant activity

Key Points

• Melatonin is a pineal hormone regulating circadian rhythm; oncology interest centers on higher pharmacological doses (10–20 mg) rather than the low doses used for sleep.
• Multiple small RCTs and meta-analyses suggest melatonin added to chemotherapy may improve tumor response and 1-year survival and reduce toxicity — but trials are small and mostly from one research group.
• Proposed anti-tumor mechanisms include anti-angiogenic (VEGF suppression), pro-apoptotic, antioxidant, anti-estrogenic (aromatase and estrogen-receptor modulation), and immune-enhancing effects.
• Strong supportive-care evidence for improving sleep, reducing chemotherapy-related fatigue, and mitigating radiation dermatitis and mucositis.
• Circadian disruption and low nocturnal melatonin are epidemiologically linked to higher breast and colorectal cancer risk (shift-work data).
• Very safe even at high doses; main effects are drowsiness and vivid dreams — but the anti-tumor survival data need confirmation in large trials before firm recommendations.

Background and Mechanism

Melatonin (N-acetyl-5-methoxytryptamine) is secreted by the pineal gland in response to darkness and is the principal hormonal signal of the circadian system. In oncology, interest extends well beyond sleep to its **pharmacological, higher-dose effects** on tumor biology and treatment tolerability. Proposed anticancer mechanisms are broad: - **Anti-angiogenic:** downregulates VEGF and hypoxia-inducible factor signaling. - **Pro-apoptotic and anti-proliferative:** modulates cell-cycle regulators and can enhance apoptosis in tumor cells. - **Anti-estrogenic:** melatonin is a "selective…

Clinical Evidence

**Adjuvant to chemotherapy (anti-tumor signal):** A frequently cited systematic review and meta-analysis (Seely et al., Integr Cancer Ther 2012) of 8 RCTs (n=761), predominantly in advanced solid tumors, reported that melatonin (usually 20 mg/night) added to chemotherapy was associated with improved 1-year survival (relative risk of death reduced) and higher rates of tumor response and disease control, along with reduced chemotherapy toxicity (thrombocytopenia, neuropathy, fatigue). Importantly, much of this evidence originates from a single Italian research group (Lissoni et al.), and…

Dosing and Clinical Applications

**Circadian/sleep support:** Low doses (0.5–3 mg) taken 30–60 minutes before bedtime are used for sleep and jet-lag–type disruption common during treatment. **Oncology (pharmacological) dosing:** Trials investigating anti-tumor and toxicity-reducing effects generally used **10–20 mg at night**, taken concurrently with chemotherapy or radiation. Because of its sedative effect, evening dosing is standard and also aligns with physiological rhythm. **Practical applications:** - As supportive care for sleep disturbance, fatigue, and possibly radiation-induced mucositis/dermatitis — reasonable and…