abdominal pains??

Hi guys, quick recap, dad diagnosed in july 04, stage 3, 5 positive nodes, clean ever since, but for the past couple of weeks now he's been getting abdominal pains/cramping??? I'm obviously worried, he has an appointment with the oncologist next Tuesday to see what's going on. He just had a scan about 7 weeks ago and all clean but i know cancer can come back pretty quick. The only other thing is that he claims the discomfort goes away at night when he's in bed??? I'm thoroughly confused?? Any input guys? I am so scared and nervous right now. I hope it's only gas or something.