Can anyone help please? Is there any case law for the actual treatment of cancer?

I am going to appeal very soon with a client who has Hodgkins disease,and the intense treatment is really knocking him about, severe fatigue,nausea,night sweats and he is not able to prepare and cook a main meal and change his bed. He has to rest 18hours a day, and 10-11 days/ a fortnight are bad for him. No DS1500 has been issued, and he has just started a 2nd 6 month course of chemo,his first course started Feb.

You don't say whether chemo- or radio-therapy, and I couldn't find anything as specific as you're looking for. However, try
http://www.osscsc.gov.uk/aspx/view.aspx?id=265, which should enable you to access CDLA/4134/2001, which I'm currently using in a reconsideration request. Although the CD's about dialysis, I've argued that the chemotherapy is similar because of the way the chemotherapy is delivered, by PICC. I summarised with this:

'I believe that the case has some similarities with Commissioner’s Case CDLA/4134/2001, insomuch as the PICC is similar to the dialysis mentioned in that decision, with similar restrictions due to the nature of the catheter insertion and the results of the chemotherapy being as draining and tiring as dialysis.'

Hope it's of use.