The first link contains the info I know about a possible cause and types of cancer. Ask your doctor as how it may effect you. The next contains a section on toxicity and dosage of tocotrienol. My wife experienced no side effects. She used the Now brand red palm tocotrienol. The oncologist approved it's used but did not recommend it. I think it took about nine to twelve months. There was no effort to push. She is a small person and the dosage was adequate. Always consult your health care professional before using any supplement. The third link is about thiamine and discusses fat soluble forms that are able to pass through the blood/brain barrier more effectively than water soluble forms. The last link is a followup on thiamine's role in an unexpected area.
https://www.mskcc.org/cancer-care/patient-education/hydroxyurea-01
https://nutritionandmetabolism.biomedcentral.com/articles/10.1186/1743-7075-11-52
https://nootropicsexpert.com/vitamin-b1-thiamine/
https://www.eonutrition.co.uk/post/thiamine-deficiency-a-major-cause-of-sibo