Hi Louis and welcome to the forum. Fatigue is something a lot of people with cancer will be aware of and affected my husband a great deal. His consultant explained that it was partly due to the cancer's affect on the body and also the medication helped to treat/control it.  It frustrated my husband a great deal but he and we had no control of the amount of time he either slept or had no energy to do anything much. He just had to rest when his body raected in this way.

  Both this and any pain your granddad is experiencing should be mentioned to his medical team and or GP. I am not sure there is much they can offer for the fatigue but there are many many medications that can help with pain relief if they are aware of the problem (my husband took a lot of persuading to up his levels of pain relief thinking he could 'manage it'). If he has an allocated nurse then he could talk to them about pain management.  Do hope the treatment will be helpful and his doctors can make him feel more comfortable.  Regards  Jules54