My mother had small cell lung cancer from smoking and working on ships loaded with asbestos during WWII. I'm sorry that I have bad news for you. My mother found out in May of 1995 that she had cancer and she was gone by August. She should never have had Chemo because all it did was make her extremely ill. The last few months of her like were horrible, she suffered terribly. Back then 1995, the chances of surviving this type of cancer was only around 5%. I'm not sure if the statistics have changed but for your sister's welfare I hope so.
My mother was my best friend and seeing her go through what she went through was terrible. My sister and brothers did not want to put her in a nursing home therefore we kept her home and took care of her ourselves and toward the end those wonderful nurses from hospice.
I wish I had better news for you. Perhaps they've made improvements on the chemo protocol and your sister has a much better chance, As I mentioned before my mother got really ill on the chemo and I think that's what ultimately killed her. Also my mother was 71, which doesn't sound old to me now as a lot of people I know are turning 70 and up. What I'm trying to say is that if your sister is fairly young I'm sure her chances will be better than my mom's.
Please kept us informed and I'll be thinking of your sister hoping that she can beat this thing.

Leslie