My husband drinks 35 cans of sugar free Coke a week, what are the health risks?

It is the calorie and sugar free coke, but what are the risks of consuming that much artificial sweetener over a long period of time (years)? He is about to turn 34 this week, male, five foot eight inches and about 270-300 pounds. No medications other than some generic Viagra he orders online for ED but only uses about once every two-three months due to his low libido, does not smoke or drink other than 2-3 shots a year and no recreational drugs. I am extremely worried if those chemicals can lead to cancer especially at such high doses