Hello My Dad Has Stage 3 Lung Cancer. His Oncologist

Hello my dad has stage 3 lung cancer.
His oncologist has given him 12 sessions of radiotherapy.

He had a pet scan 2 months ago and has three tumours located to the right side of his lung. No other cancer cells where found.

He finished radiotheaypy 2 weeks ago but the day he finished his ankles and feet started to swell. He is also on 2mg of dexomothicin steroids. Could this be causing his swelling? Or could it mean cancer could of spread?

My dad is only 48 and I don't want to give up on him. As a nurse myself I know the future is unknown I just want the best for him. And yo be comfortable. Also he is suffering from depression quite bad. Is there anything I can do to give him a better quality of life?

He has not been "diagnosed terminal" as such but I kind of know what to expect. Is 12 sessions of radiotheaypy classed as palliative care?

Many thank sian.