Sure, humans under 40 are also very resistant to cancer. My point was that cancer comes with old age, and aging seems to be a way for us to die before cancer or dementia kill us. There are "weak" evidence that people who have dementia are less likely to get a cancer. I understand that some mammals like whales or elephant seems to be very resistant to cancer, but if we were to double or triple their average life expectancy, other disease may become more prevalent, maybe even cancer.