Talk to General Physician on Metastatic Cancer, Primary Breast

My Mother is above 70 years of Age, 1.5 month back she had shortness of breath, after that pleural Effusion has occured, and effusion has been removed by Chest Tube, and about 5_6 litres of effusion has been ejected. CT scan and cytology is showing metastatic cancer, the patient is in old age, and admitted in hospital with oxygen, and weakness. so I haven't gone for Biopsy. any Dr can treat, or give proper plan of action I am ready for online consultation of one who has understood and let me guide in Best manner. I am very upset