I have been talking to a variety of doctors recently about a kidney cancer co-morbidity (loss of balance and a slow growing brain tumor called a meningioma)

Nerosurgeons have suggested various forms of radiation (proton and photon), and a neurologist suggested B12.  The B12 didn't help.

So at the advice of a friend, Bruce Iiams, I've recently started talking to Dr. Berlanger, a naturopath.  First thing he noted was that the form of B12 I've been taking (cyanocobalamin) is not as readily absorbed as methylcobalamin.  He also suggested a series of tests, including several targeted genetic (DNA) tests after seeing elevation of some blood chemicals.  And lo and behold: a Labcorp test showed that I have a MTHFR variant: C677T.

This variant is associated with decreased MTHFR activity and increased homocysteine levels in the blood, which may increase the risk of premature cardiovascular disease (CVD), formation of inappropriate blood clots (thrombosis), and stroke. (see hyperhomocysteinemia) Note also that in my 20180520 hackathon, HelloKidney2 noted this as a kidney cancer marker of interest based on this 2007 paper.

Well, I guess I have an answer. Hooray. Next step: Eat more vegetables and try more B vitamins (B6, B9(?), B12).