Dementia and cancer ?

We all know someone with dementia - EODAT, AD, FTD, etc. - or we'd not be on here.

But NO ONE I know with dementia also has cancer.    How about you? 

Silly question , but why is it that people with dementia don't seem to get cancer as often ?

Put another way, does any one you know that has cancer ALSO have dementia? Probably not, right?

So, is this because cancers get replicating in humans who's immune systems are compromised, while people who's immune systems are superstrong resist cancer, but have a protein-folding proclivity caused by their own ( hyperactive?) immune systems?

So where are the professionals researching this question?

Remember Dr. Virginia Livingston-Wheeler's book titled "Conquest Of Cancer" ?  She discovered early-on that TB positive reactors seldom got cancer. She next presumed that TB stirred up those folks' immune systems,  and so abnormal cells, including many classified as cancers, got snuffed by white blood cells and killer T cells before they could become a replicating health hazard. Next she gave cancer patients TB, knowing she sould cure TB with anti-biotics. And finally, she began using cells from a patient's tumor or serum to grow anti-bodies specific to that type of cancer,  and inject those back into the patient.  So, read her book!  ( Just because some oncologists want to protect their turf by posting her on "Quackwatch" doesn't mean her methods should not be emulated, improved, expanded. )

Back to AD and other dementias - if spiking up one's immune system can help beat some cancers, would dampering it prevent some of the prion manufacturing, miss-folding and mal-absorption problems we call AD, ALS, PD, etc?