I would suggest waiting for WHO to publish their findings/study/recommendations on aspartame. From a brief look across a few reports it seems to be on a similar level to like, red meat levels of carcinogen.
However I am not a scientist so I cannot personally judge the veracity of these claims
What I meant is that an "increase by 30%" means nothing without first knowing your individual base risk. If you have, say, a 1% risk of getting a certain type of cancer at some point in your life and it increases by 30%, you now have a 1.3% risk. I don't know whether that's enough of an argument to deny yourself the pleasure of a soft drink you like.