Plural Effusion. Even in three petscan (

My relative (Female) had best cancer. Treatment completed successfully. After one year of treatment she developed collection of water (medical term Plural Effusion) in her chest. We did plurosis 3 month ago n kept watch on same. Problem is not resolved yet. Water is again observed. Dr suggested three options first observe same for more time, do again plurosis, Laproscopy. We are confused because Dr asked us to take decision. What should we do. One more thing we did petscan also three times as soon as we detected Plural Effusion. Main thing is malignant Effusion is not observed even in three petscan (thank God)... Please suggest what should we do to cure water collection in her chest.