The general thinking is not that the cancer will hopefully stay dormant but there's a chance it will flare up in the future. The act of flaring up is what makes the tumor a malignant cancer as opposed to a benign cyst. A cancer cell is already flaring up by definition.
Rather, the usual model is that you physically extract the cancer, or you poison it, and you hope that you removed or killed all of the living cancer cells. If one is left, the cancer will grow back over time. This is why a metastatic cancer is so much worse than one that hasn't yet metastasized - after metastasis, cancer cells can be located pretty much anywhere in your body, but before metastasis, they are all localized to wherever the cancer originally developed, and if you remove enough tissue, it's plausible that you might get them all.
This model is somewhat in tension with (part of) the concept of partial remission, where the growth of a cancer becomes slower. But in such a case, it is even more obvious than usual that the cancer of the future is the same cancer as the cancer of the past, since we could observe it the whole time.
You might also consider the implications of the fact that the terminology for what appears to be a total absence of cancer is "cancer in remission". We say that because we can't know whether the cancer is actually gone. If it isn't gone, it will come back.
Rather, the usual model is that you physically extract the cancer, or you poison it, and you hope that you removed or killed all of the living cancer cells. If one is left, the cancer will grow back over time. This is why a metastatic cancer is so much worse than one that hasn't yet metastasized - after metastasis, cancer cells can be located pretty much anywhere in your body, but before metastasis, they are all localized to wherever the cancer originally developed, and if you remove enough tissue, it's plausible that you might get them all.
This model is somewhat in tension with (part of) the concept of partial remission, where the growth of a cancer becomes slower. But in such a case, it is even more obvious than usual that the cancer of the future is the same cancer as the cancer of the past, since we could observe it the whole time.
You might also consider the implications of the fact that the terminology for what appears to be a total absence of cancer is "cancer in remission". We say that because we can't know whether the cancer is actually gone. If it isn't gone, it will come back.