Black cohosh for hot flashes after breast cancer

Evidence label: No demonstrated benefit · Clinical goal: reduce treatment-related or menopausal hot flashes

Evidence at a glance

Population: women with frequent hot flashes, many with a history of breast-cancer treatment.
Intervention: a defined black cohosh extract, 20 mg twice daily, in a phase III crossover trial.
Result: hot-flash score and frequency improved no more than with placebo.

What was studied

The phase III NCCTG N01CC1 trial randomized 132 women to two four-week periods of black cohosh and placebo in crossover order. Participants kept daily diaries; the prespecified outcome combined hot-flash frequency and severity.

An earlier randomized breast-cancer survivor trial likewise found no significant advantage over placebo for most menopausal symptoms.

What the evidence shows

At week 4, mean hot-flash score fell 20% with black cohosh and 27% with placebo (P=.53). Frequency fell 17% and 26%, respectively (P=.36). Thirty-four percent preferred black cohosh, 38% preferred placebo and 28% preferred neither.

This is symptom evidence only. Black cohosh has not been shown to treat breast cancer, prevent recurrence or improve survival.

Limits and uncertainty

Treatment periods were short, and botanical extracts are not interchangeable. The result applies to the studied preparation and dose.

The PubMed abstract and official safety summary were appraised; every manufacturing detail and longer-term subgroup result was not independently verified.

Safety and practical context

NCCIH notes rare reports of serious liver injury in people using products labeled as black cohosh, uncertain safety after hormone-sensitive cancers, and misidentified or contaminated commercial products.

Stop and seek care for dark urine, jaundice, marked fatigue or abdominal pain. Review the exact product and all medicines with the oncology pharmacist.

Questions for the care team

Is the product the same standardized extract studied in a trial?
Could liver disease, a hormone-sensitive history or another medicine change the risk?
Would a better-supported nonhormonal hot-flash treatment be appropriate?

Sources

Literature searched: October 15, 2026 · Record appraised: October 15, 2026

Educational evidence summary, not personal medical advice. Research regimens describe what was studied; they are not personal prescribing instructions and should not replace cancer treatment or individualized supportive care.