Hello, and thank you for posting. 

As with all treatments the benefits of having chemotherapy needs to outweigh the risks, and nobody is going to know that for your brother better than his hospital team. The team will have discussed your brother's case at an MDT (Multi Disciplinary Team meeting) where several specialists will take into account your brother's current situation and over all general heath and they will work out what they feel in their opinion is the best course of action. Of course people can have side effects from treatment but it is not easily predicted how each person will be, but the support of the chemotherapy teams and additional medications to manage side affects will help.

If your brother is concerned it is important he talks this through with his team. Or if you are attending an appointment with him, you may have some questions you would like to go through with his Doctor. 

I've placed a couple of links that maybe useful. This first one is about living with advanced bowel cancer.

This second one talks specifically about diabetes and chemotherapy.

Take care, and if there is anything else you would like to talk through, maybe chat with one of the nurses on our helpline.  The number to call is Freephone 0808 800 4040 and the lines are open from 9am till 5pm Monday to Friday.

Sarah.