Depends, colon cancer, breast cancer, prostrate cancer, etc. are pretty commonly tested/screened for in certain age groups and that definitely saves lives.
My aunt died of pancreatic cancer last year. It's a pretty common and aggressive form of cancer. She only had a few months from diagnosis to the grave. By the time she got diagnosed, there was nothing that they could do except provide pain relief.
My dad got lucky to get his detected relatively early (they happened to be doing an unrelated test and "saw something", but that just meant two years of chemo and all those side effects before he died. If they hadn't found it when they did it would have been 1 year of side effect free life followed by 6 months of pain for something untreatable - in short overall a better end of life though he would have lost 6 months. If they had found it 6 months sooner though odds are it would have been treated and he would still be with us.
If we don't detect more people early and try to cure them, it will never be solved. The more people that get detected early, the better chance everyone has of surviving, especially those in the future.
My aunt died of pancreatic cancer last year. It's a pretty common and aggressive form of cancer. She only had a few months from diagnosis to the grave. By the time she got diagnosed, there was nothing that they could do except provide pain relief.