Make sure your doctors KNOW that you are still smoking. You will have an increased risk of developing pnemonia or other lung infections during chemo (on top of the risk that chemo already gives, and especially if your white blood counts drop too low) as well as other infection. You will also recover slower than you would if you werent smoking.
I dont know about the interaction of the chemicals themselves with the chemo though. The stuff I said is more on a biological level.
Your body has shown an aptitude for making cancer out of normal cells. Why would you deliberately suck carcinogens into your lungs while in treatment for cancer?
Geez, just quit. Don't buy into the PR about how impossible it is to quit. Just freakin do it.