MS-N155 · Defined mushroom extract · Gastric cancer · Historical randomized evidence · Appraised 27 October 2026

Did pharmaceutical-grade PSK improve recurrence or survival when added to older adjuvant chemotherapy after curative gastric-cancer surgery?

Evidence at a glance

• Evidence label: Positive historical randomized signal; uncertain relevance to modern treatment
• Benefit: A 262-person Japanese trial reported higher five-year disease-free survival and overall survival with PSK added to mitomycin/fluorouracil.
• Certainty: Moderate for that historical regimen, low for today’s care or retail turkey-tail products.
• Risk: PSK is a defined protein-bound polysaccharide preparation, not interchangeable with culinary mushrooms, generic turkey-tail powder, PSP or mixed mushroom supplements.

What was studied

At 46 Japanese institutions, 262 patients after curative gastrectomy were randomized to standard adjuvant mitomycin plus oral fluorouracil with or without PSK.

What the evidence found

Five-year disease-free survival was 70.7% with PSK versus 59.4% without (P=0.047); five-year overall survival was 73.0% versus 60.0% (P=0.044). The trial predates modern staging, surgery, S-1/capecitabine-oxaliplatin regimens, targeted therapy and immunotherapy.

How to interpret it

This is genuine human outcome evidence for one standardized product and one historical treatment context. It does not establish that an over-the-counter turkey-tail capsule improves outcomes or that PSK adds benefit to modern adjuvant therapy.

Practical safety context

Do not substitute mushrooms for recommended postoperative therapy. Product identity, contamination, allergy, liver function and potential immunologic or drug interactions should be reviewed. Availability and regulatory status differ by country.

Questions for the care team

• Is the proposed product actually the studied PSK preparation?
• How different is today’s adjuvant regimen from the historical trial?
• Could a supplement interfere with treatment or delay evidence-based therapy?

Funding and conflicts

Funding and conflicts were not reported in the PubMed abstract; the 1994 trial involved a defined Japanese pharmaceutical product. Historical reporting standards limit conflict appraisal.

Sources

• Randomized gastric-cancer trial (PMID 7910230)
• NCI PDQ: Medicinal Mushrooms
• GI-cancer network meta-analysis (PMID 29179503)

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.