New paper below .
I suppose that many stopped taking vitamin E following publication of the SELECT [Selenium and Vitamin E Cancer Prevention Trial] study - a study that I regard as an expensive fiasco. If someone who stopped had been taking alpha tocopherol, then stopping was probably a good thing.
"gamma-tocopherol (γ-tocopherol) is the most common form found in the North American diet" - not alpha tocopherol, which tends to be dominant in the blood. 
What is not generally understood is the competition for transport among the 8 isoforms of vitamin E. Supplementation with one will tend to drive down levels of the others.
Gamma tocopherol is the most active of the tocopherols against PCa, & gamma tocotrienol appears to be even more active.
I take DeltaGold which has only delta & gamma tocotrienols. (The former has cardiovascular benefits, which might be significant for PCa patients who tend to have greater CVD risk.)
From the new paper :
"The disappointing results from large clinical studies of α-tocopherol (αT), the major form of vitamin E in tissues, for prevention of chronic diseases including cancer have cast doubt on not only αT but also other forms of vitamin E regarding their role in preventing carcinogenesis. However, basic research has shown that specific forms of vitamin E such as γ-tocopherol (γT), δ-tocopherol (δT), γ-tocotrienol (γTE) and δ-tocotrienol (δTE) can inhibit the growth and induce death of many types of cancer cells, and are capable of suppressing cancer development in preclinical cancer models. For these activities, these vitamin E forms are much stronger than αT. Further, recent research revealed novel anti-inflammatory and anticancer effects of vitamin E metabolites including 13'-carboxychromanols. This review focuses on anti-proliferation and induction of death in cancer cells by vitamin E forms and metabolites, and discuss mechanisms underlying these anticancer activities. The existing in vitro and in vivo evidence indicates that γT, δT, tocotrienols and 13'-carboxychromanols have anti-cancer activities via modulating key signaling or mediators that regulate cell death and tumor progression, such as eicosanoids, NF-κB, STAT3, PI3K, and sphingolipid metabolism. These results provide useful scientific rationales and mechanistic understanding for further translation of basic discoveries to the clinic with respect to potential use of these vitamin E forms and metabolites for cancer prevention and therapy."