Among professionals, jargon like "survival" can be useful; it is generally used correctly, among others who will interpret it correctly. And yes, we can learn from studies where these terms are in play. We can certainly compare treatments among groups of early-treatment patients and see if one regimen is better than another, using five-year survival as a context. We can also compare late-treatment patients to early-treatment patients who have arrived at the same late stage, and see if early treatment has provided an edge in survival from that point forward.
But the idea that early treatment inevitably causes a patient to live longer is not always proven. Treatments make tumours stop growing, or shrink, or even go away. This is not the same as saying that the patients die significantly later than they otherwise would. We want to believe this, and there are people and corporations with an interest in encouraging us to believe it, but it is, as I said, very tricky to prove in some cases.
Now, here is a discouraging observation: there certainly are occasional breakthrough treatments, but generally, when we compare different regimens, we rarely see a dramatic difference in effectiveness among study groups, which suggests that the treatments probably aren't doing as much as we've been led to believe. Especially in the difficult cases.
Let's consider a few of the really tough cancers: stomach, pancreatic, lung, ovarian: these have very poor survival rates and treatment is usually not very effective. Why? Because symptoms rarely show until the disease is well advanced and metastatic. Catching one of these cancers early is usually a matter of luck.
Generally, there is little luck to speak of when you are diagnosed with one of these cancers. Your oncologist sits you down and gives you "the talk". It's advanced and spreading; we're going to do all we can; there are treatments and we will explore all the options; we learn more every day about treating this disease, etc. But you know that with a late diagnosis, there won't be a great deal of time before you die, and you think, my God, if only it could have been caught earlier: I would be able to live longer. You've heard all the glowing rhetoric about early diagnosis and early treatment, and you feel cheated of your chance to really fight the disease, and cheated of the most valuable thing of all: time to live.
But this might be total nonsense, and you might be suffering additional anguish for no reason. You see, with a late diagnosis, your survival is going to be short, but your life might not be much shorter than it would be if you'd been diagnosed early. As we discussed previously, you might already have survived quite a long time with your cancer; you simply haven't been aware of it. There is no reason to believe that you are not already an impressive cancer survivor.
Unfortunately, few patients will feel this way, and this is an incredibly cruel consequence of the survival propaganda that the media and medical industry disseminate.