Cancer: You have genes in your body that essentially determine whether you get cancer: HER and BRAC genes are a couple examples.
The more factors you expose yourself too i.e. UV rays, smoking, nitrites, and other chemicals introduced to your system through daily activities can increase the chance of those genes getting mutated. If one of them gets mutated then you'll end up with a benign tumor, which is ordinarily harmless and it can be removed. If BOTH get mutated then it will result in a malignancy in which you have cancer.
So, cancer in general comes down to chance. If you're lucky both your genes won't mutate.
Furthermore, vaping on a low temperature scale should do little damage to the lungs especially if you let the vapor cool in a bag system as far as physical damage. Regarding carcinogens in this case, a high-tech vape used properly should reduce the amount of toxins into your system significantly. Suppose <1% of carcinogens enter your body from vaping as opposed to smoking, you still have a "risk" for cancer although it would probably be less than eating a plate of nitrites. If you're vaping and worried about malignancy, I'd focus more on other daily activities... If, hypothetically, you happened to get cancer from vaping and that <1% was the ONLY source of carcinogenic agents you exposed yourself too...that's just misfortune at its prime.