New study below [1].
First, it is unfortunately necessary to address the harmful fallout from vitamin E intervention studies that used only alpha tocoperol.
Vitamin E comprises 8 isoforms: 4 tocopherols & 4 tocotrienols (alpha, beta, gamma & delta, in each case). Alpha tocopherol is the isoform commonly predominant in the blood, so the assumption is that this is the most valuable. No consideration that the most valuable components might be quickly depleted.
PCa studies have reported that the gamma forms of vitamin E are most beneficial, with gamma tocotrienol being more valuable than gamma tocopherol.
Note that the 8 isoforms are never all found together in nature. Supplements that contain a little of everything may seem to offer the greatest protection, but this is not so.
The problem is that the isoforms compete for transport. The presence of one isoform will affect the uptake of the others. Adding an alpha tocopherol supplement will drive down all other isoforms. Profoundly stupid.
Clinical trials that used pure alpha tocopherol actually put the intervention cohort at a disadvantage. (Unless, of course, the men started with a deficiency.)
The Physicians’ Health Study II (2009) [2] used "400 IU synthetic α-tocopherol or its placebo on alternate days". Why synthetic?
"During a mean follow-up of 8.0 years, there were 1,008 confirmed incident cases of prostate cancer and 1,943 total cancers. Compared with placebo, vitamin E had no effect on the incidence of prostate cancer."
A 2014 follow-up [3] did not alter the conclusion that vitamin E was not PCa-protective.
The abysmal SELECT (Selenium and Vitamin E Cancer Prevention Trial) study (2009) [4] used "400 IU/day of all rac-α-tocopheryl acetate" - another synthetic alpha tocopherol.
"There were nonsignificant increased risks of prostate cancer in the vitamin E arm"
From a 2011 follow-up paper [5]: "Dietary supplementation with Vitamin E significantly increases the risk of prostate cancer among healthy men."
That pretty much killed interest in vitamin E for many men.
In a 2000 Hopkins study [6]:
"For gamma-tocopherol, men in the highest fifth of the distribution had a fivefold reduction in the risk of developing prostate cancer than men in the lowest fifth ..."
"The use of combined alpha- and gamma- tocopherol supplements should be considered in upcoming prostate cancer prevention trials ..."
The authors seem unaware of the transport competition issue. If you want more gamma-tocopherol, skip the alpha-tocopherol.
There is no comparable study for tocotrienols, but I believe that gamma-tocotrienol is a better bet.
DeltaGold tocotrienols derived from annatto is roughly 10% gamma & 90% delta. At first glance, this does not appear to be ideal. However, other options are even worse. The attraction is that delta tocotienol is strongly associated with cardiovascular health - which is a particular concern for men with PCa. & the product has no tocopherols at all. [7]
The new Japanese study looked at delta tocotrienol:
"A hallmark of the progression of prostate cancer to advanced disease is the acquisition of androgen-independent growth. This malignant phenotype is characterized by resistance to conventional treatments and predisposes to formation of hypoxic regions containing stem-like cancer cells. Unfortunately, an effective therapy to target prostate cancer stem cells under hypoxia has not yet been established. In this report, we studied whether δ-tocotrienol (T3), a vitamin E family member that has exhibited the most potent anti-cancer activity, could suppress the survival of prostate cancer stem-like cells."
"δ-T3 demonstrated a cytotoxic effect on prostate cancer stem-like cells in a dose dependent manner and a reduction in the protein levels of hypoxia-inducible factor (HIF)-1α and HIF-2α."
"Overall, these results suggest that δ-T3 could inhibit the survival of prostate cancer stem-like cells under hypoxia, primarily through the inactivation of HIF-1α signaling."
A lot of brands carry DeltaGold, e.g. [8].
-Patrick
[1] ncbi.nlm.nih.gov/pubmed/294...
[2] ncbi.nlm.nih.gov/pmc/articl...
[3] ncbi.nlm.nih.gov/pmc/articl...
[4] ncbi.nlm.nih.gov/pmc/articl...
[5] ncbi.nlm.nih.gov/pmc/articl...
[6] ncbi.nlm.nih.gov/pubmed/111...
Vitamin D and PCa mortality risk. 
Boron Inhibits Tumor-induced Angiogenesis
Food supplements I hope will help
Yet another major study proves no causal connection between Vitamin D and prostate cancer
