MS-N156 · Defined mushroom extract · Colorectal cancer · Historical randomized evidence · Appraised 27 October 2026

Did pharmaceutical-grade PSK improve outcomes when added to older fluoropyrimidine-based adjuvant treatment after colorectal-cancer surgery?

Evidence at a glance

• Evidence label: Positive historical trials; uncertain applicability to modern adjuvant therapy
• Benefit: One 205-person randomized study reported higher five-year disease-free survival; stage III subgroup survival also favored PSK.
• Certainty: Low to moderate. Multiple Japanese trials and meta-analyses show a signal, but regimens and reporting are dated and product-specific.
• Risk: PSK cannot be equated with retail turkey-tail powder, PSP, reishi, AHCC or culinary mushrooms.

What was studied

A randomized study analyzed 205 patients with stage II or III colorectal cancer after surgery and mitomycin C. Participants received UFT 300 mg/day with PSK 3 g/day or UFT alone for two years. Older centrally randomized Japanese studies and meta-analyses evaluated similar adjunctive use.

What the evidence found

Five-year disease-free survival was 73.0% with PSK versus 58.8% without (P=0.016). Overall survival was 81.8% versus 72.1% (P=0.056). In the stage III subgroup, five-year DFS was 60.0% versus 32.1% and OS 74.6% versus 46.4%, but subgroup effects need caution.

How to interpret it

The evidence deserves acknowledgement, but it does not answer whether PSK adds benefit to current FOLFOX or CAPOX, ctDNA-guided treatment, targeted therapy or immunotherapy. It does not validate nonstandardized mushroom products.

Practical safety context

Use only after oncology review. Standard adjuvant therapy should not be delayed or replaced. Confirm exact product, manufacturing quality, allergies, liver function and possible interactions.

Questions for the care team

• Does any modern trial combine verified PSK with the current regimen?
• Is the product chemically equivalent to the Japanese trial preparation?
• Are recurrence and survival—not immune markers—being measured?

Funding and conflicts

Funding and conflict details were not fully verified in the older reports. The 2004 study reported mild adverse effects and good compliance; historical reporting limits certainty.

Sources

• Randomized UFT±PSK trial (PMID 14997197)
• Full trial report (PMCID PMC2409633)
• Meta-analysis of randomized trials (PMID 16133112)
• Cochrane review (PMID 36445793)
• NCI PDQ: Medicinal Mushrooms

Last literature search: 27 October 2026. Record appraisal: 27 October 2026. This page is educational and does not replace individualized medical advice. Symptom, biomarker, immune-marker or nutritional changes must not be interpreted as proof of tumor control, recurrence prevention or longer survival unless those outcomes were directly tested.