My dad has stage 4 nsclc, what tests he should normally do to check the progress/ regress? and how often.

It depends.: For stage 4 cancer, scans are usually done every 3-6 months. If his metastatic disease is in his bones only, scans can be done less often. Scans are also done for new or worsening symptoms. If he is receiving chemotherapy, he also needs blood tests to check his blood counts and liver functions. These should be done every 3-6 weeks depending on the drugs.