Talk to Pulmonologist / Lung on Lung Biopsy Report

My father has been facing shortness of breath for last 5 months. Initially he was diagnosed with TB. However, his AFB tests were negative. He responded positively to ATT for 3 months after which progress stopped. CT Scan suggested empyema in lungs for which VATS was conducted along with pleural tissue extraction for biopsy. Biopsy report: Sections examined reveal pleural tissue with a poorly differentiated malignant neoplasm characterized by cells focally forming signet ring shaped cells. There is wide spread evidence of vascular and lymphatic premeation. The tumour cells are positive for Cytokeratin 7 and Cytokeratin 20. They are negative for TTF-1. The features are consistent with poorly differentiated metastatic adenocarcinoma. Based on morphology and irnmunohistochemical profile, possibilities include upper gastro­ intestinal tract & pancreato-biliary tract. I want to understand expected time left and way forward with quality of life being primary aim