Posh, I am so sorry for your mum and dad, and it is very hard for you too.
Please remember that there are over 200 different types of cancer, and that treatments vary considerably depending on where the cancer is, how big and what stage/grade.
For many people, the treatments are not pleasant but nothing like as severe as for your mum. I had cancer and had major surgery and was offered radiotherapy, but after a great deal of thought declined it.
These days, medical professionals dealing with cancer work very hard to make sure patients and their families understand the treatment options on offer and are making decisions based on what they feel comfortable with.
Six years on I am still here. Sadly, a dear and very close friend currently has terminal bowel cancer and I've been with her through it. When she was having chemo, I often used to take her to appts and we'd chat to the other patients. One of the other guys having the same treatment as her was still in work as he felt well enough, and not all treatments these days make you lose your hair.
For anyone who is reading this and is scared, please don't be. There is lots of help and support available.
OP, have you thought of setting up a rota for taking your mum to hospital to give your dad a break? Many charities will help and often friends will be happy to. When I was going to the hospice as a day patient they had some wonderful volunteer drivers who helped transport me - I was so grateful.
Does your mum have a specialist nurse she and your dad could talk to about getting extra help? Macmillan are very good too.
It's not easy watching someone you love go through this. All you can do is everything possible to make the practicalities as easy as possible for your mum and dad, and be strong for them.
Here's hoping for a positive outcome.