But: High glucose levels do not cause diabetes. Diabetes causes high glucose levels. Once they go up you need treatment as you either have no insulin or are producing not enough and need to mediate that. Both are diabetes.
Ding ding ding. My wife's blood glucose levels went from normal 90's range to averaging around 120 over the summer to averaging close to 200 last December. Her liver had a heavy disease burden, and my understanding based on my own research (because none of her doctors would address it) is that this can affect insulin sensitivity, which in turn can cause elevated blood sugar. This does not seem to be a dominant effect, however, and can go the other way as well.
When it does create hyperglycemia though, it also creates an unfortunate feedback loop in that the elevated blood sugar levels can increase the cancer progression, compounding the effect.
But guess what, nobody will bite. I had to go to some weird third party service to get a prescription and spend weeks going back and forth with oncology and endocrinology to get anyone to comment on it. Oncology said NFW with zero rationale and endo said a small starter dose with regular monitoring for lactic acidosis due to compromised liver function.
Today everyone, even doctors, knows that high blood sugar levels increase the odds of cancer AND diabetes. That's why everyone and his dog is taking metformin and why that drug is almost always the first ingredient included in "life extension" cocktail drug tests.