The term adjuvant means to add to the primary therapy to help or modify it.

Like riding a bike: To get from point A to B, you need wheels, pedals and steering. To get to point B more efficiently you might add gears. By themselves, the gears will get you nowhere but added to the pedals, wheels and steering it will make your journey a whole lot more effective.

The study quoted by Paul was done at a time when the researchers were trying to figure out if there was a place for chemo. The study indirectly compared survival figures between those who had either surgery or radiation VS the people who had radiation or surgery plus chemo. Sound familiar?

Since that study was done, the researchers have indeed found a place for adjuvant chemo which is during radiation not after it.