A randomized, placebo-controlled trial of melatonin on breast cancer survivors: impact on sleep, mood, and hot flashes

Randomized, double-blind, placebo-controlled trial conducted at Dana-Farber Cancer Institute in Boston, USA. In the melatonin arm, 48 postmenopausal women with a history of non-metastatic breast cancer who had completed active cancer treatment were randomized; mean age was 59 years (range 48-80).

Melatonin 3 mg orally nightly at 9 p.m. for 4 months, compared with placebo.

Melatonin improved subjective sleep quality versus placebo over 4 months. The PSQI total score improved more in the melatonin group than in the placebo group (change -1.9 vs -0.1; overall p=0.001), with the main benefit reflected in fewer sleep problems and less daytime dysfunction. There were no significant differences for depressive symptoms (CES-D p=0.66) or hot flashes, including total hot flash score (p=0.19) and mean number/day (p=0.28). The regimen was well tolerated, with no grade 3/4 toxicities; common grade 1/2 adverse effects included headache, fatigue, and bad dreams.

The intervention was evaluated in a single-center study with a modest active-arm sample size and a 4-month follow-up, which limits precision and long-term inference. Outcomes were largely patient-reported, and the trial did not show benefit for mood or hot flashes despite the sleep improvement.