Mum just diagnosed with lung cancer

My 74 year old mum originally went to the doctors feeling dizzy and then had a chest x-ray which showed a shadow on her lung.  After many tests over two weeks, last Friday we sat in front of the consultant who said the words that mum had cancer.  Mum has smoked for 60 years and for her it did not come as a surprise, for me it was devasting.  Even worse when the consultant said it had spread up her chest to the other side, therefore was incurable.  We now have to wait for an appointment with an oncologist to find out what sort of treatment is available to keep it at bay in her chest area.  

Mum is now talking about not having any treatment as she feels fine apart from being a bit breathless, which the doctor will prescribe an inhaler for.  I have so many questions, but no one has a crystal ball.  If she doesn't have any treatment how long will she have.  If she'd never gone for a chest x-ray she would be none the wiser and just a bit breathless, which she's always attributed to her COPD.

If she has treatment will this give her more time.  Everything seems up in the air at the moment and mum is upbeat about it all.  She's only a tiny person and weighs just under 7 stone and has always found it hard to keep weight on.  She thinks any sort of treatment will make her lose the weight she has and she's heard so many horror stories.  

I'm just reaching out to see if anyone else is going through similar things.