Fisetin’s reputation rests almost entirely on animal and cell work. Only one randomised controlled trial of fisetin in cancer patients has reported results. It was published in 2018, and it is small [1]. It is also easy to cite in a way that overstates what it showed.
The distinction that matters here is between a change within a group and a difference against placebo. This trial produced both, and only one of them is evidence that fisetin did something. Summaries of this study often lead with the weaker set of numbers.
Key Takeaways
- One randomised controlled trial has tested fisetin in cancer patients: 37 colorectal cancer patients on chemotherapy, 100 mg daily for seven weeks.
- Within the fisetin group, IL-8, hs-CRP and MMP-7 all fell significantly.
- Against placebo, only IL-8 reached significance. The hs-CRP and MMP-7 results did not separate from placebo.
- A 2024 systematic review concluded only that fisetin seemed to improve inflammatory status during 5-fluorouracil chemotherapy, and that the polyphenol evidence overall is inconclusive.
- The trial measured biomarkers, not clinical outcomes, and did not measure plasma fisetin.
Important: This article summarises a small biomarker trial and does not constitute medical advice. Fisetin has not been shown to treat, prevent or slow any cancer. If you are undergoing cancer treatment, do not add any supplement without discussing it with your oncology team, because flavonoids can interact with chemotherapy agents and other prescription medicines.
The design
Thirty-seven colorectal cancer patients undergoing chemotherapy were randomised in a double-blind, placebo-controlled trial [1]. Eighteen received 100 mg of fisetin daily and nineteen received placebo, for seven consecutive weeks. Supplementation began one week before chemotherapy and continued to the end of the second chemotherapy cycle.
Participants averaged 55.59 years with a standard deviation of 15.46, and 62.16% were male. The trial was registered as IRCT2015110511288N9. Plasma IL-8, IL-10, high-sensitivity CRP, MMP-7 and MMP-9 were measured by ELISA before and after the intervention.
Two features of the design are worth holding onto. The dose was 100 mg, which is at the low end of what supplement protocols suggest and far below the pulsed senolytic doses used elsewhere. And every participant was receiving chemotherapy, so this measures fisetin as an add-on during active cancer treatment, not as a supplement taken by healthy people.
What was found, stated precisely
Within the fisetin group, plasma IL-8 and high-sensitivity CRP fell significantly after the intervention, at p < 0.04 and p < 0.01 respectively, and MMP-7 was also suppressed at p < 0.02 [1]. Those are the three numbers that circulate most widely.
Compared against the placebo group, however, significant change was observed only in IL-8 concentrations, at p < 0.03 [1]. The hs-CRP and MMP-7 results did not separate fisetin from placebo.
That gap is the whole story of this trial. A within-group change tells you a marker moved over seven weeks in people receiving chemotherapy. It does not tell you fisetin moved it, because the placebo group’s markers were moving too. Only the between-group comparison isolates the treatment. On that comparison, this trial supports one thing: an effect on IL-8.
Why the within-group numbers keep getting quoted
They are more impressive, there are more of them, and they appear in the abstract before the between-group result. A reader skimming for findings encounters three significant reductions and stops. The sentence that qualifies them comes afterwards and begins with the word however.
This is not unique to fisetin. Reporting within-group significance prominently is common in small supplement trials, and it is one of the most reliable ways for a modest result to acquire a large reputation. If you see a claim that fisetin reduced CRP in cancer patients, it traces back to this trial, and this trial did not show that against placebo.
How independent reviewers read it
A 2024 systematic review of clinical evidence for polyphenols in colorectal cancer, registered on PROSPERO as CRD42024560044 and conducted according to PRISMA, screened 100 articles and retained 12 with a low risk of bias [2]. Its verdict on fisetin is deliberately narrow: fisetin seemed to improve the inflammatory status of patients under chemotherapy with 5-fluorouracil.
Note what that sentence does not say. It does not say fisetin treated cancer, slowed progression, or improved survival. The review’s overall conclusion is that the role of polyphenols in preventing or treating colorectal cancer is inconclusive and that more clinical studies under more controlled conditions are needed [2].
That is the most favourable independent reading available, and it is a cautious one. The much larger body of cell and animal work is covered in the preclinical apoptosis research, and the practical questions about timing are in fisetin during chemotherapy. It is a reasonable summary to carry away from this trial.
What is still missing
The trial measured inflammatory and matrix metalloproteinase markers, not clinical outcomes. Nobody has shown that changing IL-8 during chemotherapy changes how a patient does. Marker studies generate hypotheses; they do not answer whether a treatment helps.
Sample size is the other limit. Eighteen people received fisetin. A trial that size can detect only large effects, and a single significant between-group result in a panel of five markers is the kind of finding that needs replication before it is treated as established.
There is also the absorption question. At 100 mg of what appears to be conventional fisetin, plasma exposure would be expected to be low, given that 1,000 mg of unformulated fisetin produced a peak concentration under 10 ng/mL in healthy volunteers [3]. Whether this trial achieved meaningful exposure is unknown, because it did not measure plasma fisetin.
Common questions
Has fisetin been tested in cancer patients?
Yes, in one small randomised controlled trial. Thirty-seven colorectal cancer patients undergoing chemotherapy received either 100 mg of fisetin or placebo for seven consecutive weeks [1].
Did fisetin reduce inflammation in that trial?
Partly. Within the fisetin group IL-8, hs-CRP and MMP-7 all fell significantly, but against placebo only IL-8 reached significance at p < 0.03 [1]. The between-group comparison is the one that isolates the treatment effect.
Does this mean fisetin helps treat colorectal cancer?
No. The trial measured inflammatory and matrix metalloproteinase markers, not tumour response, progression or survival. A 2024 systematic review found the clinical evidence for polyphenols in colorectal cancer inconclusive overall [2].
Why do some sources report three significant results and others one?
Because they are quoting different comparisons. Three markers changed significantly within the fisetin group; one differed significantly from placebo [1]. Within-group change on its own is not evidence that the treatment caused it.
Was the dose unusually low?
It was 100 mg daily, which is modest compared with the pulsed protocols often discussed for senolytic use. It matches the dose in a registered trial in adults aged 50 and over [4], but is far below the 20 mg/kg used in the TROFFi trial [5].
Should cancer patients take fisetin?
This is a decision for the treating oncology team, not something to act on from a single small biomarker trial. Flavonoids can affect drug-metabolising enzymes, and chemotherapy regimens are sensitive to interactions.
References
- Effect of fisetin supplementation on inflammatory factors and matrix metalloproteinase enzymes in colorectal cancer patients. Food Funct (2018). PMID 29541713
- Polyphenols in the Prevention and Treatment of Colorectal Cancer: A Systematic Review of Clinical Evidence. Nutrients (2024). PMID 39203871
- Enhanced bioavailability and pharmacokinetics of a novel hybrid-hydrogel formulation of fisetin orally administered in healthy individuals: a randomised double-blinded comparative crossover study. J Nutr Sci (2022). PMID 36304817
- Low-Dose Fisetin Supplementation and Its Association With Chronic Inflammation in Middle-Aged and Older Adults: Study Protocol for a Triple-Blind, Randomised, Placebo-Controlled Trial. Basic Clin Pharmacol Toxicol (2026). PMID 42633989
- A phase II randomized placebo-controlled study of fisetin to improve physical function in breast cancer survivors: the TROFFi study rationale and trial design. Ther Adv Med Oncol (2026). PMID 41835341
These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure, or prevent any disease. Content is for informational purposes only and is not medical advice; consult a qualified healthcare provider before starting any supplement. As an Amazon Associate we earn from qualifying purchases.