This post will be followed by a number of fungus-specific posts.
Medicinal mushrooms are those that have been found to have an immunomodulatory effect in the body. There is generally a long history of human medicinal use, albeit in societies where PCa has been rare. i.e. there is no "traditional" fungi PCa treatment.
The active agents in the fungi are generally considered to be the beta glucans , although the triterpenoids  are also valued.
The casual purchaser of mushroom products will likely be wasting his money, & there is no guarantee that an expensive product will deliver the goods. The best products will boast of their processing methods & will specify active ingredients in terms of standardized amounts.
Paul Stamets is highly respected in the fungi subculture. He founded Fungi Perfecti. It has a very wide range of expensive products. Take a look at the blurb for "Fungi Perfecti, Host Defense, MyCommunity, 120 Veggie Caps" , list price $69.95, & see if you think it is anything but mushroom powder.
Creating a powder will certainly damage fungi cells, but most will remain intact. The walls of the cells consist of chitin ("Ky-tin") (as comprising shrimp shells) . The cells do not readily give up their contents.
Extraction is complicated. A hot water process will liberate the beta glucans, whereas alcohol is needed to release the triterpenes.
Look for double extraction in products.
One company that claims to use double extraction for all of their products is Oriveda . It is based in Holland. It is frustrating to have to buy from abroad & fret about whether U.S. Customs will inspect the shipment, but that is what I have done for their turkey tail.
"Biomass" versus "Fruiting Bodies". Biomass may be good enough for beta glucans but fruiting bodies are the source of the triterpenoids.
Can I do this at home?
Seems that it may be feasible. Dried mushrooms would have to be ground to a powder & steeped in 100-proof vodka, say, for quite a long time (? days). A fine filter to separate the alcohol extract from the grounds. The grounds would be simmered in water for 5 hours or so & filtered. The water extract would then be added to the alcohol extract. Do your own research though on optimum methods. I have never tried it.