Interest in Cordyceps militaris for PCa is recent (only 4 studies) & mostly Korean. No PCa studies for Cordyceps sinensis as yet.
Not much to be gleaned from Wikipedia about Cordyceps militaris - nice picture though .
Summary:- Studies are interesting, but involve only two labs & no animal studies.
 (2010 - Taiwan)
"The purpose of this study is to isolate the pure compounds from the extracts of Cordyceps militaris obtained ... and evaluate their anti-inflammatory and anticancer properties."
"... compounds 3 and 8 were potent anti-proliferative agents with an IC(50) value of 35.6 and 32.6 microg/ml toward PC-3" cells
"The compounds 1 and 2 showed potent anti-proliferation in PC-3 ... cells"
Alas, not very informative. But does indicate that a basic extract might have value.
 (Korea) Cordycepin appears to be the major bioactive compound under study.
"Cordycepin (3'-deoxyadenosine), a major bioactive compound of Cordyceps militaris, has many pharmacological actions, such as anti-inflammatory and anticancer activities. In this study, the relationship between inhibition of cell motility and anti-invasive activity by cordycepin in LNCaP human prostate carcinoma cells was investigated."
"Within the concentration range that was not cytotoxic, cordycepin time-dependently inhibited cell motility and invasiveness of LNCaP cells."
"... cordycepin inhibited the expression and activity of matrix metalloproteinase (MMP)-2 and MMP-9, and simultaneously increased levels of tissue inhibitor of metalloproteinase (TIMP)-1 and TIMP-2."
The MMP family, particularly MMP-2 & MMP-9, break down the matrix that holds cells in place. Inhibition of MMPs is a big deal, even if the dose is not cytotoxic.
[3b] (2013 - Korea)
"Cordycepin is the main functional component of Cordyceps militaris, which has been widely used in oriental traditional medicine. This compound has been shown to possess many pharmacological properties, such as enhancing the body's immune function, and anti-inflammatory, anti-aging and anticancer effects. In the present study, we investigated the apoptotic effects of cordycepin in human prostate carcinoma cells."
"We found that treatment with cordycepin significantly inhibited cell growth by inducing apoptosis in PC-3 cells."
"The cordycepin-induced apoptosis was also associated with the generation of intracellular reactive oxygen species (ROS). However, the quenching of ROS generation with antioxidant N-acetyl-L-cysteine conferred significant protection against cordycepin-elicited ROS generation, disruption of the MMP, modulation of Bcl-2 and IAP family proteins, caspase-3 and -9 activation and apoptosis. This indicates that the cellular ROS generation plays a pivotal role in the initiation of cordycepin-triggered apoptotic death."
Once again, a reminder not to use NAC when taking anything that acts via ROS. Invariably, apoptosis requires ROS.
"Cordycepin, an active ingredient of the insect fungus Cordyceps spp., shows strong antioxidant and anticancer activities. Several molecular mechanisms have been attributed to its inhibitory effects on a wide range of tumor cells; however, the mechanism causing cancer cell death is still obscure. For the current study, we further investigated the mechanism responsible for targeting cordycepin-induced cell death and its association with autophagy in human prostate carcinoma LNCaP cells. Our results show that cordycepin resulted in significant reduction in LNCaP cell survival by inducing apoptotic cell death. Cordycepin treatment caused a dose-dependent increase of pro-apoptotic Bax and decrease of anti-apoptotic Bcl-2, triggering collapse of the mitochondrial membrane potential and activation of caspase-9 and -3. "