Davidcpa:

My understanding is as follows. Some cancer cells are more robust than others. Chemo will kill the weaker cancer cells but its not powerful enough to kill the more robust cancer cells. Consequently, chemo alone is not a "definitive" treatment for the disease.

However, chemo alone (in the form of Induction Chemo) is a useful adjunct to more "definitive" treatments (like concurrent chemoradiation). As you point out, chemo is not "targeted" to any one location, so if a few cancer cells have metasticized to some distant part of the body, the chemo will reach (and hopefully kill) these cells. This reduces the chance that the cancer will recur at some location distant from the original/primary site (thereby improving your chances of long-term survival).

Once they've used Induction Chemo to "mop up" the few (undetectable) cancer cells that have escaped to distant locations, they can use concurrent chemoradiation treatment (CRT) to attack the original/primary site in a targeted manner.

One thing about Induction Chemo: after its killed the weaker cells, only the stronger (more robust) variety of cancer cells will remain. Without further treatment, these will start growing again and they won't be competing with the weaker cancer cells for resources. So if you wait too long after Induction Chemo to begin your "definitive" CRT, your cancer will be as big as it was to start with and - even worse - it will be composed entirely of those stronger (more robust) cancer cells. So give yourself a SHORT time (e.g., 2 weeks) to recover from the Induction Chemo and then jump right into the CRT.

Hope that helps, Rob