As PTC (or PROP, more regularly used due to lower toxicity) bitterness negatively associates in several studies with vegetable intake, and in particular cruciferous vegetables which should offer some benefits to cancer prevention, it would be reasonable to hypothesize that people sensitive to this kind of bitterness would be more vulnerable to for example colon cancer. Basson et al tested this in 2005, and found PROP bitterness correlated with polyp counts, a key predictor of colon cancer risk. As people experiencing more bitterness from PROP are supposedly skinnier, this relationship must be quite complex. 

http://link.springer.com/article/10.1007/s10620-005-2462-7