Fatigue, excessive sweats & muscle loss for over 4 years. could it be paraneoplastic syndrome from lung cancer. ex smoker. hr ct unremarkable jul 2018

Unlikely: Lung cancer would have progressed considerably over 4 years, so that is not a likely explanation. It is not feasible to provide a meaningful opinion without additional history, physical examination and may be some tests. Counter-intuitive as it may seem, exercise may help. Start with low intensity exercise such as walking and gradually increase the intensity as tolerated.