My 79-year-old father is being treated for a lung abscess. What is this condition, and can it be cured? (Tran Long, 41, Hung Yen)

My father has end-stage lung cancer and has recently been experiencing chest pain and shortness of breath. Are these signs of metastasis to the pleura, and how is it treated? (Nguyen Van Minh, Ninh Binh)