Hi Marie,
Congratulations to your Mom in being one of the lucky few able to have Whipple surgery and the possibility of a cure. I'm sure that the oncologist has told your Mom that radiation and chemo often go together and one is a booster for the other. Radiation is the standard of care for treatment after Whipple surgery in the United States. This cancer is so insidious that your Mom really ought to do all she can to prevent a recurrence. The reason behind doing adjuvant radiation and chemo is to kill any stray cells that might not have been gotten during surgery or any micro-metastases that were too small to be seen. There are many kinds of medications that are available to help offset the side effects of the radiation and chemo. Some people never have much trouble with either one; my husband didn't have much trouble, and he was 76 years old when he had treatment. He is still alive today.
She would be wise to give herself all the protection that is available. Good luck and Godspeed.
Joan L