# PSK (Krestin) mushroom polysaccharide as adjuvant therapy

Source: https://onco.cc/technologies/psk-krestin-adjuvant/  
OnCo record `psk-krestin-adjuvant` (Technology). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

PSK, a protein-bound polysaccharide from the turkey tail mushroom, has been an approved adjuvant cancer drug in Japan since 1977. Meta-analyses of Japanese randomised trials in stomach and bowel cancer found a modest survival benefit added to chemotherapy, but these results have never been tested outside Japan.

## Summary

Polysaccharide-K (PSK, Krestin) is extracted from Trametes versicolor (turkey tail) and approved in Japan as an adjuvant to chemotherapy after gastric and colorectal cancer surgery. A meta-analysis of eight randomised trials with 8,009 patients with curatively resected gastric cancer (Oba et al., 2007) found improved overall survival with PSK added to chemotherapy (hazard ratio 0.88), and a meta-analysis of three trials in colorectal cancer (Sakamoto et al., 2006) reported improved overall and disease-free survival. All trials were Japanese, most are decades old, chemotherapy backbones are outdated, and no Western trial has been done, so regulators outside Japan have not approved it. The NCI PDQ medicinal mushrooms summary describes the evidence as promising but limited to Japan. PSK is well tolerated; over-the-counter 'turkey tail' supplements are not PSK and are unstandardised.

## Fields

- Kind: Technology
- Status: approved
- Last checked: 2026-09-10
- Tags: complementary; supportive-care; evidence:moderate
- Principle: Beta-glucan polysaccharides bind dectin-1 and toll-like receptors on innate immune cells, enhancing dendritic cell and NK activity and shifting cytokine balance toward anti-tumour immunity.
- Since: 1977
- Strengths: Approved drug with randomised trials and meta-analyses; Good tolerability; Plausible innate immune mechanism
- Limitations: All evidence from Japan with old chemotherapy regimens; No Western confirmatory trial; Supplements sold as turkey tail are not PSK

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Polysaccharide-K
- Efficacy of adjuvant immunochemotherapy with PSK for curatively resected gastric cancer: meta-analysis of 8,009 patients (Cancer Immunol Immunother 2007): https://doi.org/10.1007/s00262-006-0248-1
- PSK adjuvant immunochemotherapy in curatively resected colorectal cancer: meta-analysis (Cancer Immunol Immunother 2006): https://doi.org/10.1007/s00262-005-0054-1
- NCI PDQ: Medicinal mushrooms: https://www.cancer.gov/about-cancer/treatment/cam/hp/mushrooms-pdq

## Connected records

- cancers: [Colorectal cancer](https://onco.cc/cancers/colorectal/), [Gastric & gastro-oesophageal junction cancer](https://onco.cc/cancers/gastric/)
- fronts: [Immunotherapy](https://onco.cc/fronts/immunotherapy/), [Supportive Care & Survivorship](https://onco.cc/fronts/supportive-care/)
- technologies: [Cytotoxic chemotherapy](https://onco.cc/technologies/cytotoxic-chemotherapy/), [Evidence-based integrative oncology](https://onco.cc/technologies/integrative-oncology/), [Medicinal mushrooms: reishi, turkey tail, shiitake and others](https://onco.cc/technologies/medicinal-mushrooms-reishi-turkey-tail/)
- bottlenecks: [No incentive to repurpose cheap drugs](https://onco.cc/bottlenecks/b-generic-repurposing/), [Regulatory divergence between regions](https://onco.cc/bottlenecks/b-regulatory-fragmentation/)
- key papers: [Efficacy of adjuvant immunochemotherapy with polysaccharide K for patients with curative resections of gastric cancer](https://onco.cc/key-papers/paper-oba-cancer-immunol-immunother/), [Efficacy of adjuvant immunochemotherapy with polysaccharide K for patients with curatively resected colorectal cancer: a meta-analysis of centrally randomized controlled clinical trials](https://onco.cc/key-papers/paper-sakamoto-cancer-immunol-immunother/)

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