This is not a moral dilemma, in my opinion. Because the answer is obviously yes, since trying to modify the teleported being during the teleport risks causing more issues beyond the cancer.

On the other hand, if the medical knowledge evolves enough to make such "fix" possible, then it would probably be available in another way. Or at least, the healing teleport would be offered as a specialized kind of surgery, only applied in hospitals (if they still exist).