Stage 4 lung cancer with metastatic tumours

It is with a heavy heart I ask this question.

My Dad was diagnosed with stage 4 small cell lung cancer which had spread to his liver. Within a week we were told it had spread to his bones, lymph nodes and adrenal glands. He was admitted into hospital as they were worried it had also gone to his spine and brain.

Tonight we found out he does have a number of tumours along and around his spine and lesions on the brain.

They are talking about radiotherapy.

I know theres no definitive timescale but realistically are we looking at only having him with us for a short time?