Mushroom extracts for cancer?

A recent question from a client about mushroom extracts for "immune modulation" in cancer patients led me to look into the evidence for these supplements. While the idea that mushrooms could contain medically effective compounds is reasonable, (there are many active chemical compounds, including some very toxic compounds) the evidence for their use is still weak. There have been traditional uses of mushrooms in cancer treatment for centuries or longer, and preliminary testing of mushrooms and compounds in mushrooms since at least the late 1970's. As is the case with many things which fall under the DSHEA as nutritional supplements, mushroom extracts are not required to be tested for efficacy or safety before being sold.

This website is the one my client was asking about. They claim that their two supplements, K9 Immunity and K9 Transfer Factor will help to modulate the immune system which will help to prevent cancer and also help the immune system to recognize the cancer and eliminate it if it is already present. They really have no data to support these claims, and so resort to vague, nonspecific claims of "immune modulation", "detoxification" and "support". One of the videos they have produced looks like a news feature, but is really the president of the company promoting the products. He is careful in that video to avoid specific claims, and says repeatedly that pet owners should pursue appropriate treatment, but their supplements can "improve quality of life". All of the testimonials indicate that the dogs that have done well received appropriate treatment for their cancer including surgery, radiation and/or chemotherapy.
There is never any evidence presented that using the supplements changed the outcome or course of therapy for any of these pets. A paper presented on the website as evidence of effectiveness is basically a series of uncontrolled, unblinded case reports with no controls for
comparison of outcomes, and does not really address the main claims of "immune modulation"
made by the site. Some of the dogs in the report died of their disease, some needed adjustments to their treatment due to side effects, (including immune suppression) and others had progression of their disease. Their definition of cancer as a failure of the immune system to recognize aberrant cells is very simplistic, and does not account for the complexities of cancer biology.

The website seems to be named to attract people searching for information about canine cancer, and has a discussion forum and pages giving basic information about four of the most common types of cancer in dogs, but every page and nearly every paragraph leads to a link or button to order their products. As with many unproven and untested products, the people who seem to be providing such sympathetic and valuable information are really just pushing their specific products. The cost of their two supplements would be between $240 and $300 per month for a giant breed dog (120lbs). That seems like a lot to spend for an unproven and probably ineffective treatment. If they are going to support research, they could at least do a randomized, controlled trail rather than a poorly done case series.