tarasz,
I am assuming the bone tumors are metastases from his small cell lung cancer.
Since he is in stage IV and has edema around the brain, these are not good signs, as you are probably already aware of.
Swelling around the brain, usually signifies that he probably has metastases in the brain now too.
It is not possible to tell anyone how many actual months, weeks, etc they have. But, you should probably not delay is doing anything that needs to get done.
Good luck.