> Most healthy, active people who eat decently, get enough rest, and avoid drinking and smoking, will be able to eliminate cancer as it comes up
Incorrect.
There are tons of cancers that hide and mask with symptoms common to other symptoms. Kidney cancer, for example, presents pretty similarly to both kidney stones and UTIs. Even blood in the urine isn't proof positive that anything is wrong beyond either of those conditions. And, by the time blood is in the urine, it's often too late.
Liver cancer is even worse. The first symptoms you get can be thought of as a simple pulled muscle, just a little ache in the back. By the time you have appreciable problems, like turning yellow, it's quite advanced and too late to really do much.
There are common cancers like colon, skin, breast, and prostate that more fit your description of being mostly harmless so long as you get regular screenings and eat healthy. But, for every part of the body, a cancer can form and the symptoms are very often invisible.
I'm unfortunately all too familiar with how cancer looks. My wife currently has stage 4 cancer that started as kidney cancer. She does not drink or smoke, gets enough rest, and is very active.
What's a good way for an otherwise healthy person to screen for kidney cancer, in terms of trade-offs?
Annual MRI?
No I mean that people who are healthy in general are less likely (or completely unlikely) to “get cancer” in the first place because cancer is something that has more to do with an immune system failure, which happens due to unhealthy lifestyles or genetic problems in general which are unavoidable. Cancer only affects people who generally already have other problems (old, sick, unhealthy lifestyles etc.) and young people because they are growing very quickly.
Thus, in young people cancer presents rapidly as they develop, these screenings are expensive and unnecessary. For old/sick/unhealthy people, or people who are predisposed to certain cancers, they will probably get something else anyway, so its an expensive workup to help treat a disease that won’t actually benefit much in the long term.
I’m not against treating cancer, however let’s recognize that cancer treatment is already an expensive and resource/labor intensive process. And 10yr survival rates are not great for most cancers, we’re only slowing the burn, not stopping it. Sometimes you get lucky and die of something else before the cancer can come back, but nobody is ever “cured,” they are all just delaying the inevitable. Which, as we have seen, can sometimes be worth it (who wouldn’t want another 10 years with a loved one?), but that doesn’t mean our goal should be to find a way to “cure” cancer, it should be to find a way to better manage it, and these screenings don’t seem like they really are, or at least the use-cases for them are minimal.