IHS.
Im very sorry to hear of your sisters woes.
Breast cancer is notorious for often recurring after the initial tumour is felt to have been dealt with.
Its not uncommon for even a 'thorough exam' to not pick up signs of very early recurrence as it only takes a cell or 2 to have metastasized and to lodge somewhere waiting to grow once more-our fancy imaging techniques are not up to the job of detecting something so small.
You are right to have concerns regarding possible interactions with her prescribed meds but there are other factors to consider:
If she has recurrent disease affecting the brain, it is also possible that she may have recurrent disease in the lungs, bones, liver and bone marrow.She is going to need an isotope bone scan and full body MR/CT to detect disease in the liver/lungs or indeed elsewhere.
The issue of recurrent disease in the bones and liver is particularly important as this can have a bearing on whether or not taking DMT is advisable.Liver involvement can alter the metabolism of certain meds which can have knock-on effects on the action of other substances both endogenous and exogenous.
Deposits in the bones can cause a high blood calcium which can affect mental functioning amongst other effects.
The presence of disease in your sisters brain can cause the pituitary gland to release vasopressin inappropriately causing the blood sodium levels to fall to a level through dilution which can also alter mentation and increase the risk of fits.
There really are many factors consider, and each of these can affect others.
May I ask-what meds is she on?
Sincerely, I wish you and your family well in what is going to undoubtedly be a most difficult time.
I am paranoid of my brain. It thinks all the time, even when I'm asleep. My thoughts assail me. Murderous lechers they are. Thought is the assassin of thought. Like a man stabbing himself with one hand while the other hand tries to stop the blade. Like an explosion that destroys the detonator. I am paranoid of my brain. It makes me unsettled and ill at ease. Makes me chase my tail, freezes my eyes and shuts me down. Watches me. Eats my head. It destroys me.