Single agent polysaccharopeptide delays metastases and improves survival in naturally occurring hemangiosarcoma

Brown, D. C., & Reetz, J. (2012). Single agent polysaccharopeptide delays metastases and improves survival in naturally occurring hemangiosarcoma. Evidence-Based Complementary and Alternative Medicine, 2012, 384301. https://doi.org/10.1155/2012/384301

What This Paper Covers: Turkey Tail Mushrooms for Canine Hemangiosarcoma

The authors asked whether a single oral product derived from Coriolus versicolor (turkey tail, “Yun Zhi”) could slow metastatic spread and extend survival in a naturally occurring, fast-moving canine cancer model. Fifteen client-owned dogs were randomized to three daily PSP doses (25, 50, 100 mg/kg), followed monthly with contrast-enhanced harmonic abdominal ultrasound and thoracic imaging until death, with necropsy confirmation. Safety was tracked with serial complete blood counts and chemistry panels.

Background on Splenic Hemangiosarcoma (From the Authors)

Hemangiosarcoma is a malignant tumor of vascular origin, most often arising in the spleen of middle-aged to older dogs. It spreads rapidly through blood or by implantation after a splenic rupture, and surgery alone carries a poor outlook: median survival about 19–86 days, with fewer than 10% alive at 12 months.

Doxorubicin-based chemotherapy improves medians to roughly 141–179 days, but it is costly, time-intensive, and rarely changes one-year survival, so many families do not pursue it.

The authors also note that about 70% of dogs with non-traumatic hemoabdomen and a splenic mass have hemangiosarcoma, and fatal hemorrhagic crises within months are common due to metastases to the liver, omentum, or mesentery.

What PSP Is (As Used Here)

PSP is a protein-bound polysaccharide extracted from Coriolus versicolor. In this study the product was I’m-Yunity PSP, isolated from the cov-1 strain’s mycelium and manufactured under GMP controls.

The authors emphasize that “PSP” is a general term and different brands can vary in polysaccharide and peptide composition, which is why naming the product matters when interpreting outcomes. They summarize prior lab work showing PSP can modulate immune parameters and shift cancer cells toward growth arrest and apoptosis, and they reference earlier animal studies with antitumor signals.

Study Design

This trial enrolled pet dogs whose spleens were removed for splenic hemangiosarcoma. A pathologist confirmed each diagnosis. Owners who declined chemotherapy allowed the researchers to test the mushroom extract on its own.

Dogs were randomly assigned to one of three daily oral doses of I’m-Yunity polysaccharopeptide: 25, 50, or 100 mg/kg. To keep the groups balanced, randomization accounted for whether metastases were already visible at the start. Both owners and investigators were blinded to which dose each dog received.

Monthly checkups included imaging by a board-certified radiologist. Each scan was compared with the dog’s baseline to see when metastasis first appeared or worsened. Survival was tracked from surgery until death.

For the statistics, the authors used a method called Kaplan–Meier survival analysis. This is a way of showing, over time, how many dogs in each group were still alive or still free of metastasis. It helps compare survival between groups, even if not all dogs died at the same time.

Key Findings

• Time to documented abdominal metastasis was longer at 100 mg/kg/day (median 112 days) than at 25 mg/kg/day (median 30 days), a significant difference. The 50 mg/kg/day group had 35 days and did not differ significantly from the others.
• Median survival was 199 days at 100 mg/kg/day, 117 days at 50 mg/kg/day, and 86 days at 25 mg/kg/day. The 199-day median exceeded published medians for doxorubicin protocols cited by the authors, although survival curves among doses were not statistically different in this small cohort.
• Serial hematology and chemistry remained within expected ranges across groups, and no adverse effects were attributed to PSP.

What the Authors Are Communicating

The dose pattern suggests a single oral product, I’m-Yunity PSP, can delay metastatic progression in a real-world canine population that did not receive chemotherapy, with an associated extension of median survival and good tolerance.

The authors position naturally occurring canine cancers as efficient translational models that can justify larger, placebo-controlled trials and help clarify where a standardized PSP fits relative to, or in combination with, standard chemotherapy.

Mechanisms the Authors Highlight

Drawing on prior work, the paper frames PSP as both an immunomodulator and a direct antitumor agent. Reported actions include increased leukocyte and immunoglobulin measures in human studies, and, in cell and rodent models, cell-cycle restriction at the G1/S checkpoint, altered expression of apoptotic regulators, and reduced proliferation, with little inhibitory effect on normal cells. These mechanistic signals help explain why an antimetastatic effect might be seen clinically.

Practical Dose Guidance From This Study

The only doses tested were 25, 50, and 100 mg/kg/day of I’m-Yunity PSP. Within this trial, the strongest signal for delaying metastasis and the longest median survival were observed at 100 mg/kg/day. Because “PSP” products differ in composition, the authors caution against assuming that dose applies to other brands or extracts; any clinical use should be supervised by a veterinarian familiar with product quality and monitoring.

Limitations and Next Steps

This was a small, single-center, dose-comparison pilot without a placebo arm, funded by the product’s manufacturer, and the survival curves across doses did not reach statistical separation. The authors call for larger, longer, multi-site, placebo-controlled studies that also compare, or combine, PSP with standard chemotherapy to define best use.

Plain-Language Summary

Turkey tail (Yun Zhi) is a mushroom. Its extract, called PSP, was given daily as I’m-Yunity capsules to dogs after spleen removal for a fast-spreading cancer. In this small study the highest dose group took longer to show cancer spread and lived longer on average, and routine bloodwork stayed stable. This is encouraging for families who are not using chemotherapy, and it supports doing larger studies to confirm who benefits most and how PSP should be used in practice.